MAXM17900AMB+

**EVALUATION KIT AVAILABLE** 

_Click_ _**here** for production status of specific part numbers._ 

## **MAXM17900** 

## **4V to 21V, 100mA, Compact Step-Down Power Module** 

## **General Description** 

The MAXM17900 is a step-down DC-DC power module built in a compact uSLIC™ package. The MAXM17900 integrates a controller, MOSFETs, an inductor, as well as the compensation components. The device operates from an input voltage of 4.0V to 21V, supports an adjustable output voltage from 0.9V to 5.5V, and supplies up to 100mA of load current. The high level of integration significantly reduces design complexity, manufacturing risks and offers a true “plug and play” power supply solution, hence reducing the time-to-market. 

The MAXM17900 uses peak-current-mode control and operates in pulse-width modulation (PWM) mode. 

The MAXM17900 is available in a thermally enhanced, compact 10-pin 2.6mm x 3mm x 1.5mm uSLIC package, and is rated to operate over the full -40°C to +125°C industrial/automotive temperature range. 

## **Applications** 

- Industrial Sensors 

- Motor Encoder 

- 4mA–20mA Current-Loop Powered Sensors 

## **Benefits and Features** 

- Easy to use 

   - Wide 4V to 21V Input 

   - Adjustable 0.9V to 5.5V Output 

   - ±1.75% Feedback-Voltage Accuracy 

   - Up to 100mA Output Current Capability 

   - Internally Compensated 

   - All Ceramic Capacitors, and Ultra-Compact Solution Size 

- High Efficiency 

   - Fixed-Frequency PWM 

   - Shutdown Current as Low as 1.2μA (typ) 

- Flexible Design 

   - Programmable Soft-Start and Prebias Startup 

   - Open-Drain Power Good Output ( RESET Pin) 

   - Programmable EN/UVLO Threshold 

- Robust Operation 

   - Hiccup Overcurrent Protection 

   - Overtemperature Protection 

   - -40°C to +125°C Industrial/Automotive Temperature Range 

## _**Ordering Information appears at end of data sheet.**_ 

- High-Voltage LDO Replacement 

- HVAC and Building Control 

_uSLIC is a trademark of Maxim Integrated Products, Inc._ 

## **Typical Application Circuit** 

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VIN MAXM17900 VOUT<br>10 to 21V 5V, 100mA<br>IN OUT<br>CIN COUT<br>2.2µF   EN/UVLO GND 10µF R1<br>261kΩ<br>RESET<br>FB<br>RT/SYNC R2<br>R3 LX SS 49.9kΩ<br>69.8kΩ<br>CIN = 2.2µF: C2012X7R1H225K125AC<br>COUT = 10µF: GRM21BR70J106K<br>**----- End of picture text -----**<br>


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_19-100210; Rev 0; 12/17_ 

## MAXM17900 

## 4V to 21V, 100mA, 

## Compact Step-Down Power Module 

## **Absolute Maximum Ratings** 

IN, EN/UVLO to GND ............................................-0.3V to +26V LX to GND .......................................................-0.3V to IN +0.3V OUT to GND ............................................................-0.3V to +7V RT/SYNC, SS, FB, RESET , MODE to GND ...........-0.3V to +6V Output Short-Circuit Duration ....................................Continuous 

Operating Temperature Range (Note 1) ........... -40°C to +125°C Junction Temperature ......................................................+150°C Storage Temperature Range ............................ -65°C to +125°C Lead Temperature (soldering, 10s) .................................+300°C Soldering Temperature (reflow) .......................................+260°C 

_Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability._ 

## **Package Information** 

|**Package Information**|**Package Information**|
|---|---|
|**PACKAGE TYPE: 10 uSLIC**||
|Package Code|M102A3+1|
|Outline Number|**21-100094**|
|Land Pattern Number|**90-100027**|
|**THERMAL RESISTANCE (Note 2)**||
|Junction to Ambient (θJA)|30.6°C/W|



For the latest package outline information and land patterns (footprints), go to **www.maximintegrated.com/packages** . Note that a “+”, “#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status. 

**Note 1:** Junction temperature greater than +125°C degrades operating lifetimes 

- **Note 2:** Package thermal resistance measured on Evaluation Board, Natural convection. For detailed information on package thermal considerations, refer to **www.maximintegrated.com/thermal-tutorial** . 

