Weltrend Semiconductor, Inc.
WT7520
PC POWER SUPPLY PWM SUPERVISOR
Data Sheet
REV. 0.9
February 21, 2005
The information in this document is subject to change without notice. ©Weltrend Semiconductor, Inc. All Rights Reserved.
24 2
2F, No. 24, Industry E. 9th RD., Science-Based Industrial Park, Hsin-Chu, Taiwan TEL:886-3-5780241 FAX:886-3-5794278.5770419 Email:support@weltrend.com.tw
WT7520
Data Sheet Rev. 0.90
GENERAL DESCRIPTION
The WT7520 is a pulse–width modulation (PWM) control circuit with complete protection circuits for used in the SMPS (Switched Mode Power Supply). It contains various functions, which are Over Voltage Protection, Under Voltage Protection, Power Good Output (PGO), Remote On/Off control and etc. It can minimize external components of switching power supply systems in personal computer.
Over Voltage Protection (OVP) monitors 3.3V, 5V, 12V and PT input voltage level. Under Voltage Protection (UVP) monitors 3.3V, 5V and 12V input voltage level. Power Good Output monitors the voltage level of power supply.
FEATURES
∙Complete PWM Control and Protection Circuitry
∙Over Voltage Protection for 3.3V / 5V / 12V / PT
∙Under Voltage Protection for 3.3V / 5V / 12V
∙280ms PG Time Delay
∙Power Good Output is Open Drain Output
∙PWM Control Output are Open Drain Output
∙280 mS Time Delay for UVP
∙Remote ON/OFF function De–bounce Time
∙Soft-Start function built-in
∙16–Pin Dual In–line Package
PIN CONFIGURATION
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7520 |
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V33 |
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1 |
16 |
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VADJ |
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V5 |
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2 |
15 |
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OPNEGIN |
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V12 |
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3 |
14 |
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OPOUT |
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PT |
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4 |
13 |
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VCC |
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GND |
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5 |
12 |
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DET |
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RT |
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6 |
11 |
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PG |
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C1 |
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7 |
10 |
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SS |
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C2 |
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8 |
9 |
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REM |
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Ordering Number |
Package Type |
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WT7520 |
DIP 16 |
Weltrend Semiconductor, Inc.
Page 2
WT7520
Data Sheet Rev. 0.90
PIN DESCRIPTION
Pin No. |
Pin Name |
TYPE |
FUNCTION |
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1 |
V33 |
I |
OVP/UVP input FOR 3.3V. |
2 |
V5 |
I |
OVP/UVP input for 5V. |
3 |
V12 |
I |
OVP/UVP input for 12V. |
4 |
PT |
I |
Extra OVP protection input. |
5 |
GND |
P |
Ground. |
6 |
RT |
O |
Oscillation frequency set by external resistor. |
7 |
C1 |
O |
PWM open drain output 1. |
8 |
C2 |
O |
PWM open drain output 2. |
9 |
REM |
I |
Remote on/off input. |
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REM=”low” that means the main SMPS is turned-on. |
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REM=”high”, the main SMPS is turned-off. |
10 |
SS |
O |
Soft start function set by external capacitor. |
11 |
PG |
O |
Power good signal. |
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PG= ”high” means “power good”. |
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PG= ”low” means “power fail”. |
12 |
DET |
I |
Extra protection input. |
13 |
VCC |
P |
Supply voltage. |
14 |
OPOUT |
O |
OP compensation output. |
15 |
OPNEGIN |
I |
OP compensation negative input. |
16 |
VADJ |
I |
OP compensation positive input , feedback voltage sense input. |
*The difference between WT7905 and WT7520
ITEM |
WT7905 |
WT7520 |
Pin-6 |
CT; external capacitor |
RT; external resistor |
(PWM frequency) |
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(ex. 120kΩ) |
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Pin-10 |
TPG; external capacitor |
SS; external capacitor |
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(PG delay-time function) |
(Soft-start function) |
OVP-3.3V,5V,12V |
100us (Typ.) |
510us (Typ.) |
UVP-3.3V,5V,12V |
100us (Typ.) |
110us (Typ.) |
Soft-Start function |
Set by internal circuit |
Set by external capacitor |
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(Pin-10:SS) |
Pin-4 |
PT default 0.8V (with internal |
PT default 0.8V. (with internal |
(PT) |
voltage divided resistors) |
voltage divided resistors) |
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(24K+4.6K) |
Weltrend Semiconductor, Inc.
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