rt9501 Richtek Technology Corporation, rt9501 Datasheet - Page 8

• Manufacturer Part Number: rt9501
• Description: Advanced Lithium-ion Linear Battery Charger
• Manufacturer: Richtek Technology Corporation

RT9501A/B
Charge status indication
The RT9501 indicates the status of the charger on the 3-
state STAT pin. The following table shows the statuses of
this pin.
Selecting an External PNP Pass-Transistor or
P-Channel MOSFET:
The RT9501 drives an external PNP transistor or
P-Channel MOSFET to control the charging current. The
specifications must be concerned are the
current rating and package power dissipation. The external
switch is performed as a linear regulator. The maximum
power loss occurs when the constant current regulation
starts at the beginning, and it can be calculated
approximately from following equation:
I
The minimum voltage drop between the sense-resistor
is 100mV, and the minimum precharge threshold voltage
is 2.8V.
The external pass device with PCB heatsinking must be
rated for the maximum power dissipation.
www.richtek.com
8
V
(SNS)
IN
function disable or sleep mode
Temperature fault or charge
In battery charging cycle
Charge cycle completed
is the constant regulation current.
R
CS
P
D(MAX)
Condition
Figure 8. For FB pin Function
V
O(REG)
STAT
= I
FB
CS
VDD
(SNS)
= 2.1 (1+
R4
×
BATT
(V
×
GND
CC
TS
DD
Q1
- 0.1V - 2.8V)
R
R
FB2
FB1
High Impedance
) V
STAT Pin
High
Low
voltage and
R
R
FB1
FB2
Battery
Selecting Input/Output Capacitor
In analog circuit applications, to place a high-frequency
decoupling capacitor nearby the controller IC between
input power source and ground is very important. A 0.1uF
ceramic is recommended. If a high ripple and noise input
power is chosen, it should have enough capacitance to
reduce the disturbance.
A 0.1uF to 1uF output capacitor is recommended to control
the output voltage and keep the output voltage ripple small
when the battery is disconnected.
DS9501A/B-08 October 2008