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## MAXM17900 

## 4V to 21V, 100mA, Compact Step-Down Power Module 

## **Electrical Characteristics** 

(VIN = 12V, VGND = 0V, VFB = 0.85V, VEN/UVLO = 1.5V, RT/SYNC = 69.8kΩ, LX = SS = RESET = unconnected; TA = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C. All voltages are referenced to GND, unless otherwise noted) (Note 3) 

|**PARAMETER**|**SYMBOL**|**CONDITIONS**|**MIN**<br>**TYP**<br>**MAX**|**UNITS**|
|---|---|---|---|---|
|**INPUT SUPPLY (IN)**|||||
|Input Voltage Range|VIN||4<br>21|V|
|Input Shutdown Current|IIN-SH|VEN/UVLO= 0V, TA= +25°C|0.5<br>1.2<br>2.25|µA|
|Input Supply Current|IQ-PWM|VFB= Normal switching, VMODE= 0V,<br>VOUT= 3.3V|800<br>1100<br>1950||
|**MODULE OUTPUT PIN (OUT)**|||||
|Output Line Regulation<br>Accuracy||VIN= 4V to 21V, VOUT= 3.3V,<br>ILOAD= 0|0.1|mV/V|
|Output Load Regulation<br>Accuracy||Tested with IOUT= 0A and 100mA<br>VOUT= 3.3V|0.3|mV/mA|
|**ENABLE/UVLO (EN/UVLO)**|||||
|EN/UVLO Threshold|VENR|VEN/UVLOrising|1.2<br>1.25<br>1.3|V|
||VENF|VEN/UVLOfalling|1.1<br>1.15<br>1.2||
||VEN-TRUESD|VEN/UVLOfalling, true shutdown|0.72||
|EN/UVLO Leakage Current|IEN|VEN/UVLO= 1.3V, TA= +25°C|-100<br>+100|nA|
|**LX**|||||
|LX Leakage Current|ILX-LKG|VEN= 0V, TA= +25°C,VLX= (VGND+ 1V)<br>to (VIN- 1V) VOUT= foat|-1<br>+1|µA|
|**SOFT-START (SS)**|||||
|Soft-Start Time|tSS|No SS cap|4.4<br>5.1<br>5.8|ms|
|SS Charging Current|ISS|VSS= 0.4V|4.7<br>5<br>5.3|µA|
|**FEEDBACK (FB)**|||||
|FB Regulation Voltage|VFB-REG||0.786<br>0.8<br>0.814|V|
|FB Input Leakage Current|IFB|VFB= 0.81V, TA= 25°C|-100<br>+120|nA|
|**CURRENT LIMIT**|||||
|VOUTCurrent-Limit|ISOURCE-LIMIT||100<br>178|mA|
|VOUTCurrent-Limit|ISINK-LIMIT||-74<br>-50|mA|



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## MAXM17900 

## 4V to 21V, 100mA, Compact Step-Down Power Module 

## **Electrical Characteristics (continued)** 

(VIN = 12V, VGND = 0V, VFB = 0.85V, VEN/UVLO = 1.5V, RT/SYNC = 69.8kΩ, LX = SS = RESET = unconnected; TA = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C. All voltages are referenced to GND, unless otherwise noted) (Note 3) 

|**PARAMETER**|**SYMBOL**|**CONDITIONS**|**MIN**|**TYP**|**MAX**|**UNITS**|
|---|---|---|---|---|---|---|
|**OSCILLATOR (RT/SYNC)**|||||||
|Switching Frequency|fSW|RRT= 422kΩ|85<br>100<br>120|||kHz|
|||RRT= 191kΩ|200<br>220<br>250||||
|||RRT= 130kΩ|295<br>322<br>350||||
|||RRT= 69.8kΩ|540<br>600<br>640||||
|||RRT= 45.3kΩ|813<br>900<br>973||||
|Switching Frequency<br>Adjustable Range||See the_Switching Frequency (RT/SYNC)_<br>section for details|100<br>900|||kHz|
|SYNC Input Frequency|||1.1 x<br>fSW<br>900|||kHz|
|SYNC Pulse Minimum<br>Of-Time|||40|||ns|
|SYNC Rising Threshold|VSYNC-H||1<br>1.22<br>1.48|||V|
|Hysteresis|VSYNC-HYS||0.110<br>0.18<br>0.268||||
|Number of SYNC Pulses to<br>Enable Synchronization|||1|||Cycles|
|**TIMING**|||||||
|Minimum On-Time|tON-MIN||46<br>90<br>150|||ns|
|Maximum Duty Cycle|DMAX|VFB= 0.98 x VFB-REG<br>FSW= 600kHz|90<br>94<br>98|||%|
|||600kHz < fSW< 900kHz,<br>VFB= 0.98 x VFB-REG|87<br>92||||
|Hiccup Timeout|||51|||ms|
|**RESET**|||||||
|FB Threshold forRESET<br>Rising|VFB-OKR|VFBrising|93<br>95<br>97|||%|
|FB Threshold forRESET<br>Falling|VFB-OKF|VFBfalling|90<br>92<br>94|||%|
|RESETDelay after FB<br>Reaches 95% Regulation|||2.08|||ms|
|RESETOutput Level Low||IRESET= 1mA|0.23|||V|
|RESETOutput Leakage<br>Current||VFB= 1.01 x VFB-REG,TA= +25°C|1|||µA|
|**THERMAL SHUTDOWN**|||||||
|Thermal-Shutdown Threshold||Temperature rising|160|||°C|
|Thermal-Shutdown Hysteresis|||20|||°C|



