RT9527 RICHTEK [Richtek Technology Corporation], RT9527 Datasheet - Page 10

• Manufacturer Part Number: RT9527
• Description: Single Cell Li-Ion Battery Charger with Adjustable Charging Current for Portable Applications
• Manufacturer: RICHTEK [Richtek Technology Corporation]

RT9527
Application Information
The RT9527 is a fully integrated low cost single-cell Li-
ion battery charger ideal for portable applications. The
internal thermal feedback circuitry regulates the die
temperature to optimize the charge rate at all ambient
temperatures. The RT9527 features 20V maximum rating
voltages for VIN. Other features include under voltage
protection and over voltage protection for AC adapter
supply, as well as a charging time monitor.
Pre-Charge Mode
When the output voltage becomes lower than 2.8V, the
charging current reduces to 10% of the setting current to
protect the battery life time as shown below :
I
where K
Fast-Charge Mode
When the output voltage becomes higher than 3V, the
charging current will be equal to the setting current which
is determined by R
I
where K
Constant Voltage Mode
As the output voltage is near 4.2V, the charging current
will be reduced to maintain the output voltage. The charger
remains active and maintains the output voltage at 4.2V
in order to keep the battery in a full charge state.
Recharge Mode
When the chip is in charge termination mode, the charging
current goes down to zero and the battery voltage drops
to 4.1V. After a deglitch time of 100ms (typ.), the battery
begins recharging. However, when recharge happens, the
indicator CHG remains in logic high.
CHG Indicator
The CHG pin is an open-drain output. CHG will assert low
when the charger starts to charge the battery and become
high impedance when the charge termination current is
reached. The CHG signal is interfaced either with a
microprocessor GPIO or an LED for indication.
Copyright
www.richtek.com
10
CHG_P
CHG_F
= K
= K
©
CHG_P
CHG_Fx
2012 Richtek Technology Corporation. All rights reserved.
CHG_P
CHG_Fx
is the pre-charge current factor.
is the fast-charge current factor.
/ R
/ R
ISET
ISET
ISET
.
PGOOD Indicator
This open-drain output pin is used to indicate the input
voltage status. PGOOD
1. V
2. (V
3. V
It can be used to drive an LED or communicate to the
host processor. Note that “LOW” indicates the open-
drain transistor is turned on and the LED is bright.
Charge Termination
When the charge current is lower than the charge
termination current ratio (10% = I
4.1V and the time is larger than the deglitch time (25ms),
CHG transits from low to high. CHG will be
unless the power is re-toggled.
ISET Pin Short Protection
After VIN power plugs in, RT9527 will detect that ISET pin
is short to ground or not. If RISET is smaller than R
RT9527 regard that ISET pin is short to ground. Then,
RT9527 will disable charge function until VIN power reset.
If RISET is larger than R
begins charge status and ISET pin is short to ground,
thermal regulation will work to limit junction temperature
around 125°C.
Charging
Charging suspended
by thermal loop
Safety timers expired
TS fault
Charging done
Recharging after
termination
No valid input power
IN
IN
is a registered trademark of Richtek Technology Corporation.
IN
Charge State
< V
> V
− V
OVP
UVLO
BAT
) > V
OS_H
SHORT
output asserts low when
Low (for first charger cycle)
High impedance
Low (for first charger cycle)
High impedance
, RT9527 will charge. If RT9527
CHG
CHG Output
DS9527-00 May 2012
/ I
CHG_F
latched high
) for V
SHORT
BAT
>
,