CPC1560GS datasheet(8/15 Pages) LITTELFUSE

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INTEGRATED CIRCUITS DIVISION

www.ixysic.com

R04

CPC1560

2. Introduction

The CPC1560 is an optically coupled Solid State

Relay (SSR) that is self-biased from the load supply.

An optional external charge storage capacitor is used

to speed up SSR turn-on. The CPC1560 also

incorporates current limiting and a thermal shutdown

feature in the output circuitry, making the device ideal

for use in harsh conditions.

3. Functional Description

Internally, the device is composed of an LED, a

photovoltaic array with control circuitry, and two

MOSFET output switches.

Input current to the LED is the signal to turn-on the

SSR’s output MOSFET switches. The LED illuminates

the photovoltaics, which provide current to the gates of

the output MOSFETs, causing them to conduct. When

utilizing CEXT, the charge delivered to the MOSFET

gates initially includes the charge stored in the

external capacitor, causing the SSR to conduct more

quickly than if only the photovoltaic current were used.

When the Load Voltage (VL) is first applied to the

inactive outputs, the external storage capacitor begins

to charge. To ensure proper operation, the storage

capacitor should be equal to or greater than the total

gate capacitance of the two output MOSFET switches.

Charge from the load voltage is passed through

bootstrap diodes, which prevent the charge from

escaping and discharging the capacitor through the

MOSFET output switch when the SSR is turned on.

The input control current is applied, then the charge is

transferred from the storage capacitor through the

internal NPN bipolar transistor along with the charge

from the photovoltaic, to the MOSFET gates to

accomplish a rapid turn-on. After the MOSFETs have

turned on and the capacitor has discharged current

from the photovoltaic continues to flow into the gates,

keeping the MOSFETs turned on.

When the input control current is removed, gate

current from the photovoltaic stops flowing and the

PNP bipolar transistor turns on, discharging the

MOSFET gates. The MOSFETs are now off. At this

point, with load voltage applied, the capacitor begins

recharging for the next turn on cycle.

The non-conducting, optical coupling space between

the LED and the photovoltaics provides 3750Vrms of

isolation between the control input and the switched

output of the CPC1560.

Important things to note about the operation of the

CPC1560:

• The device is designed to maintain its guaranteed

operating characteristics with DC input control

current (IF) in the range of 2.5mA to 10mA (see

“Recommended Operating Conditions” on page 4). The

device will operate at input currents above and below

this range, but device operating characteristics over

the operating temperature range are not guaranteed.

• There is a minimum LED input current required for

the device to shut off: 0.1mA at 25°C (see “Electrical

Specifications” on page 5).

• The output switch will only withstand a maximum of

60 volts across its terminals before breaking down

(see“Absolute Maximum Ratings” on page 3). Maximum

voltage generally occurs when the output is off.

The CPC1560 has two different operating

configurations: unidirectional DC-only configuration,

and bidirectional AC/DC configuration.

In the unidirectional DC-only configuration, the device

switches load voltages with a fixed polarity, while in the

AC/DC configuration it can switch voltages with either

positive or negative polarities.

The advantage of operating the device in the DC-only

configuration is the ability to switch larger load

currents. The advantage of operating it in the AC/DC

configuration is the flexibility of switching load voltages

of either polarity.

4. Device Configuration

4.1 LED Resistor

To assure proper operation of the CPC1560, the LED

resistor selection should comply with the

recommended operating conditions. Although the LED

is capable of being operated up to the absolute

maximum ratings, this is not recommended. Operating

the LED beyond the recommended operating

conditions may prevent the current limit and thermal

shutdown functions from performing properly. The

equation to calculate the maximum resistor value is:

• IF_MIN = Minimum Input Control Current

• VIN_MIN = Minimum Input Power Source

• VLOW_MAX = Maximum Logic Level Low Voltage

• VF_MAX = Maximum Forward Voltage Drop of LED

• RLED_MAX = Maximum Input Resistor to LED

RLED_MAX =

VIN_MIN - VLOW_MAX - VF_MAX

IF_MIN

LOW

LED

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