RT4805A
V
OUT
Q3
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,
Q1
V
IN
LX
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 120C.
PGOOD is re-asserted when the device cools below
to 100C.
Q2
GND
Figure 2. Boost Converter With Bypass Mode
OCP
V
OUT
V
IN
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
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 15A 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.
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 1A. 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 (> 60S) from EN pull high to
nBYP pull high to guarantee normal automatic mode
operation.
Copyright © 2017 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS4805A-02
April 2017
www.richtek.com
5
RICHTEK [ RICHTEK TECHNOLOGY CORPORATION ]
