Regulators. L6728AH Datasheet

L6728AH Datasheet PDF

Part L6728AH
Description Single-phase Switching DC-DC Controllers & Smart Regulators
Feature www.DataSheet4U.com L6728AH High frequency single phase PWM controller with Power Good Features ■ ■.
Manufacture ST Microelectronics
Datasheet
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L6728AH
www.DataSheet4U.com
L6728AH
High frequency single phase PWM controller with Power Good
Features
Flexible power supply from 5 V to 12 V
Power conversion input as low as 1.5 V
0.8 V internal reference
0.8% output voltage accuracy
High-current integrated drivers
Power Good output
Sensorless and programmable OCP across
low-side RDS(on)
OV / UV protections
VSEN disconnection protection
Oscillator internally fixed at 600 kHz
LS-LESS to manage pre-bias start-up
Adjustable output voltage
Disable function
Internal soft-start
VFDFPN 10 package
Applications
Memory and termination supply
Subsystem power supply (MCH, IOCH, PCI)
CPU and DSP power supply
Distributed power supply
General DC / DC converters
VFQFPN 10
Description
L6728AH is a single-phase step-down controller
with integrated high-current drivers that provides
complete control logic and protection to realize in
a simple way general DC-DC converters by using
a compact VFDFPN 10 package.
Device flexibility allows managing conversions
with power input VIN as low as 1.5 V and device
supply voltage ranging from 5 V to 12 V.
L6728AH provides simple control loop with
voltage mode EA. The integrated 0.8 V reference
allows regulating output voltages with ±0.8%
accuracy over line and temperature variations.
Oscillator is internally fixed to 600 kHz.
L6728AH provides programmable dual level over
current protection as well as over and under
voltage protection. Current information is
monitored across the low-side MOSFET RDS(on)
saving the use of expensive and space-
consuming sense resistors.
PGOOD output easily provides real-time
information on output voltage status, through
VSEN dedicated output monitor.
Table 1.
Device summary
Order codes
L6728AH
L6728AHTR
Package
VFDFPN 10
Packing
Tube
Tape and reel
May 2009
Doc ID 15726 Rev 1
1/33
www.st.com
33



L6728AH
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Contents
L6728AH
1 Typical application circuit and block diagram . . . . . . . . . . . . . . . . . . . . 4
1.1 Application circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2 Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2 Pins description and connection diagrams . . . . . . . . . . . . . . . . . . . . . . 5
2.1 Pin descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.2 Thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3 Electrical specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.1 Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.2 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
4 Device description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
5 Driver section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
5.1 Power dissipation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
6 Soft-start . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
6.1 Low-side-less start up (LSLess) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
7 Over-current protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
7.1 Over-current threshold setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
8 Output voltage setting and protections . . . . . . . . . . . . . . . . . . . . . . . . 13
9 Application details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
9.1 Compensation network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
9.2 Layout guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
10 Application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
10.1 Inductor design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
10.2 Output capacitor(s) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
10.3 Input capacitors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2/33 Doc ID 15726 Rev 1




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