RT9722 datasheet(9/14 Pages) RICHTEK

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RT9722

DS9722-00 August 2011

www.richtek.com

Application Information

The RT9722 is a high-side power switch with programmable

current limit function. The RT9722 provides active-high

(RT9722A) and active-low (RT9722B) enable input and full

protection functions make it optimized to replace complex

discrete on/off control circuitry.

Current Limit Setting

The current limit value ILIM, can be set by an external

resistor between SET and GND. Figure 3 shows the typical

current limit value under various setting resistance, RSET.

Figure 3. Current Limit vs. RSET Resistance

The accuracy of current limit set point may vary with

operating temperature and supply voltage, see “Typical

Operating Characteristics” graph for further details.

A few standard resistor values of the RSET and its typical

current limit set point with

±25% tolerance are listed in

Table 1.

Input and Output

VIN (input) is the power source connected to the internal

circuitry and the source of the MOSFET. VOUT (output) is

the drain of the MOSFET. In a typical application, current

flows through the switch from VIN to VOUT toward the load.

If VOUT is greater than VIN, current will flow from VOUT to

VIN since the MOSFET is bidirectional when on. The

RT9722 is designed to control current flowing from VIN to

VOUT. If a voltage applied to VOUT is greater than the voltage

on VIN, large currents may flow and cause damage to the

device.

Design Current Limit (mA)

RSET (kΩ)

Min

Typ

Max

4.7

1125.0

1500

1875.0

5.49

937.5

1250

1562.5

6.8

750.0

1000

1250.0

7.32

675.0

900

1125.0

8.66

600.0

800

1000.0

10.5

525.0

700

875.0

450.0

600

750.0

375.0

500

625.0

337.5

450

562.5

300.0

400

500.0

22.6

262.5

350

437.5

225.0

300

375.0

34.8

187.5

250

312.5

150.0

200

250.0

Chip Enable Input

The switch will be disabled when the EN/EN pin is in a

logic low/high condition. During this condition, the internal

circuitry and MOSFET are turned off, reducing the supply

current to 0.1

μA typically. The maximum guaranteed

voltage for a logic low at the EN pin is 0.6V. A minimum

guaranteed voltage of 1.4V at the EN pin will turn on the

RT9722 again. Floating the input may cause unpredictable

operation. EN should not be allowed to go negative with

respect to GND. The EN pin can be directly tied to VIN to

keep the part on.

Soft-Start for Hot Plug-In Applications

In order to eliminate the upstream voltage droop caused

by the large inrush current during hot-plug events, the

“soft-start” feature effectively isolates the power source

from extremely large capacitive loads.

Fault Flag

The RT9722 provides a FLG signal pin which is an

N-Channel open drain MOSFET output. This open drain

output goes low when current limit VOUT < VIN

− 1V, or the

die temperature exceeds 150

°C approximately. The FLG

Table 1. Current Limit vs. R

SET Resistance

Current Limit vs. RSET

200

400

600

800

1000

1200

1400

1600

1020

3040

5060

RSET (kΩ)

Ω)

RT9722 Datasheet(PDF) 9 Page - Richtek Technology Corporation

RT9722 Datasheet(HTML) 9 Page - Richtek Technology Corporation

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