**Note 3:** All limits are 100% tested at +25°C. Limits over temperature are guaranteed by design. 

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## MAXM17900 

## 4V to 21V, 100mA, Compact Step-Down Power Module 

## **Typical Operating Characteristics** 

(VIN = 12V, VEN/UVLO = 1.5V, RT/SYNC = 69.8kΩ, TA = +25°C unless otherwise noted) 

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EFFICIENCY VS. LOAD CURRENT EFFICIENCY VS. LOAD CURRENT<br>(3.3V OUTPUT, PWM MODE, fSW = 600kHz)  (5V OUTPUT, PWM MODE, fSW = 600kHz)<br>100 toc01 100 toc02<br>9080 TETLo  TT 9080 TTTTT]<br>70 Ke ee TTT 70 |WANTAoNTT<br>60 60 VIN = 21V<br>50 MAAN VIN  E  = 21V E 50 HN VIN = 10V dH<br>40 HANESWK! VIN = 12V PEER 40 HEl/l LNTNUE VIN = 12V il<br>30 HLA ULE 30 WL<br>2010 WLPELLET VIN = 6V EETEEE] 2010 LEEEEEET]<br>0 20 40 60 80 100 0 20 40 60 80 100<br>LOAD CURRENT (mA) LOAD CURRENT (mA)<br>LOAD AND LINE REGULATION SOFT-START FROM EN/UVLO<br>5.05 (5V OUTPUT, PWM MODE) toc04 (3.3V OUTPUT, 100mALOAD CURRENT, PWM MODE) toc05<br>5.00<br>4.95 VEN/UVLO 5V/div<br>4.90 VIN = 21V<br>1V/div<br>4.85 VIN = 12V VIN = 10V<br>VOUT<br>4.80 IOUT 50mA/div<br>4.75 VRESET 5V/div<br>4.70 1ms/div<br>0 10 20 30 40 50 60 70 80 90 100<br>LOAD CURRENT (mA)<br>EFFICIENCY (%) EFFICIENCY (%)<br>OUTPUT  VOLTAGE (V)<br>**----- End of picture text -----**<br>


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LOAD AND LINE REGULATION<br>(3.3V OUTPUT, PWM MODE)<br>3.350 toc03<br>3.345 VIN = 6V VIN = 21V<br>3.340<br>3.335<br>l<br>3.330<br>3.325<br>MTT<br>3.320<br>VIN = 12V I<br>3.315<br>3.310<br>3.305<br>3.300<br>0 10 20 30 40 50 60 70 80 90 100<br>LOAD CURRENT (mA)<br>OUTPUT  VOLTAGE (V)<br>**----- End of picture text -----**<br>


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SOFT-START FROM EN/UVLO<br>(5V OUTPUT, 100mALOAD CURRENT, PWM MODE)<br>toc06<br>VEN/UVLO 5V/div<br>VOUT 2V/div<br>IOUT 50mA/div<br>VRESET 5V/div<br>1ms/div<br>**----- End of picture text -----**<br>


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SHUTDOWNFROM EN/UVLO SOFT-START WITH 3V PREBIAS  SOFT-START WITH 3V PREBIAS<br>(5V OUTPUT, 100mA LOAD CURRENT, PWM MODE) (5V OUTPUT, NO LOAD ) (100mA LOAD CURRENT, 5V OUTPUT, PWM MODE)<br>toc07 toc08 toc09<br>VEN/UVLO<br>5V/div VEN/UVLO 5V/div VEN/UVLO 5V/div<br>VOUT 1V/div 2V/div<br>VOUT<br>100mA/div<br>IOUT 2V/div IOUT<br>VRESET 2V/div<br>VRESET 50mA/div VOUT<br>5V/div VRESET 5V/div 1ms/div<br>1ms/div 1ms/div<br>**----- End of picture text -----**<br>


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## MAXM17900 

## 4V to 21V, 100mA, Compact Step-Down Power Module 

## **Typical Operating Characteristics (continued)** 

(VIN = 12V, VEN/UVLO = 1.5V, RT/SYNC = 69.8kΩ, TA = +25°C unless otherwise noted) 

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STEADY-STATE SWITCHING WAVEFORMS  STEADY-STATE SWITCHING WAVEFORMS<br>(5V OUTPUT, NO LOAD CURRENT) (5V OUTPUT, 0.1A LOAD CURRENT) AVERAGE CURRENT LIMIT<br>toc10 toc11 240 toc12<br>H M<br>230<br>V(AC)OUT 10mV/div V(AC)OUT 10mV/div 220 TEMP = 85 ° C<br>210<br>200 ONES et<br>~<a my me phim ty hy 190 .>>-~—— anne<br>180 TEMP = 25 ° C<br>5V/div VLX 5V/div 170<br>VLX Sa tl a ps ek ge oe mt pe ae em el tig es TEMP = -40 piipit ° C<br>160<br>2 μ s/div 2 μ s/div 0 5 10 15 20 25<br>INPUT VOLTAGE (V)<br>AVERAGE CURRENT LIMIT (mA)<br>**----- End of picture text -----**<br>


