L7981

STMicroelectronics

-40℃~+150℃@(TJ) 1 1MHz 3A 4.5V~28V 600mV~28V Adjustable Buck Buck Built-in No VFQFPN-8(3x3) DC-DC Converters ROHS

Extended

Category: DC DC Converters
Package: VFQFPN-8(3x3)
Pins: 9

Overview

The L7981 is a DC DC Converter made by STMicroelectronics in a VFQFPN-8(3x3) package with 9 pins. -40℃~+150℃@(TJ) 1 1MHz 3A 4.5V~28V 600mV~28V Adjustable Buck Buck Built-in No VFQFPN-8(3x3) DC-DC Converters ROHS.

PCBKit's library has its KiCad symbol (EasyEDA_Cloud:L7980TR, from EasyEDA) and its footprint (EasyEDA_Cloud:VFQFPN-8_L3.0-W3.0-P0.50-TL-EP, from EasyEDA), ready for a KiCad board. 5 are in stock at JLCPCB (part C2071852).

Symbol

EasyEDA_Cloud:L7980TRFrom EasyEDA

Footprint

EasyEDA_Cloud:VFQFPN-8_L3.0-W3.0-P0.50-TL-EPFrom EasyEDA

From the datasheet

Supply, least: 4.5 V · VCC, recommended operating min · p. 6
Supply, most: 28 V · VCC, recommended operating max · p. 6
Supply, absolute maximum: 30 V · Vcc, absolute maximum · p. 5
Junction, hottest: 150 °C · Junction temperature absolute maximum · p. 5
Takes working: 2.4 mA · VCC quiescent current max, duty cycle = 0, VFB = 0.8 V · p. 6
Takes asleep: 20 µA · Total standby quiescent current typical · p. 6
Gives: 3 A · Rated DC output current · p. 1
Current limit: 4.2 A · Maximum limiting current typical · p. 6
Feedback reference: 600 mV · Feedback voltage typical, 4.5 V < VCC < 28 V · p. 6
Switches at: 250 kHz · Free-running switching frequency typical · p. 6
Junction to air (VFQFPN): 60 K/W · Junction to ambient maximum, mounted on demonstration board · p. 5

What it is and has

DC output current: 3 A · p. 1
Input voltage: 4.5 V to 28 V · p. 1
Adjustable output voltage: From 0.6 V · p. 1
Startup and enable: Internal soft-start and enable · p. 1
Duty cycle: 100% duty cycle, low dropout operation · p. 1
Voltage feed-forward: Supported · p. 1
Zero load current operation: Supported · p. 1
Protection: Overcurrent and thermal protection · p. 1
Package options: VFQFPN 3 x 3 - 8L and HSOP8 · p. 1
Output voltage: Adjustable from 0.6 V · p. 1
LED driving: Suitable · p. 1

Around it

cap 220 nF - 1 µF: between VCC and GND; Optional bypass capacitor for high-frequency noise filtering; place as close as possible to the input voltage pin. · p. 28
ind 18 H: between OUT and VOUT; Example minimum inductance for VOUT = 5 V, VIN = 24 V, IO = 3 A, FSW = 250 kHz and current ripple equal to 30% of IO. · p. 17

Specifications

Parameter	Conditions	As printed	Page
Input voltage Vcc		max 30 V	5
Output DC voltage OUT	Upper limit: VCC	min -0.3 V	5
Analog pin FSW, COMP, SYNCH		min -0.3 · max 4 V	5
Enable pin EN	Upper limit: VCC	min -0.3 V	5
Feedback voltage FB		min -0.3 · max 1.5 V	5
Power dissipation PTOT	VFQFPN; at TA < 60 °C	max 1.5 W	5
Junction temperature range TJ		min -40 · max 150 °C	5
Storage temperature range Tstg		min -55 · max 150 °C	5
Maximum thermal resistance junction ambient RthJA	VFQFPN; package mounted on demonstration board	max 60 °C/W	5
Operating input voltage range VCC	TJ = -40 to +125 °C	min 4.5 · max 28 V	6
Turn on VCC threshold VCCON	TJ = -40 to +125 °C	max 4.4 V	6
VCC UVLO hysteresis VCCHYS	TJ = -40 to +125 °C; VCC = 12 V	min 0.12 · max 0.35 V	6
Mosfet on resistance RDSON	TJ = 25 °C; VCC = 12 V	typ 160 · max 180 m	6
Mosfet on resistance RDSON	TJ = -40 to +125 °C; VCC = 12 V	typ 160 · max 250 m	6
Maximum limiting current ILIM	TJ = 25 °C; VCC = 12 V	min 3.7 · typ 4.2 · max 4.7 A	6
Switching frequency FSW	TJ = 25 °C; VCC = 12 V	min 225 · typ 250 · max 275 KHz	6
Switching frequency FSW	TJ = -40 to +125 °C; VCC = 12 V	min 220 · max 275 KHz	6
FSW pin voltage VFSW	TJ = 25 °C; VCC = 12 V	typ 1.254 V	6
Duty cycle D	TJ = 25 °C; VCC = 12 V	min 0 · max 100 %	6
Adjustable switching frequency FADJ	RFSW = 33 k; TJ = 25 °C; VCC = 12 V	typ 1000 KHz	6
Feedback voltage VFB	4.5 V < VCC < 28 V; TJ = -40 to +125 °C	min 0.593 · typ 0.6 · max 0.607 V	6
Quiescent current IQ	Duty cycle = 0, VFB = 0.8 V; TJ = 25 °C; VCC = 12 V	max 2.4 mA	6
Total standby quiescent current IQST-BY	TJ = 25 °C; VCC = 12 V	typ 20 · max 30 A	6
EN threshold voltage	Device OFF level; TJ = 25 °C; VCC = 12 V	max 0.3 V	6
EN threshold voltage	Device ON level; TJ = 25 °C; VCC = 12 V	min 1.2 V	6
EN current	EN = VCC; TJ = 25 °C; VCC = 12 V	typ 7.5 · max 10 A	6
Soft-start duration TSS	FSW pin floating; TJ = 25 °C; VCC = 12 V	min 7.4 · typ 8.2 · max 9.1 ms	6
High level output voltage VCH	VFB < 0.6 V; TJ = 25 °C; VCC = 12 V	min 3 V	6
Low level output voltage VCL	VFB > 0.6 V; TJ = 25 °C; VCC = 12 V	max 0.1 V	6
Source COMP pin IO SOURCE	VFB = 0.5 V, VCOMP = 1 V; TJ = 25 °C; VCC = 12 V	typ 17 mA	6
Sink COMP pin IO SINK	VFB = 0.7 V, VCOMP = 1 V; TJ = 25 °C; VCC = 12 V	typ 25 mA	7
Open loop voltage gain GV	Guaranteed by design; TJ = 25 °C; VCC = 12 V	typ 100 dB	7
High input voltage	Synchronization function; TJ = 25 °C; VCC = 12 V	min 2 · max 3.3 V	7
Low input voltage	Synchronization function; TJ = 25 °C; VCC = 12 V	max 1 V	7
Slave sink current	VSYNCH = 2.9 V; TJ = 25 °C; VCC = 12 V	typ 0.7 · max 0.9 mA	7
Master output amplitude	ISOURCE = 4.5 mA; TJ = 25 °C; VCC = 12 V	min 2 V	7
Output pulse width	SYNCH floating; TJ = 25 °C; VCC = 12 V	typ 110 ns	7
Input pulse width	Synchronization function; TJ = 25 °C; VCC = 12 V	min 70 ns	7
Thermal shutdown TSHDN	VCC = 12 V	typ 150 °C	7
Hysteresis TSHDN	Thermal shutdown; VCC = 12 V	typ 30 °C	7

