L7980 switching regulator Datasheet

L7980 Datasheet, PDF, Equivalent


Part Number

L7980

Description

2A step-down switching regulator

Manufacture

STMicroelectronics

Total Page 30 Pages
Datasheet
Download L7980 Datasheet


L7980
L7980
2 A step-down switching regulator
Features
2 A DC output current
4.5 V to 28 V input voltage
Output voltage adjustable from 0.6 V
250 kHz switching frequency, programmable
up to 1 MHz
Internal soft-start and enable
Low dropout operation: 100% duty cycle
Voltage feed-forward
Zero load current operation
Overcurrent and thermal protection
VFQFPN3x3-8L and HSOP8 package
Applications
Consumer:
STB, DVD, DVD recorder, car audio, LCD TV
and monitors
Industrial:
PLD, PLA, FPGA, chargers
Networking: XDSL, modems, DC-DC modules
Computer:
Optical storage, Hard disk drive, Printers,
Audio/graphic cards
LED driving
Figure 1. Application circuit
VFQFPN8 3x3
HSOP8 exposed pad
Description
The L7980 is a step down switching regulator with
2.5 A (minimum) current limited embedded power
MOSFET, so it is able to deliver up to 2 A current
to the load depending on the application
conditions.
The input voltage can range from 4.5 V to 28 V,
while the output voltage can be set starting from
0.6 V to VIN.
Requiring a minimum set of external components,
the device includes an internal 250 kHz switching
frequency oscillator that can be externally
adjusted up to 1 MHz.
The QFN and the HSOP packages with exposed
pad allow reducing the RthJA down to 60 °C/W
and 40 °C/W respectively.
December 2010
Doc ID 15181 Rev 4
1/44
www.st.com
44

L7980
Contents
Contents
L7980
1 Pin settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1 Pin connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2 Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3 Thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5 Functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
5.1 Oscillator and synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
5.2 Soft-start . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
5.3 Error amplifier and compensation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
5.4 Overcurrent protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
5.5 Enable function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
5.6 Hysteretic thermal shutdown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
6 Application informations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
6.1 Input capacitor selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
6.2 Inductor selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
6.3 Output capacitor selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
6.4 Compensation network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
6.4.1 Type III compensation network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
6.4.2 Type II compensation network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
6.5 Thermal considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
6.6 Layout considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
6.7 Application circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
7 Application ideas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
7.1 Positive buck-boost . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
7.2 Inverting buck-boost . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
2/44 Doc ID 15181 Rev 4


Features L7980 2 A step-down switching regulator Features ■ 2 A DC output current ■ 4.5 V to 28 V input voltage ■ Output voltage adjustable from 0.6 V ■ 250 kHz switching frequency, programmable u p to 1 MHz ■ Internal soft-start and enable ■ Low dropout operation: 100% duty cycle ■ Voltage feed-forward ■ Zero load current operation ■ Overcu rrent and thermal protection ■ VFQFPN 3x3-8L and HSOP8 package Applications Consumer: STB, DVD, DVD recorder, ca r audio, LCD TV and monitors ■ Indust rial: PLD, PLA, FPGA, chargers ■ Netw orking: XDSL, modems, DC-DC modules ■ Computer: Optical storage, Hard disk d rive, Printers, Audio/graphic cards ■ LED driving Figure 1. Application circ uit VFQFPN8 3x3 HSOP8 exposed pad De scription The L7980 is a step down swit ching regulator with 2.5 A (minimum) cu rrent limited embedded power MOSFET, so it is able to deliver up to 2 A curren t to the load depending on the applicat ion conditions. The input voltage can range from 4.5 V to 28 V, while the output voltage can .
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