Fairchild Semiconductor KA3502 Datasheet

KA3502

PC SMPS Supervisory IC

www.fairchildsemi.com

Features

• Complete Housekeeping Circuit

• Few External Components

• Over Voltage Protection for 3.3V/5V/12V/Adj. Output

• Over Current Protection for 3.3V/5V/12V Output

• Open-Collector Output and Remote On/Off Function

• Remote On/Off Delay Time Control

• Precision Voltage Reference for Outputs, 5V/12V

• Uncommitment Precision Voltage Reference for +5V s

• Power Good Signal Generator with Hysteresis

• Disable Logi c of 3.3V, 5V, 12V for Complete Shutdown

Internal Block Diagram

V33

V5 V12

123 6

Descriptions

The KA3502 is complete housekeeping circui try for use in the secondary side of SMPS(Switched Mode Power Supply). It contains various functions, which are two Precision Voltage References, Over Voltage/Current Protection, Remote On/Off Control, Power Good Signal Generator, Disable Logic and etc.

20-DIP

PWM FB1 VREF1 UV

VCC

R5R1R3

Vcc

+ + + +

65mV

1.26V

Vcc

COMP2

Vcc

COMP3

Vcc

COMP4

COMP1

Tsur

IS33

IS12

Adj

IS5

2.7V

50mV

135mV

REM

Vcc

COMP5

1.4V

Vcc

COMP6

2.8V

R10

39k

Ion

Vcc

↔

0.7V

Ion+ Ioff

Trem

REFERENCE1

R11

5.4k

GND

R9 10k

R12

R13

R14

Vcc

COMP8

1.28V

COMP7

↔

1.24V

5.2V

Ichg

REFERENCE2

Topr

COMP9

↔

1.3V

R15

5.1k

9 PG

FB2

VREF2

Rev. 5.0

KA3502

Pin Assignments

V33

V12

Adj

VCC

PWM

REM

Trem

Topr

#10

K A 3 5 0 2

#20 IS33

IS5

IS12

Tsur

GND

FB1

VREF1

VREF2

FB2

UV #11

NO NAME FUNCTION NO NAME FUNCTION

1 V33 +3.3 V OUTPUT VOLTAGE 11 UV PG INPUT for Det 2 V5 +5 V OUTPUT VOLTAGE 12 FB2 FEEDBACK for REFERENCE 2 3 V12 +12 V OUTPUT VOLTAGE 13 VREF2 PRECISION REFERENCE 4 Adj ADJUSTABLE OVP INPUT 14 VREF1 PRECISION REFERENCE 5 VCC SUPPLY VOLTAGE 15 FB1 FEEDBACK for REFERENCE 1 6 PWM REMOTE ON/OFF OUTPUT 16 GND GROUND 7 REM REMOTE ON/OFF INPUT 17 Tsur OCP DELAY 8 Trem REMOTE ON/OFF DELAY 18 IS12 Current INPUT for +12V 9 PG POWER GOOD OUTPUT 19 IS5 Current INPUT for +5V

10 Topr PG DELAY 20 IS33 Current INPUT for +3.3V

Pin Description

Pin Number Pin Name Pin Function Descrition

1 V33 +3.3 V Output Voltage of SMPS Secondary side 2 V5 +5 V Output Voltage of SMPS Secondary side 3 V12 +12 V Output Voltage of SMPS Secondary side

Adjustable OVP Input. Its Threshold Voltage is 1.26 V. This pin can be used for

4ADJ

5 VCC Supply Voltage. Operating range is 15 V ~ 24 V. Vcc=18 V, Ta=25°C at test.

6PWM

7REM

8Trem

9PG

10 Topr 11 UV Under-Voltage Detect Pin. Its threshold voltage is 1.26V ± 20mV Typ.

12 FB2 Feedback for Precision Reference2. Absolute min/max current rating is 1 mA/30 mA.

13 VREF2

14 VREF1

15 FB1

16 GND Ground

17 Tsur

18 IS12

19 IS5 Current Sense Input for +5 V. The OCP Offset voltage for +5 V is 50 mV 20 IS33 Current Sense Input for +3.3 V. The OCP Offset voltage for +3.3 V is 135 mV

another protection signal.

Remote On/Off Output. This signal controls the primary power switch (PWM IC) through an Opto-coupler. Maximum current rating is 30 mA. When PW M="Low", the main SMPS is operational and If PWM="High", the main SMPS is turned-off.

Remote On/Off Input. It is TTL operation and its threshold voltage is 1.4 V. Voltage at this pin can reach normally 4.6 V, with absolutely maximum voltage, 5.25 V. If REM="Low", PWM="Low". That means the main SMPS is operational. When REM ="High", then PWM="High" and the main SMPS is turned-off.