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SWITCHING FREQUENCY  SHUTDOWN CURRENT<br>VS. INPUT VOLTAGE VS. INPUT VOLTAGE<br>630 toc13 3.00 toc14<br>620 2.50<br>610<br>2.00 25°C<br>600<br>1.50<br>590<br>-40°C<br>25°C 1.00<br>580 85°C<br>570 0.50 TEMP = 25 ° C<br>560 0.00 tt<br>0 5 10 15 20 25 0 5 10 15 20 25<br>INPUT VOLTAGE (V) INPUT VOLTAGE (V)<br>LOAD CURRENT TRANSIENT RESPONSE LOAD CURRENT TRANSIENT RESPONSE<br>(VIN = 12V, VOUT = 3.3V, IOUT = 0.05A TO 0.IN = 12V, VOUT = 3.3V, IOUT = 0.05A TO 0. = 12V, VOUT = 3.3V, IOUT = 0.05A TO 0.OUT = 3.3V, IOUT = 0.05A TO 0. = 3.3V, IOUT = 0.05A TO 0.OUT = 0.05A TO 0. = 0.05A TO 0. 1 A) (VIN = 12V, VOUT = 5V, IOUT = 0A TO 0.05A)IN = 12V, VOUT = 5V, IOUT = 0A TO 0.05A) = 12V, VOUT = 5V, IOUT = 0A TO 0.05A)OUT = 5V, IOUT = 0A TO 0.05A) = 5V, IOUT = 0A TO 0.05A)OUT = 0A TO 0.05A) = 0A TO 0.05A)<br>toc16 toc17<br>SWITCHING FREQUENCY (kHz) sHUTDOWN CURRENT (uA)<br>**----- End of picture text -----**<br>


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LOAD CURRENT TRANSIENT RESPONSE LOAD CURRENT TRANSIENT RESPONSE<br>(VIN = 12V, VOUT = 3.3V, IOUT = 0.05A TO 0.IN = 12V, VOUT = 3.3V, IOUT = 0.05A TO 0. = 12V, VOUT = 3.3V, IOUT = 0.05A TO 0.OUT = 3.3V, IOUT = 0.05A TO 0. = 3.3V, IOUT = 0.05A TO 0.OUT = 0.05A TO 0. = 0.05A TO 0. 1 A) (VIN = 12V, VOUT = 5V, IOUT = 0A TO 0.05A)IN = 12V, VOUT = 5V, IOUT = 0A TO 0.05A) = 12V, VOUT = 5V, IOUT = 0A TO 0.05A)OUT = 5V, IOUT = 0A TO 0.05A) = 5V, IOUT = 0A TO 0.05A)OUT = 0A TO 0.05A) = 0A TO 0.05A)<br>toc16 toc17<br>50mV/div<br>VOUT (AC<br>50mV/div  COUPLED)<br>VOUT (AC COUPLED) ( souene<br>: }<br>IOUT 50mA/div<br>IOUT 50mA/div<br>a<br>200µs/div 100µs/div<br>**----- End of picture text -----**<br>


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LOAD CURRENT TRANSIENT RESPONSE<br>(VIN = 12V, VOUT = 5V, IOUT = 0.05A TO 0.1A)<br>toc15<br>50mV/div<br>VOUT (AC<br>COUPLED)<br>IOUT 50mA/div<br>100µs/div<br>**----- End of picture text -----**<br>


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LOAD CURRENT TRANSIENT RESPONSE<br>(VIN = 12V, VOUT = 3.3V, IOUT = 0A TO 0.05A)<br>toc18<br>VOUT 50mV/div<br>(AC<br>COUPLED)<br>|<br>t<br>IOUT 50mA/div<br>200µs/div<br>**----- End of picture text -----**<br>


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## MAXM17900 

## 4V to 21V, 100mA, Compact Step-Down Power Module 

## **Typical Operating Characteristics (continued)** 

(VIN = 12V, VEN/UVLO = 1.5V, RT/SYNC = 69.8kΩ, TA = +25°C unless otherwise noted) 

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EXTERNAL SYNCHRONIZATION WITH 900kHz<br>CLOCK FREQUENCY OUTPUT CURRENT<br>DURING STEADY-STATE SHORT OVERLOAD PROTECTION<br>(VIN = 12V, VOUT = 5V, IOUT = 0.1A) toc19 toc20 toc21<br>VLX 5V/div<br>VOUT 2V/div<br>LUAU<br>VSYNC 2V/div IOUT 100mA/div<br>anneanmantnn — —— LX : 5V/div<br>2µs/div 20ms/div 40µs/div<br>**----- End of picture text -----**<br>


