RT9701PBL datasheet(8/10 Pages) RICHTEK

8 / 10 page

RT9701

DS9701-13 March 2007

www.richtek.com

Application Information

The RT9701 is a high-side single N-Channel MOSFET

switch with active-high enable input.

Input and Output

VIN (input) is the power supply connection to the circuitry

and the drain of the output MOSFET. VOUT (output) is

the source of the output MOSFET. In a typical circuit,

current flows through the switch from VIN to VOUT toward

the load. Both VOUT pins must be short on the board

and connected to the load and so do both VIN pins but

connected to the power source.

Thermal Shutdown

Thermal shutdown shuts off the output MOSFET if the

die temperature exceeds 130

°C and 20°C of hysteresis

forces the switch turning off until the die temperature

drops to 110

°C.

Soft Start

In order to eliminate the upstream voltage droop caused

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

“

soft-start” feature effectively isolates power supplies

from such highly capacitive loads.

Under-voltage Lockout

UVLO prevents the MOSFET switch from turning on until

input voltage exceeds 1.8V (typical). If input voltage drops

below 1.8V (typical), UVLO shuts off the MOSFET switch.

Filtering

To limit the input voltage drop during hot-plug events,

connect a 1

μF ceramic capacitor from VIN to GND.

However, higher capacitor values will further reduce the

voltage drop at the input.

Connect a sufficient capacitor from VOUT to GND. This

capacitor helps to prevent inductive parasitics from pulling

VOUT negative during turn-off or EMI damage to other

components during the hot-detachment. It is also

necessary for meeting the USB specification during hot

plug-in operation. If RT9701 is implanted in device end

application, minimum 1

μF capacitor from VOUT to GND

is recommended and higher capacitor values are also

preferred.

Figure 1. High Side Power Switch

Figure 2. High Side Power Switch with Chip Enable

Control

RT9701CB

VIN

VOUT

GND

OUT2

OUT

OUT1

OUT

Chip Enable

RT9701CBL

VIN

VOUT

GND

OUT2

1uF

OUT

IN = 1uF, COUT = 470uF (Low ESR) on M/B

IN = 1uF, COUT = 330uF (Low ESR) on Notebook

IN = 10uF, COUT = 1uF on USB device

OUT1

OUT

Thermal

Shut

Dowm

Response

Time (50ms/Div)

CH1

CH1: VEN = 5V/Div, CH3: IOUT@RL1

Ω: 1A/Div

CH2: IOUT@short

: 1A/DiV, VIN = 5V

CH2

Thermal Shut Down

CH3

Current Limiting and Short Protection

The current limit circuit is designed to protect the system

supply, the MOSFET switch and the load from damage

caused by excessive currents. The current limit threshold

is set internally to allow a minimum of 1.1A through the

MOSFET but limits the output current to approximately

1.5A typical. When the output is short to ground, it will

limit to a constant current 1A until thermal shutdown or

short condition removed.

RT9701PBL Datasheet(PDF) 8 Page - Richtek Technology Corporation

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