Remote On/Off delay. Ton/Toff=8 ms/24 ms (Typ.) with Ctrem=0.1uF. Its High/Low threshold voltage is 2 V/0.7 V and the maximum voltage after full charging is about

2.8 V. So, ∆V (Chg.) = 2 V, ∆V (Dischg.) = 2.1 V Typ.

Power Good output signal. PG="High" means that the power is "Good" for operation and PG="Low" means "Power Fail".

PG Delay. Td=250 ms (Typ.) with Ctopr=2.2uF. The High/Low threshold voltage are 2 V/1.3 V and the voltage of PIN 10 is clamped at 5.2 V for Noise margin.

Precision Reference 2 input Voltage. This circuit equals to KA431 and it is designed for an Auxiliary voltage, +5 Vs. It is trimmed to ± 1.6%.

Precision Reference 1 Input Voltage. This circuit equals to KA431 and it is for corrective output voltages of +5 V/+12 V. It's trimmed to ± 1.6%.

Feedback for Precision Reference1. Absolute min/max current rating is 2 mA/30 mA because of internal connection.

Timing pin for Over Current Protection blank-out time. Its threshold voltage is 2 V and clamped at 2.7 V after full charging. Target of delay time is 20 ms~30 ms and it is realized through external R & C.

Current Sense Input for +12V. This pin is connected to the Current Sensing resistor or inductor. If the voltage drop of the resistor or inductor is larger than the fixed offset voltage ( 65 mV Typ.), PWM becomes "High" after some delay and the main SMPS is turned-off.

KA3502

Absolute Maximum Ratings

Parameter Symbol Value Unit

Supply Voltage Vcc 15 ~ 24 V UV Input Voltage Vuv 24 V Input Maximum Voltage Vin (max) Vcc - 3 V Cathode Current for FB1, 2 Ik1, 2 1 ~ 30 mA PWM Maximum Current Io (PWM) 30 mA PG Output Maximum Current Io (PG) 30 mA Power Dissipation Pd 1 W Operating Temperature Range Topr 0 ~ 70 °C Storage Temperature Range Tstg -65 ~ 150 °C

Temperature Characteristics

Parameter Symbol Value Unit

Temperature Stability for Vref1, 2 (0°C ≤ Ta ≤ 70°C)

∆Vref1, 2 17 mV

KA3502

Electrical Characteristics (Vcc = 18V, Ta = 25°°°°C)

Parameter Symbol Condition Min. Typ. Max. Unit

PROTECTION SECTION

Over Voltage Protection For 3.3 V Vovp33 Pin 7 (REM)=0V 3.8 4.0 4.2 V Over Voltage Protection For 5 V Vovp5 Pin 7 (REM)=0V 5.8 6.1 6.4 V Over Voltage Protection For 12 V Vovp12 Pin 7 (REM)=0V 13.4 14.2 15.0 V OVP Input Threshold Voltage for Adj Vadj Pin 7 (REM)=0V 1.22 1.26 1.30 V Comparator Offset Voltage for 3.3 V Vos33 Pin 7 (REM)=0V 125.5 135 144.5 mV Comparator Offset Voltage for 5 V Vos5 Pin 7 (REM)=0V 46.5 50 53.5 mV Comparator Offset Voltage for 12 V Vos12 Pin 7 (REM)=0V 60.5 65 69.5 mV OCP Delay Comparator Input

Threshold Voltage Pin 17 (Tsur) Input Clamp Voltage V17max Pin 7 (REM)=0V - 2.7 4 V

REMOTE ON/OFF SECTION

Remote On/off Input Threshold Vtg. Vth Pin 7 (REM): “L”→”H” 1 - 1.8 V Remote On/off Input Open Voltage Vih Pin 7 Open 4 - 5.25 V Remote On/off Input Low Current Iil Pin 7 (REM)=0 V 0 - -1.0 mA ON Delay Tim e Ton REM: “L”→“H”, C=0.1 uF 4 8 14 msec OFF Delay Time Toff REM: “L”→“H”, C=0.1 uF 16 24 34 msec PWM Saturation Voltage Vsat

PWM Leakage Current Ileak Pin 6 (PWM)=20 V - 0.01 1 uA

REFERENCE 1 SECTION

Reference Input Voltage 1 Vref1 IIk1=1 mA 2.46 2.50 2.54 V Line Regulation 1 Vref1 (line) 15 V<Vcc<20 V - 1 - mV/V Current Stability 1 ∆ Vref1 Ik1=1 mA to 10 mA - 5 20 mV Output Sinking Current Capability 1 Isink1 - 15 25 - mA Absolute Precision of Internal Three

Resistors Matching Coefficient of Internal Three

Resistors Temperature Stability ∆ Vref1 Ta=0 to 70°C (Note 1) - 13 17 mV Gain Bandwidth 1 GBW1 GV=1 (Note 1) - 1 - MHz

Vth (Tsur) Pin 7 (REM)=0V 1.9 2 2.1 V

Io=0.5 mA - - 1.3 V

(PWM)

Rint - - ± 15 - %

Rrate - - ± 1- %

+ 9 hidden pages