NCV47722

www.onsemi.com

8

APPLICATIONS INFORMATION

Circuit Description

The NCV47722 is an integrated High Side Switch (HSS)

with output current capability up to 250 mA to output. It is

enabled with an input to the enable pin. The integrated

current sense feature provides diagnosis and system

protection functionality. The current limit of the device is

adjustable by resistor connected to CSO pin. Voltage on

CSO pin is proportional to output current. The HSS is

protected by both current limit and thermal shutdown.

Thermal shutdown occurs above 150

°C to protect the IC

during overloads and extreme ambient temperatures.

Enable Input

The enable pin is used to turn the regulator on or off. By

holding the pin down to a voltage less than 0.99 V, the output

of the regulator will be turned off. When the voltage on the

enable pin is greater than 2.31 V, the output of the regulator

will be enabled to power its output to the regulated output

voltage. The enable pin may be connected directly to the

input pin to give constant enable to the output regulator.

Setting the Output Current Limit

The output current limit can be set up to 350 mA by

1

limit control circuitry (see Figure 1).

V

R

CSO

1

RATIO

(eq. 1)

I

2.55

R

CSO

(eq. 2)

R

2.55

I

LIM

(eq. 3)

where

− output current actual value

RATIO − typical value of Output Current to CSO

Current Ratio for particular output current

range

CSO pin provides information about output current actual

value. The CSO voltage is proportional to output current

according to Equation 1.

using Equation 2 and Equation 3, respectively. Minimum

and maximum value of Output Current Limit can be

calculated according to Equations 4 and 5.

(eq. 4)

I

V

CSO_min

R

CSO_max

(eq. 5)

I

V

CSO_max

R

CSO_min

where

CSO Current Ratio from electrical

characteristics table and particular output

current range

CSO Current Ratio from electrical

characteristics table and particular output

current range

Current Limit from electrical characteristics

table

Current Limit from electrical characteristics

table

accuracy

accuracy

the design phase.

Diagnostic in OFF State

The NCV47722 contains also circuitry for OFF state

diagnostics for Short to Battery (STB) and Open Load (OL).

There are internal current source and Pull Down resistors

which provide additional cost savings for overall application

by excluding external components and their assembly cost

and saving PCB space and safe control IOs of a

Microcontroller Unit (MCU).

Simplified functional schematic and truth table is shown

in Figure 13 and related flowchart in Figure 14.