Pins, by the datasheet

1 OUT: Regulator output. · p. 4
2 SYNCH: Master/slave synchronization; outputs a half-period shifted signal when floating, or synchronizes to a higher-frequency external signal. · p. 4
3 EN: Active-high enable; ON above 1.2 V and OFF below 0.3 V. · p. 4
4 COMP: Error amplifier output for loop frequency compensation. · p. 4
5 FB: Feedback input; connect directly to the output for 0.6 V regulation, or use an external resistor divider for higher output voltages. · p. 4
6 FSW: Connect a resistor to ground to increase switching frequency; leave floating for 250 kHz operation. · p. 4
7 GND: Ground. · p. 4
8 VCC: Unregulated DC input voltage. · p. 4

Ordering codes, by the datasheet

L7981A: HSOP8 · Tube · p. 41
L7981TR: VFQFPN8 · Tape and reel · p. 41
L7981ATR: HSOP8 · Tape and reel · p. 41

Parameters

Current Limit: 4.2A
Features: Cycle-by-cycle current limiting
Frequency - Switching: 250kHz
Function: Step-down type
Junction Temperature(Max): 150℃
Number of Outputs: 1
Operating Temperature: -40℃~+150℃@(TJ)
Output Current: 3A
Output Type: Adjustable
Output Voltage: 600mV~28V
Quiescent Current: 2.4mA
Reference Voltage: 600mV
Standby Current: 20uA
Switch tube (built-in/external): Built-in
Synchronous Rectifier: No
Thermal Resistance(Junction to Ambient): 60℃/W
Topology: Buck
Voltage - Supply: 4.5V~28V
Voltage - Supply(Absolute Max): 30V

Order codes

L7981TRLCSC C2071852

Pinout

The pins of the L7981
Pin	Name	Type
1	OUT	Unspecified
2	SYNCH	Unspecified
3	EN	Unspecified
4	COMP	Unspecified
5	FB	Unspecified
6	FSW	Unspecified
7	GND	Unspecified
8	VCC	Unspecified
9	EP	Unspecified

Show this part on your page

A live frame, for any web page

<iframe src="https://pcbkit.io/embed/parts/st/L7981" title="L7981 in PCBKit" width="100%" height="480" style="border:0;border-radius:12px" allow="fullscreen" loading="lazy"></iframe>

A picture

<img src="https://pcbkit.io/embed/parts/st/L7981.jpg" alt="L7981" width="1200" height="900">

A picture that opens the part, for a README

[![L7981](https://pcbkit.io/embed/parts/st/L7981.jpg?size=s)](https://pcbkit.io/parts/st/L7981)

Questions

Is there a KiCad symbol and footprint for the L7981?

Yes. The symbol is EasyEDA_Cloud:L7980TR and the footprint EasyEDA_Cloud:VFQFPN-8_L3.0-W3.0-P0.50-TL-EP, both drawn on this page. PCBKit places them on a board for you when you design with it.

What package is the L7981?

VFQFPN-8(3x3), with 9 pins. Its footprint is drawn on this page.

Where is the L7981 datasheet?

STMicroelectronics publishes it: the Datasheet link on this page opens it.

Where can I order the L7981?

JLCPCB lists it as part C2071852, with 5 in stock; the sellers' links on this page open their listings.