BD2202G,BD2206G

Technical Note

8/12

www.rohm.com

2011.05 - Rev.B

© 2011 ROHM Co., Ltd. All rights reserved.

●

Operation description

BD2202G and BD2206G are high side switch IC with over-current protection function. The operating voltage range is from

2.7V to 3.6V and the current limit value is set on 400mA, 1A.

When an over-current condition lasts longer than an over-current shutdown time, the switch turns OFF. The OFF switch is set

on latch mode. The switch set on latch mode returns (to normal) by toggling EN pin from High to Low to High.

1.Switch On/Off control

VIN and VOUT pins are connected to each switch MOSFET drain and source. Moreover, VIN pin is also used as a power

supply input for the internal control circuit.

When the switch is turned on from EN control input, VIN and VOUT is connected by a 150mΩ switch. In normal condition,

the switch shows bidirectional. Therefore, when the voltage of VOUT is higher than VIN the current flows from VOUT to

VIN.

In the switch MOSFET, there is a parasitic diode (body diode) between drain and source. So, even when the switch is off,

when voltage of VOUT is higher than VIN, the current flows through the body diode from VOUT to VIN.

2. Over current detection (OCD)

The over current detection circuit limits current when current flowing in switch MOSFET exceeds the current limit threshold.

There are three types of response against over current. The over current detection circuit is in operation when the power

switch is ON (when EN signal is active).

2-1 When the switch is turned on while the output is in short-circuit status

When the switch is turned on while the output is in short-circuit status, the switch become current limit mode soon.

2-2 When the output short-circuits while the switch is on

When the output short-circuits or heavy load is connected while the switch is on, very large current flows until the over

current limit circuit responds. When the current detection, limit circuit works, current limitation is carried out.

2-3 When the output current increases gradually

When the output current increases gradually, current limitation does not work until the output current exceeds the over

current detection value. When it exceeds the detection value, current limitation is carried out.

3.Over current shutdown

When the over-current detection circuit detects an over-current, TBLANK timer starts working. When the over-current

condition disappears before TBLANK2 stage, TBLANK timer is reset. When the over-current condition progresses to more

than TBLANK1, the switch is shut off. The OFF switch is set on latch off mode. The latch is reset when EN terminal is

toggled or when UVLO is detected.

4.Under voltage lockout (UVLO)

UVLO keeps the power switch off until VIN voltage exceeds 2.3V (Typ.). Moreover, from a power switch ON situation, if

VIN voltage drops to 2.2V (Typ.), the power switch is set on OFF. UVLO has a 100mV hysteresis. The under voltage lock

out circuit is in operation when power switch is ON (when EN signal is active).

5.Thermal shutdown

When the chip temperature increases to 160°C (Typ.), the thermal shut down circuit works and the power switch is turned

OFF. When the chip temperature falls to 140°C (Typ.), the power switch output returns (to normal). This operation will

repeat itself until the causes of the chip temperature rise are removed or until the power switch output is turned off.

The thermal shutdown circuit is in operation when the power switch is ON (when EN signal is active).