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BODE PLOT<br>(VIN = 12V,  VOUT = 5V, IOUT = 0.1A)<br>40 toc22 100<br>30 90<br>|<br>80<br>20 PHASE<br>70<br>10 yoRP Tre 60<br>0 PL SN LET 50<br>TIPN STH<br>-10 GAIN 40<br>30<br>-20 EElll N ME<br>-30 fPHASE MARGIN = 67.8CR = 23.2kHz,  ° 2010<br>-40 enna,ll 0<br>10 [3] 10 [4] 10 [5]<br>FREQUENCY (Hz)<br>GAIN (dB) ) ° PHASE (<br>**----- End of picture text -----**<br>


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BODE PLOT<br>(VIN = 12V, VOUT = 3.3V, IOUT = 0.1A)<br>40 toc23 90<br>30 PHASE 80<br>I<br>20 70<br>10 Pope THT SAT 60<br>50<br>0 Pt PAT TN UT<br>PIA 40<br>-10 GAIN<br>30<br>-20 annalslll HIN) 20<br>-30 fPHASE MARGIN = 66.2CR = 28.1kHz,  ° 10<br>-40 fbfBilli 0<br>10 [3] 10 [4] 10 [5]<br>FREQUENCY (Hz)<br>GAIN (dB) ) ° PHASE (<br>**----- End of picture text -----**<br>


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## MAXM17900 

## 4V to 21V, 100mA, Compact Step-Down Power Module 

## **Pin Configuration** 

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TOP VIEW<br>LX 1 + 10 IN<br>GND 2 9 EN/UVLO<br>MAXM17900<br>GND 3 8 RT/SYNC<br>RESET 4 7 SS<br>OUT 5 6 FB<br>‘+’ INDICATES PIN 1 OF THE MODULE<br>**----- End of picture text -----**<br>


## **Pin Description** 

|**PIN NAME**|**PIN #**|**FUNCTION**|
|---|---|---|
|LX|1|Switching Node. LX is high impedance when the device is in shutdown. Do not connect any external<br>components to this pin.|
|GND|2, 3|Ground. Connect GND to the power ground plane. Connect all the circuit ground connections together<br>at a single point. See the_PCB Layout Guidelines_ section.|
|RESET|4|Open-Drain Reset Output. Pull upRESETto an external power supply less than or equal to 5.5V with<br>an external resistor.RESETpulls low if FB drops below 92% of its set value.RESETgoes high 2ms<br>after FB rises above 95% of its set value.|
|OUT|5|Module output pin. Connect a capacitor from OUT to GND. See _PCB Layout Guidelines_ section for<br>more connection details.|
|FB|6|Output Feedback Connection. Connect FB to a resistor-divider between OUT and GND to set the<br>output voltage.|
|SS|7|Soft-Start Capacitor Input. Connect a capacitor from SS to GND to set the soft-start time. Leave SS<br>unconnected for default 5.1ms internal soft-start.|
|RT/SYNC|8|Oscillator Timing Resistor Input. Connect a resistor from RT/SYNC to GND to program the switching<br>frequency from 100kHz to 900kHz. See the_Switching Frequency (RT/SYNC)_ section for details. An<br>external pulse can be applied to RT/SYNC through a coupling capacitor to synchronize the internal<br>clock to the external pulse frequency.|
|EN/UVLO|9|Active-High, Enable/Undervoltage-Detection Input. Pull EN/UVLO to GND to disable the module<br>output. Connect EN/UVLO to IN for always-on operation. Connect a resistor-divider between IN, EN/<br>UVLO, and GND to program the input voltage at which the module is enabled and turns on.|
|IN|10|Power Module Input. Connect a ceramic capacitor from IN to GND for bypassing. Place the capacitor<br>close to the IN and PGND pins. See_Component Selection_tables for more details.|



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## MAXM17900 

## 4V to 21V, 100mA, Compact Step-Down Power Module 

## **Functional Diagram** 

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MAXM17900<br>IN<br>LDO<br>HIGH-SIDE DRIVER<br>RT/SYNC OSCILLATOR LX<br>PEAK<br>CURRENT-MODE 100µH<br>CONTROLLER O UT<br>EN/UVLO<br>1.25V LOW-SIDE DRIVER<br>GND<br>SS<br>RESET<br>FB<br>PGOOD LOGIC<br>0.76V<br>**----- End of picture text -----**<br>


## **Detailed Description** 

The MAXM17900 synchronous step-down power module with integrated MOSFETs and inductor, operates over a 4V to 21V input voltage range. The module can deliver output current up to 100mA at output voltages of 0.9V to 5.5V. The feedback voltage is accurate to within ±1.75% over -40°C to +125°C. 

