RT9524 RICHTEK [Richtek Technology Corporation], RT9524 Datasheet - Page 8

• Manufacturer Part Number: RT9524
• Description: Linear Single Cell Li-Ion Battery Charger IC for Portable Applications
• Manufacturer: RICHTEK [Richtek Technology Corporation]

RT9524
Application Information
Description
The RT9524 is a fully integrated low cost single-cell Li-
Ion battery charger IC with a constant current mode (CC
mode) or a constant voltage mode (CV mode). The charge
current is programmable to USB100, USB500 or ISET
mode and the CV mode voltage is fixed at 4.2V. The pre-
charge threshold is fixed at 2.5V. If the battery voltage is
below the pre-charge threshold, the RT9524 charges the
battery with a trickle current until the battery voltage rises
above the pre-charge threshold. The RT9524 is capable
of being powered up from AC adapter and USB (Universal
Serial Bus) port inputs. Moreover, the RT9524 include a
linear regulator (LDO 4.9V, 50mA) for supplying low power
external circuitry.
ACIN Over Voltage Protection
The input voltage is monitored by the internal comparator
and the input over voltage protection threshold is set to
6.9V. However, input voltage over 28V will still cause
damage to the RT9524. When the input voltage exceeds
the threshold, the comparator outputs a logic signal to
turn off the power P-MOSFET to prevent the high input
voltage from damaging the electronics in the handheld
system. When the input over voltage condition is removed,
the comparator re-enables the output by running through
the soft-start.
Charger Enable and mode Setting
EN/SET is used to enable or disable the charger as well
as to select the charge current limit. Drive the EN pin to
low or leave it floating to enable the charger. The EN/SET
pin has a 200kΩ internal pull down resistor. So, when left
floating, the input is equivalent to logic low. Drive this pin
to high to disable the charger. After the EN/SET pin pulls
low for 50μs, the RT9524 enters the USB500 mode and
wait for the setting current signal. EN/SET can be used
to program the charge current during this cycle. The
RT9524 will change its charge current by sending different
pulse to EN/SET pin. If no signal is sent to EN/SET, the
RT9524 will remain in USB500 mode. A correct period of
time for high pulse is between 100μs and 700μs and the
period of pulse to pulse must be between 100μs and 700μs
to be properly read. Once EN/SET is held low for 1.5ms,
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the number of pulses is locked and sent to the control
logic and then the mode changes. The RT9524 needs to
be restarted to reset the charge current. Once the EN/
SET input is held high for more than 1.5ms, the RT9524
is disabled.
Battery Charge Profile
The RT9524 charges a Li-Ion battery with a constant
current (CC) or a constant voltage (CV).
The constant current is decided by the operation mode of
USB100, USB500 or ISET mode. The constant current is
set with the external resistor R
is fixed at 4.2V. If the battery voltage is below the Pre-
Charge Threshold, the RT9524 charges the battery with a
trickle current until the battery voltage rises above the
trickle charge threshold. When the battery voltage reaches
4.2V, the charger enters CV mode and regulates the
battery voltage at 4.2V to fully charge the battery without
the risk of over charging
Pulses
Table 1. Pulse Counting Map for EN/SET Interface
≥4
0
1
2
3
I
EN/SET
CHARGE
I
EN/SET
CHARGE
Charge Condition
USB500 Mode
USB100 Mode
USB100 Mode
Factory Mode
50µs
ISET Mode
50µs
100µs < t
100µs < t
Figure .1 (a)
Figure .1 (b)
USB500
USB500
High
High
ISET
1.5ms
< 700µs
< 700µs
and the constant voltage
Charge Current Limit
Charge Current Limit
Charge Current Limit
Charge Current Limit
1.5ms
DS9524-01 April 2011
MODE Control
ISET
USB100
Enabled
1.5ms
1.5ms