APW7057 Datasheet, PDF (1/14 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 Temp.
•
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
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 volt-
age mode synchronous switching controller that drives
external N-channel MOSFETs. When the input sup-
ply drops close to output, the upper MOSFET remains
on, achieving 100% duty cycle. Internal loop compen-
sation is optimized for fast transient response, elimi-
nating external compensation network. The precision
0.8V reference makes this part suitable for a wide va-
riety of low voltage applications. Soft start is internally
set to 2ms, limiting the input in-rush current and pre-
venting the output from overshoot during powering up.
The APW7057 has over current and short circuit
protections. Over current protection is achieved by
monitoring the voltage drop across the high side
MOSFET, eliminating the need for a current sens-
ing 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 condition persists, the
controller will be shut down. To restart the controller,
either recycle the V_CC supply or momentarily 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.
Pinouts
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.3 - Oct., 2003
www.anpec.com.tw