RT4805AWSC datasheet(5/22 Pages) RICHTEK

5 / 22 page

RT4805A

is a registered trademark of Richtek Technology Corporation.

DS4805A-02

April

2017

www.richtek.com

GND

VOUT

VIN

Figure 2. Boost Converter With Bypass Mode

VOUT

VIN

Figure 3. RT4805A mode changed

Force Pass-Through Mode

When EN pulled high and nBYP pulled low. The device

is active in the Force pass-through mode. It supplies

current is approximately 15

A typ. From the battery,

the device is short circuit protected by a current limit of

4000mA.

VSEL

It is concerned the minimum output voltage at the

heavy load condition. There are two output voltage

levels (3.6V & 3.7V) in Boost mode and Bypass mode.

It can be selected by VSET, so it must not be floating.

PGOOD (Power Good)

Power good is a open-drain output. If it is 0, it stands for

fault occurred. The power good provide the information

to show the state of the system,



PGOOD pin show high when the sequence of

soft-start is completed.



Any fault cause PGOOD to be pulled low.



PGOOD low when PMOS current limit has triggered

for OR the die the temperature exceeds 120

C.

PGOOD is re-asserted when the device cools below

to 100

C.

OCP

The converter senses the current signal when the

high-side P-MOSFET turns on. As a result, the OCP is

cycle by-cycle current limitation. If the OCP occurs, the

converter holds off the next on pulse until inductor

current drops below the OCP limit.

OTP

The converter has an over-temperature protection.

When the junction temperature is higher than the

thermal shutdown rising threshold, the system will be

latched and the output voltage will no longer be

regulated until the junction temperature drops under the

falling threshold.

EN & nBYP

It is used to select mode. As the table 1 shown, there

are four device states.

If the EN pull low, and nBYP pull high/low, the

RT4805A is forced in shut-down mode and the

quiescent

is less than 1

A. It works in force

pass-through mode, if the EN set high and nBYP set

low. When EN and nBYP both pull high, the RT4805A

is normal operation and enter automatic mode. There

should be a delay time (> 60

S) from EN pull high to

nBYP pull high to guarantee normal automatic mode

operation.

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