The device uses an internally-compensated, peak current mode control architecture. On the rising edge of the internal clock, the high-side pMOSFET turns on. An internal error amplifier compares the feedback voltage to a fixed internal reference voltage and generates an error 

voltage. The error voltage is compared to a sum of the current-sense voltage and a slope-compensation voltage by a PWM comparator to set the “on-time.” During the on-time of the pMOSFET, the inductor current ramps up. For the remainder of the switching period (off-time), the pMOSFET is kept off and the low-side nMOSFET turns on. During the off-time, the inductor releases the stored energy as the inductor current ramps down, providing current to the output. Under overload conditions, the cycleby-cycle current- limit feature limits inductor peak current by turning off the high-side pMOSFET and turning on the low-side nMOSFET. 

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4V to 21V, 100mA, Compact Step-Down Power Module 

## MAXM17900 

## **Enable Input (EN/UVLO) and Soft-Start (SS)** 

When EN/UVLO voltage increases above 1.25V (typ), the device initiates a soft-start sequence and the duration of the soft-start depends on the status of the SS pin voltage at the time of power-up. If the SS pin is not connected, the device uses a fixed 5.1ms (typ) internal soft-start to ramp up the internal error-amplifier reference. If a capacitor is connected from SS to GND, a 5μA current source charges the capacitor and ramps up the SS pin voltage. The SS pin voltage is used as a reference for the internal error amplifier. Such a reference ramp up allows the output voltage to increase monotonically from zero to the final set value independent of the load current. 

EN/UVLO can be used as an input voltage UVLO adjustment input. An external voltage-divider between IN and EN/UVLO to GND adjusts the input voltage at which the device turns on or off. See the _Setting the Input Undervoltage-Lockout Level_ section for details. If input UVLO programming is not desired, connect EN/UVLO to IN (see the _Electrical Characteristics_ table for EN/UVLO rising and falling-threshold voltages). Driving EN/UVLO low disables both power MOSFETs, as well as other internal circuitry, and reduces IN quiescent current to below 1.2μA. The SS capacitor is discharged with an internal pulldown resistor when EN/UVLO is low. If the EN/UVLO pin is driven from an external signal source, a series resistance of minimum 1kΩ is recommended to be placed between the signal source output and the EN/UVLO pin, to reduce voltage ringing on the line. 

## **Switching Frequency (RT/SYNC)** 

Switching frequency of the device can be programmed from 100kHz to 900kHz by using a resistor connected from RT/SYNC to GND. The switching frequency (fSW) is related to the resistor connected at the RT/SYNC pin (RT) by the following equation, where RT is in kΩ and fSW is in kHz: 

**==> picture [54 x 25] intentionally omitted <==**

## **External Synchronization** 

The RT/SYNC pin can be used to synchronize the device’s internal oscillator to an external system clock. The external clock should be coupled to the RT/SYNC pin through a 47pF capacitor, as shown in Figure 1. The external clock logic high level should be higher than 3V, logic low level lower than 0.5V and the duty cycle of the external clock should be in the range of 10% to 70%. The RT resistor should be selected to set the switching frequency 10% lower than the external clock frequency. The external clock should be applied at least 500μs after enabling the device for proper configuration of the internal loop compensation. 

## **Reset Output ( RESET )** 

The device includes an open-drain RESET output to monitor output voltage. RESET should be pulled up with an external resistor to the desired external power supply less than or equal to 5.5V. RESET goes high impedance 2ms after the output rises above 95% of its nominal set value and pulls low when the output voltage falls below 92% of the set nominal output voltage. RESET asserts low during the hiccup timeout period. 

**==> picture [242 x 182] intentionally omitted <==**

**----- Start of picture text -----**<br>
MAXM17900<br>47pF<br>RT/SYNC<br>CLOCK<br>SOURCE RT<br>VLOGIC-HIGH<br>VLOGIC-LOW<br>DUTY<br>**----- End of picture text -----**<br>


_Figure 1. Synchronization to an External Clock_ 

The switching frequency in ranges of 130kHz to 160kHz and 230kHz to 280kHz are not allowed for user programming to ensure proper configuration of the internal adaptive-loop compensation scheme. 

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4V to 21V, 100mA, Compact Step-Down Power Module 

## MAXM17900 

## **Startup Into a Pre-biased Output** 

The device supports monotonic startup into a pre-biased output. When the module starts into a pre-biased output, both the high-side and low-side switches are turned off so that the module does not sink current from the output. High-side and low-side switches do not start switching until the PWM comparator commands the first PWM pulse, at which point switching commences. The output voltage is then smoothly ramped up to the target value in alignment with the internal reference. Such a feature is useful in applications where digital integrated circuits with multiple rails are powered. 

## **Operating Input-Voltage Range** 

The maximum operating input voltage is determined by the minimum controllable on-time, while the minimum operating input voltage is determined by the maximum duty cycle and circuit voltage drops. The minimum and maximum operating input voltages for a given output voltage should be calculated as follows: 

**==> picture [193 x 67] intentionally omitted <==**

where, 

VOUT = Steady-state output voltage 

IOUT = Maximum load current 

fSW = Switching frequency (max) 

DMAX = Maximum duty cycle 

tON(MIN) = Worst case minimum controllable switch ontime (152ns). 

