S9V11F5

A thumbnail-sized Pololu buck-boost regulator that holds 5 V from any input between 2 V and 16 V, ideal for running a 5 V board from AA cells or one lithium cell.

Input voltage3 V to 16 V to start; runs down to 2 V once started
Output5 V, 3 % accuracy
Output currentUp to 1.5 A with VIN at or above VOUT; about 700 mA during start-up
Efficiency85 % to 95 % typical

Build with it in Tinkered Datasheet

S9V11F5, A thumbnail-sized Pololu buck-boost regulator that holds 5 V from any input between 2 V and 16 V, ideal for running a 5 V board from AA cells or one lithium cell.

In short

The S9V11F5 is Pololu's 5 V buck-boost regulator: it starts from 3 V, keeps running down to 2 V and accepts up to 16 V, raising or lowering the input to a steady 5 V at 85 % to 95 % typical efficiency (Pololu #2836 product page). It supplies up to 1.5 A when the input is at or above 5 V, but only about 700 mA during start-up (#2836). Three pins, VIN, GND and VOUT, plus an EN pin for sleep or a low-battery cut-off.

A buck-boost converter solves the battery problem: three AA cells start at about 4.8 V and fall to 3 V, and a lithium cell runs 4.2 V to 3 V, both straddling the 5 V a board wants. The S9V11F5 steps up or down as needed and keeps the output at 5 V within 3 % (Pololu #2836), so the board sees the same voltage from a fresh pack to a nearly empty one.

Its available current depends on the input: about 1.5 A when the input is at or above the output, less when it has to boost from a low cell, and only about 700 mA until the output first reaches 5 V (#2836). Quiescent current stays under 0.2 mA over most of the range, and soft-start ramps the output to limit inrush.

EN is pulled up to VIN through 100 kOhm and puts the regulator to sleep below 0.7 V, waking above 0.8 V (#2836). That tight threshold lets a resistor divider from VIN act as a precise low-battery cut-off, protecting lithium cells from over-discharge. There is no reverse-polarity protection on the board.

S9V11F5 pinout

Pin	Function	Type
EN	EnableSleep below 0.7 V, run above 0.8 V	input
VIN	VIN2 V to 16 V (3 V to start)	power in
GND	GND	power in
VOUT	VOUT5 V, up to 1.5 A	power out

How to wire the S9V11F5

Pin by pin, for the board you have.

S9V11F5	Arduino Uno	Note
VIN	Battery + (3 x AA)	Also to A0 directly: at most 4.8 V from three AA cells, inside the 5 V ADC range.
GND	Battery - and GND
VOUT	5V	Unplug the Uno's USB while the regulator feeds its 5V pin.
EN	not connected	Pulled up to VIN: always on.

There is no reverse-voltage protection: a battery wired backwards destroys the regulator (#2836).
With a battery pack above 5 V, divide it before A0.

Design this circuit on an Arduino Uno

S9V11F5	ESP32 DevKit V1	Note
VIN	Battery + (3 x AA or one Li-ion cell)	Also to GPIO34 through a 100 kOhm / 100 kOhm divider.
GND	Battery - and GND
VOUT	VIN
EN	not connected

Never connect VOUT (5 V) to the 3V3 pin or a GPIO.
An ESP32's Wi-Fi peaks need current: from a single cell the regulator must boost, so its available current is lower than the 1.5 A figure.

Design this circuit on an ESP32 DevKit V1

S9V11F5	Raspberry Pi Pico	Note
VIN	Battery + (3 x AA or one Li-ion cell)	Also to GP26 through a 100 kOhm / 100 kOhm divider.
GND	Battery - and GND
VOUT	VSYS	Through a Schottky diode (anode at VOUT) if USB may also be connected (Raspberry Pi Pico datasheet, p. 22).
EN	not connected

The Pico runs on VSYS from 1.8 V to 5.5 V (Pico datasheet, p. 9); the regulator mainly helps when other 5 V parts share the supply.

Design this circuit on a Raspberry Pi Pico

S9V11F5 code

Every example here compiles for its board.

No library needed

// S9V11F5 on Arduino Uno: wiring and a free simulation at https://www.tinkered.ai/components/s9v11f5
// S9V11F5 feeding an Arduino Uno's 5V pin from 3 x AA; the pack is read on A0 directly.
const int BAT_PIN = A0;
const float PACK_EMPTY = 3.0; // three AA cells at about 1.0 V each

void setup() {
  Serial.begin(115200);
  Serial.println("S9V11F5 battery monitor");
}

void loop() {
  float vbat = analogRead(BAT_PIN) * 5.0 / 1023.0; // reference is the regulated 5 V
  Serial.print("Battery: ");
  Serial.print(vbat, 2);
  Serial.println(vbat < PACK_EMPTY ? " V  replace batteries" : " V");
  delay(2000);
}

Compiled for arduino:avr:uno on 2026-10-30

No library needed

// S9V11F5 on ESP32 DevKit V1: wiring and a free simulation at https://www.tinkered.ai/components/s9v11f5
// S9V11F5 feeding an ESP32 DevKit V1 on VIN; battery read on GPIO34 through a 100k/100k divider.
const int BAT_PIN = 34;
const float PACK_EMPTY = 3.0;

void setup() {
  Serial.begin(115200);
  Serial.println("S9V11F5 battery monitor");
}

void loop() {
  float vbat = analogReadMilliVolts(BAT_PIN) * 2.0 / 1000.0; // undo the 1:2 divider
  Serial.printf("Battery: %.2f V%s\n", vbat, vbat < PACK_EMPTY ? "  replace or recharge" : "");
  delay(2000);
}

