Fairchild Semiconductor KA3504 Datasheet

KA3504

PC SMPS Super visory IC

www.fairchildsemi.com

Features

• PC Power Supply Output Moni to r Cir cui tr y

• Few External Components

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

• Over Current Protection for 3.3V/5V/12V Output With Delay Time

• Fault Protection Output With Open Collector Output

• Power Supply on/off Delay Time Control (PSON)

• Power Good Signal Gener ator With Hysteresis

• Open Collector PG Output

• 300ms Power Good Delay

• Current Sense Setting Function With RI

• Latch Function Controlled by PSON and Protection Input

• 16-Pin Dual In-line Package

FPO (Fault Protection Output)

Fault Protection Output indicates the fault condition as protection signal. When fault state occurs, the main power is to be turned-off and the PGO signal goes LOW. NORMAL = "LOW", FAULT = "HIGH"

PGO (Power Good Output)

Power Good Signal Generator is to monitor the voltage level of power supply for safe operation of a microprocessor having some delay time at turn-on. The delay time is prorammed by a timing capacitor connected to TPG pin of KA3504. The power good out put should be low state before the output voltage is out of regulation at turn-off. NORMAL = "HIGH", FAULT = "LOW"

Description

The KA3504 is complete output supervisory circuitry intended for use in the secondary side of the switched mode power supply. It provides all the functions necessary to monitor and control the output of the power supply system. Power good signal generator, Remote on and off control, some precision protection features against over-voltage and over-current are implemented. It directly senses all the output rails for OVP without any external dividers. As for output control, power good output (PGO) and Fault Protection output (FPO) are also included. Utilizing a minimum number of ext ern al co mp onents, the KA3504 offers a simple and cost effective solution, greatly reducing PCB board space for power supply system.

OCP (Over Current Protection)

It has precision OCP functions for +3.3V, +5V, +12V outputs. The block is mad e up of three comparators with current source setting function. Two inputs of each OCP comparator are connected to both sides of output inductor that is located in the secondary output of SMPS.

OVP (Over Voltage Protection)

It has OVP functions for +3.3V, +5V, +12V outputs. The circuit is made up of a comparator with three detecting inputs.

Remote ON/OFF

Remote on/off section is used to control SMPS externally. If a high signal is supplied to the remote on/off input, FPO signal becomes a high state and all secondary outputs are grounded. The remote on/off signal is transferred with some on-delay and off-delay time of 8ms, 24ms respectively with

0.1µF external capacitor.

16-DIP

Rev. 1.0.1

KA3504

Internal Block Diagram

VS12

VS5

VS33

IS12

IS5

IS33

2 1

Iref*5

(100uA)

COMP1

Iref*5

(100uA)

COMP2

Iref*5

(100uA)

COMP3

OVP

Detector

Vref

PROT

VBG=1.26V

=20uA

CHG(PROT)

COMP4

1.8V

0.6V

COMP5

1.4V

PSON T

Internal

Bias

On/Off

Delay

Control

PSON

Vref

S R

Vcc

5 Start Up

Bandgap

Reference

Iref=20uA

COMP6

1.8V

0.6V

PGIFPORI

Vref

COMP7

1.25V

GND T

CHG(PG)

1013 7 8

=15uA

COMP8

1.8V

0.6V

PGO

Absolute Maximum Ratings

Parameter Symbol Value Unit

Supply Voltage V

Input Voltage Vinput 30 V FPO Voltage V FPO Maximum Current I

FPO

Operating Temperature Topr -20 ~ +85 °C Storage Temperature Range Tstg -65 ~ +150 °C Power Dissipation P

15 ~ 30 V

30 V 20 mA

Pin Assignments : KA3504

KA3504

VS33

VS5

VS12

PGI

Vcc

FPO

PSON

1 16

0 4

IS33

IS5

IS12

TPROT

GND

PGO

KA3504

Pin Definitions

Pin No. Name Pin Function Description

1VS33

Over Voltage Protection Input for the 3.3V. It Directly Senses the 3.3V Rail Without any External Divider.

2VS5

3VS12

4PGI

Over Voltage Protection Input for the 5V. It Directly Senses the 5V Rail Without any External Divider.

Over Voltage Protection Input for the 12V. It Directly Senses the 12V Rail Without any External Divider.

Power Good Signal Generator Input. It Should be Supplied From a Bulk Dependent Voltage in Order to Detect Power on and off State.

Supply Voltage. Its Recommended Operating Voltage is Ranged from 15V to 30V.

Fault Protection Output (Open Collector Output). This Pin Indicates the Fault

6FPO

Condition. When Fault State Occurs, the PGO Signal Goes Low. Normal = ’Low", Fault = "High".

Remote on/off Input. It does TTL Operation and its Threshold Voltage is 1.4V. In

7PSON

Case of Open Circuit, the Voltage at this Pin is High (5.0V). If PSON = "Low", then FPO = "Low". It Means the Main SMPS is Working. When PSO N = "High or Open", then FPO = "High" and the main SMPS Stops to Work.

Timing pin for PSON Delay. Ton/Toff=8ms/24ms (Typ.) with Cpson=0.1µF

PSON

Externally . PSON On Delay T ime (Ton) is Measured as PSON Input Goes Low to High. PSON Off Delay Time (Toff) can be Measured Reversely.

Power Good Output Signal (Open Collector).

9PGO

PGO = "High" means "Power Good" for Operation and PGO = "Low" Means "Power Fail".

Timing pin for PGO delay. TPG = 270ms (Typ.) with CPG = 2.2µF Externally . The

10 T

High/low Threshold Voltages are 1.8V/0.6V and the Voltage of pin10 Would be Charged up to 2.9V for Noise Margin.

11 RI

12 GND

13 T

14 IS12

15 IS5

16 IS33

PROT

OCP Current Sense Setting pin. The Reference Vol tage at this pin is set to 1.25V Internally.You can fix the OCP Reference Current by Using RI Resistor.

Ground Timing pin for Under Voltage Protection and Over Current Protection Blank-out

time. Its Threshold Voltage is 1.8V and Clamped at 2.9V After full Charging. Target of Delay Time is 38ms and it is Realized Through External Capacitor (C=0.47µF).

Current Sense Input for +12V. This pin is Connected to the Current Sensing Resistor or Inductor. You can Define OCP Offset Voltage for +12V by Using RI Resistor Externally. If you Connected RI Resistor of 62kΩ at Pin11 to Ground, the Reference Current(Iref) Should be 20µA. After that, you can Make a Constant OCP Offset Voltage (V In Case the Voltage Drop (=I

O.12

OFFSET

× R

= R

× 5 × Iref).

) of the Sense Resistor or Inductor is

Larger than Offset Voltage, FPO Becomes "High" After Some Delay time and the Main SMPS is Turned-off. So the Over Current level is Determined by Following Equation. (I

O.12

= V

OFFSET

/ RS)

∗ See Application Note for Details. Current Sense Input for +5V. You can Make the +5V OCP Function as Previous

Method in IS12 (Pin14). Current Sense Input for +3.3V. You can also Make the +3.3V OCP Function as

Previous Method in IS12 (Pin14).

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