## **Overcurrent Protection (OCP), Hiccup Mode** 

The device implements a HICCUP-type overload protection scheme to protect the inductor and internal FETs under output short-circuit conditions. When the overcurrent event occurs, the part enters hiccup mode. In this mode, the part is initially operated with hysteretic cycleby-cycle peak-current limit that continues for a time period equal to twice the soft-start time. The part is then turned off for a fixed 51ms hiccup timeout period. This sequence of hysteretic inductor current waveforms, followed by a hiccup timeout period, continues until the short/overload 

on the output is removed. Since the inductor current is bound between two limits, inductor current runway never happens. 

## **Thermal Shutdown** 

Thermal shutdown limits the total power dissipation in the module. When the junction temperature exceeds +160°C, an on-chip thermal sensor shuts down the device, turns off the internal power MOSFETs, allowing the device to cool down. The device turns on after the junction temperature cools by approximately 20°C. 

## **Application Information** 

## **Input Capacitor Selection** 

Small ceramic input capacitors are recommended. The input capacitor reduces peak current drawn from the power source and reduces noise and voltage ripple on the input caused by the switching circuitry. It is recommended to select the input capacitor of the module to keep the input-voltage ripple under 2% of the minimum input voltage, and to meet the maximum ripple-current requirements. 

## **Output Capacitor Selection** 

Small ceramic X7R-grade output capacitors are recommended for the device. The output capacitor has two functions. It stores sufficient energy to support the output voltage under load transient conditions and stabilizes   the device’s internal control loop. Usually the output capacitor is sized to support a step load of 50% of the maximum output current in the application, such that the output voltage deviation is less than 3%. Calculate the minimum required output capacitance from the following equations: 

|**FREQUENCY RANGE**<br>**(kHZ)**|**MINIMUM OUTPUT**<br>**CAPACITANCE (µF)**|**MINIMUM OUTPUT**<br>**CAPACITANCE (µF)**|
|---|---|---|
|100 to 130||OUT<br>50<br>V|
|160 to 230||OUT<br>25<br>V|
|280 to 900||OUT<br>17<br>V|



It should be noted that dielectric materials used in ceramic capacitors exhibit capacitance loss due to DC bias levels and should be appropriately de-rated to ensure the required output capacitance is obtained in the application. 

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4V to 21V, 100mA, Compact Step-Down Power Module 

## MAXM17900 

## **Soft Start Capacitor Selection** 

The device offers a 5.1ms internal soft-start when the SS pin is left unconnected.  When adjustable soft-start time is required, connect a capacitor from SS to GND to program the soft-start time. The minimum soft-start time is related to the output capacitance (COUT) and the output voltage (VOUT) by the following equation: 

**==> picture [115 x 10] intentionally omitted <==**

where tSS is in milliseconds and COUT is in µF. 

Soft-start time (tSS) is related to the capacitor connected at SS (CSS) by the following equation: 

**==> picture [73 x 10] intentionally omitted <==**

where tSS is in milliseconds and CSS is in nanofarads. 

## **Setting the Input Undervoltage-Lockout Level** 

The device offers an adjustable input undervoltage-lockout level. Set the voltage at which the device turns on with a resistive voltage-divider connected from IN to GND (see Figure 2). Connect the center node of the divider to EN/ UVLO. Choose R1 to be 3.3MΩ max and then calculate R2 as follows: 

**==> picture [74 x 24] intentionally omitted <==**

where VINU is the voltage at which the device is required to turn on. 

## **Adjusting the Output Voltage** 

The output voltage can be programmed from 0.9V to 5.5V. Different output voltage needs to use different switching frequency (see Table 1). Set the output voltage by connecting a resistor-divider from output to FB to GND (see Figure 3). Choose R5 in the range of 25kΩ to 100kΩ and calculate R4 with the following equation: 

**==> picture [242 x 182] intentionally omitted <==**

**----- Start of picture text -----**<br>
VIN<br>IN<br>MAXM17900<br>R1<br>EN/UVLO<br>R2<br>GND<br>**----- End of picture text -----**<br>


_Figure 2. Adjustable EN/UVLO Network_ 

**==> picture [242 x 183] intentionally omitted <==**

**----- Start of picture text -----**<br>
VOUT<br>MAXM17900<br>R4<br>FB<br>R5<br>GND<br>**----- End of picture text -----**<br>