Compiled for esp32:esp32:esp32 on 2026-10-30

No library needed

// S9V11F5 on Raspberry Pi Pico: wiring and a free simulation at https://www.tinkered.ai/components/s9v11f5
// S9V11F5 feeding a Raspberry Pi Pico on VSYS; battery on GP26 through a 100k/100k divider.
const int BAT_PIN = 26;
const float PACK_EMPTY = 3.0;

void setup() {
  Serial.begin(115200);
  analogReadResolution(12); // 0..4095 over 0..3.3 V
  Serial.println("S9V11F5 battery monitor");
}

void loop() {
  float vbat = analogRead(BAT_PIN) * 3.3 / 4095.0 * 2.0;
  Serial.print("Battery: ");
  Serial.print(vbat, 2);
  Serial.println(vbat < PACK_EMPTY ? " V  replace or recharge" : " V");
  delay(2000);
}

Compiled for rp2040:rp2040:rpipico on 2026-10-30

Before you wire it

Keep VIN at or below 16 V and start it from at least 3 V (Pololu #2836).
Check polarity before connecting: the board has no reverse-voltage protection (#2836).
Expect only about 700 mA until the output reaches 5 V (#2836); large start-up loads may need to be switched on afterwards.
For lithium cells, use EN with a divider from VIN as a low-voltage cut-off (sleep below 0.7 V on EN), or use protected cells.

Don’t

Never exceed 16 V at the input; Pololu warns that higher voltages, including LC spikes from long leads, can destroy it (#2836).
Never connect VOUT to a 3.3 V pin.
Never count on 1.5 A when boosting from a low cell: the maximum current falls as the input drops below 5 V (#2836).

The regulator raises or lowers the input as needed, so a pack that falls from above 5 V to below it keeps the output at 5 V throughout (#2836).
EN's 100 kOhm pull-up draws about 10 µA per volt of VIN while asleep, about 30 µA at 3 V (#2836).
A divider from VIN to EN sets a cut-off: EN = VIN x R2/(R1 + R2), and the regulator sleeps when that falls below 0.7 V.
Long battery leads plus the board's ceramic capacitors can ring above the input voltage when power is connected (Pololu #2836 warns of LC spikes); an electrolytic capacitor across VIN and GND at the board damps them.
Quiescent current under 0.2 mA (#2836) makes it suitable for always-on battery projects.

Specifications

Input voltage: 3 V to 16 V to start; runs down to 2 V once startedPololu S9V11F5 (#2836) product page
Output: 5 V, 3 % accuracyPololu S9V11F5 (#2836) product page
Output current: Up to 1.5 A with VIN at or above VOUT; about 700 mA during start-upPololu S9V11F5 (#2836) product page
Efficiency: 85 % to 95 % typicalPololu S9V11F5 (#2836) product page
Quiescent current: Under 0.2 mA over most of the rangePololu S9V11F5 (#2836) product page
Enable: Sleep below 0.7 V, run above 0.8 V; 100 kOhm pull-up to VIN (about 10 µA per volt in sleep)Pololu S9V11F5 (#2836) product page
Protection: Short-circuit and over-temperature; no reverse-voltage protectionPololu S9V11F5 (#2836) product page
Size: 0.30 in x 0.45 in x 0.17 inPololu S9V11F5 (#2836) product page

From the Pololu 5V Step-Up/Step-Down Voltage Regulator S9V11F5 product page, published by Pololu.

Common mistakes

Reversed battery
The S9V11F5 has no reverse-voltage protection (#2836). One wrong connection kills it; add a reverse-protection module or a keyed connector.
Board resets at power-up
Start-up current is limited to about 700 mA until the output reaches 5 V (#2836). A load that draws more at switch-on, such as a servo or a large capacitor bank, can stall the start.
Expecting full current from one cell
Boosting 3.7 V to 5 V draws more input current than output current, and Pololu's maximum-current graph falls with input voltage (#2836). Budget well under 1.5 A from a single lithium cell.

S9V11F5 questions

Can the S9V11F5 run an Arduino from AA batteries?

Yes: three or four AA cells stay within its 2 V to 16 V range as they discharge, and it holds 5 V throughout (Pololu #2836). Feed VOUT to the Uno's 5V pin with USB unplugged.

What is the difference between step-up/step-down and a boost converter?

A boost converter such as the MT3608 only raises voltage, so its output follows the input once the input exceeds the set point. A buck-boost like the S9V11F5 also steps down, so a 6 V pack still gives exactly 5 V.

How do I add a low-battery cut-off?

Use a resistor divider from VIN to EN: the regulator sleeps when EN falls below 0.7 V and wakes above 0.8 V (#2836), so choose the ratio for the cell voltage where you want to stop.

How much current can it supply?

Up to 1.5 A with the input at or above 5 V, less when boosting from a lower input, and about 700 mA during start-up (#2836).

Build something with the S9V11F5

AA-powered sensor logger
Run an Arduino from three AA cells for weeks.
Build this
Portable ESP32 display
Battery-powered ESP32 clock with a low-battery warning.
Build this
Handheld Pico gadget
A Pico project that runs from AAA cells.
Build this

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S9V11F5

Reversed battery

Board resets at power-up

Expecting full current from one cell

S9V11F5 questions

AA-powered sensor logger

Portable ESP32 display

Handheld Pico gadget

What will you build with it?