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KA3504

PC SMPS Supervisory IC

Fairchild Semiconductor 

KA3504

Pin Definitions

Pin No.

Name

1

VS33

2

VS5

3

VS12

4

PGI

5

VCC

6

FPO

7

PSON

8

TPSON

9

PGO

10

TPG

11

RI

12

GND

13

TPROT

14

IS12

15

IS5

16

IS33

Pin Function Description

Over Voltage Protection Input for the 3.3V. It Directly Senses the 3.3V Rail

Without any External Divider.

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

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

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 PSON = "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

Externally. PSON On Delay Time (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).

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

High/low Threshold Voltages are 1.8V/0.6V and the Voltage of pin10 Would be

Charged up to 2.9V for Noise Margin.

OCP Current Sense Setting pin. The Reference Voltage 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 (VOFFSET = RO × 5 × Iref).

In Case the Voltage Drop (=IO.12 × RS) 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. (IO.12 = VOFFSET/ 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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