APW7057_08 Datasheet, PDF (1/15 Pages) Anpec Electronics Coropration – High Power Step-Down Synchronous DC/DC Controller

APW7057
High Power Step-Down Synchronous DC/DC Controller
Features
• Operates from +5V Input
• 0.8V Internal Reference Voltage
- ±1.5% Accuracy Over Line, Load and
Temperature
•
0.8V to V Output Range
CC
• Full Duty Cycle Range
- 0% to 100%
• Internal Loop Compensation
• Internal Soft-Start
- Typical 2ms
• Programmable Over-Current Protection
- Lossless Sensing Using MOSFET R_{DS (ON)}
• Under-Voltage Protection
• Drives External N-Channel MOSFETs
• Shutdown Control
• Small SOP-8 Package
• Lead Free and Green Devices Avaliable
(RoHS Compliant)
Applications
• Motherboard
• Graphics Cards
• Cable or DSL Modems, Set Top Boxes
• DSP Supplies
• Memory Supplies
• 5V Input DC-DC Regulators
• Distributed Power Supplies
General Description
The APW7057 is a 300kHz constant frequency voltage
mode synchronous switching controller that drives exter-
nal N-channel MOSFETs. When the input supply drops
close to output, the upper MOSFET remains on, achiev-
ing 100% duty cycle. Internal loop compensation is opti-
mized for fast transient response, eliminating external
compensation network. The precision 0.8V reference
makes this part suitable for a wide variety of low voltage
applications. Soft-start is internally set to 2ms, limiting
the input in-rush current and preventing the output from
overshoot during powering up.
The APW 7057 has over current and short circuit
protections. Over current protection is achieved by moni-
toring the voltage drop across the high side MOSFET,
eliminating the need for a current sensing resistor and
short circuit condition is detected through the FB pin. If
either fault conditions occur, the APW7057 would initiate
the soft-start cycle. After three cycles and if the fault condi-
tion persists, the controller will be shut down. To restart
the controller, either recycle the V_CC supply or momen-
tarily pull the OSCSET pin below 1.25V.
The APW7057 can be shutdown by pulling the OCSET
pin below 1.25V. In shutdown, both gate drive signals will
be low. The controller is available in a small SOP-8
package.
Pin Configuration
BOOT
1
UGATE
2
GND
3
LGATE
4
8
PHASE
7
OCSET
6
FB
5
VCC
SOP-8 (Top View )
ANPEC reserves the right to make changes to improve reliability or manufacturability without notice, and
advise customers to obtain the latest version of relevant information to verify before placing orders.
Copyright © ANPEC Electronics Corp.
1
Rev. A.5 - Jun., 2008
www.anpec.com.tw