_Figure 3 Circuit for Setting the Output Voltage._ 

**==> picture [84 x 23] intentionally omitted <==**

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## MAXM17900 

## 4V to 21V, 100mA, Compact Step-Down Power Module 

**Table 1. Selection Component Values** 

|**VOUT (V)**|**VIN (V)**|**CIN**|**fSW (kHz)**|**RT (kΩ)**|**RT (kΩ)**|**RT (kΩ)**|**COUT**|
|---|---|---|---|---|---|---|---|
|0.9|4 to 21|1 × 2.2μF 1206 50V X7R|220|191|6.19|49.9|2 × 10μF 0805 6.3V X7R|
|1.2|4 to 21|1 × 2.2μF 1206 50V X7R|220|191|24.9|49.9|2 × 10μF 0805 6.3V X7R|
|1.5|4 to 21|1 × 2.2μF 1206 50V X7R|300|140|43.2|49.9|1 × 10μF 0805 6.3V X7R|
|1.8|4 to 21|1 × 2.2μF 1206 50V X7R|300|140|61.9|49.9|1 × 10μF 0805 6.3V X7R|
|2.5|4.5 to 21|1 × 1μF 1206 50V X7R|400|105|107|49.9|1 × 10μF 0805 6.3V X7R|
|3.3|6 to 21|1 × 1μF 1206 50V X7R|600|70|158|49.9|1 × 10μF 0805 6.3V X7R|
|5|10 to 21|1 × 1μF 0805 50V X7R|600|70|261|49.9|1 × 10μF 0805 6.3V X7R|
|5.5|10 to 21|1 × 1μF 0805 50V X7R|700|60|294|49.9|1 × 10μF 0805 10V X7R|



## **Transient Protection** 

In applications where fast line transients or oscillations with a slew rate in excess of 15V/µs are expected during power-up or steady-state operation, the MAXM17900 should be protected with a series resistor that forms a low pass filter with the input ceramic capacitor (Figure 4). These transients can occur in conditions such as hot-plugging from a low-impedance source or due to inductive load switching and surges on the supply lines. 

## **Power Dissipation** 

Ensure that the junction temperature of the devices do not exceed 125°C under the operating conditions specified for the power supply. At a particular operating condition, the power losses that lead to temperature rise of the device are estimated as follows: 

**==> picture [91 x 38] intentionally omitted <==**

where POUT is the output power, η is the efficiency of power conversion. See the _Typical Operating Characteristics_ for the power-conversion efficiency or 

**==> picture [242 x 141] intentionally omitted <==**

**----- Start of picture text -----**<br>
4.7Ω<br>IN<br>MAXM17900<br>CIN = 2.2µF<br>GND<br>**----- End of picture text -----**<br>


_Figure 4. Circuit for Transient Protection_ 

measure the efficiency to determine the total power dissipation.  The junction temperature (TJ) of the device can be estimated at any ambient temperature (TA) from the following equation: 

**==> picture [97 x 11] intentionally omitted <==**

where θJA is the junction-to-ambient thermal impedance of the package. 

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Compact Step-Down Power Module 

## MAXM17900 

## **PCB Layout Guidelines** 

Careful PCB layout (Figure 5) is critical to achieve clean and stable operation. The switching power stage requires particular attention. Follow these guidelines for good PCB layout: 

- Place the input ceramic capacitor as close as possible to VIN and GND pins 

- Ensure that all feedback connections are short and direct 

- Route high-speed switching node (LX) away from the signal pins 

For a sample PCB layout that ensures the first-pass success, refer to the MAXM17900 evaluation kit data sheet. 

**==> picture [504 x 424] intentionally omitted <==**

**----- Start of picture text -----**<br>
VIN IN OUT VOUT<br>CIN R1 MAXM17900 R6 R4 COUT<br>LX RESET<br>EN/UVLO FB<br>R2 SS RT/SYNC<br>R5<br>GND<br>R3<br>GND PLANE CIN VIN PLANE<br>+<br>1LX MAXM17900 10 IN<br>R1<br>GND 2 9 EN/UVLO<br>GND 3 8 RT/SYNC R2<br>RESET COUT 4 7SS R3<br>R6<br>OUT 5 6<br>FB<br>R5<br>VOUTPLANE R4 GND PLANE<br>VIAS TO BOTTOM SIDE GROUND PLANE<br>**----- End of picture text -----**<br>


_Figure 5. Layout Guidelines_ 

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## MAXM17900 

4V to 21V, 100mA, Compact Step-Down Power Module 

## **Ordering Information** 

|**PART**|**TEMP RANGE**|**PIN-PACKAGE**|
|---|---|---|
|MAXM17900AMB+|-40°C to +125°C|10 uSLIC|



_+Denotes a lead(Pb)-free/RoHS-compliant package._ 

## **Chip Information** 

PROCESS: BiCMOS 

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## MAXM17900 

## 4V to 21V, 100mA, Compact Step-Down Power Module 

## **Revision History** 

|**Revision**|**History**|||
|---|---|---|---|
|**REVISION**<br>**NUMBER**|**REVISION**<br>**DATE**|**DESCRIPTION**|**PAGES**<br>**CHANGED**|
|0|12/17|Initial release|—|



For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com. 

_Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits) shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance._ 

© 2017 Maxim Integrated Products, Inc.  │ 16 

Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.