RT9502 RICHTEK [Richtek Technology Corporation], RT9502 Datasheet - Page 11

• Manufacturer Part Number: RT9502
• Description: Linear Single Cell Li-Ion Battery Charger IC with Dual Input Supply
• Manufacturer: RICHTEK [Richtek Technology Corporation]

Fast-Charge Current Setting
Case 1 : ACIN Mode
The RT9502 offers ISETA pin to determine the ACIN charge
rate from 100mA to 1.2A. The charge current can be
calculated as following equation.
The parameter K
resistor connected between the ISETA and GND.
DS9502-02 April 2011
Temperature
I
V
Turn off when V
charge_ac
TS
1200
1000
Sense
800
600
400
200
Figure 4. ACIN Mode Charge Current Setting
0
= I
0.5
Figure 3. Temperature Sensing Circuit
TS
= K
R
R
1.5
A
T2
T1
SET
I
×
TS
+ R
SET
0.1uF to 10uF
2.5
(R
TS
TS
R
T1
T2
V
= 300 ; V
≥
SETA
SET
3.5
2.5V or V
+ R
+ R
R
R
NTC
4.5
NTC
SETA
SETA
SET
)
5.5
(kΩ)
TS
(k)
R
R
T2
= 2.5V. R
T1
≤
6.5
0.5V
Battery
7.5
NTC
SETA
8.5
is the
V
BATT
9.5
Case 2 : USB Mode
When charging from a USB port, the ISETU pin can be
used to determine the charge current of 100mA or 500mA.
A low-level signal of ISETU pin sets the charge current at
100mA and a high level signal sets the charge current at
500mA.
Pre- Charge Current Setting
During a charge cycle if the battery voltage is below the
VPRECH threshold, the RT9502 applies a pre-charge
mode to the battery. This feature revives deeply discharged
cells and protects battery life. The RT9502 internal
determines the pre-charge rate as 10% of the fast-charge
current.
Battery Voltage Regulation
The RT9502 monitors the battery voltage through the BATT
pin. Once the battery voltage level closes to the VREG
threshold, the RT9502 voltage enters constant phase and
the charging current begins to taper down. When battery
voltage is over the VREG threshold, the RT9502 will stop
charge and keep to monitor the battery voltage. However,
when the battery voltage decreases 100mV below the
V
Charge Status Outputs
The open-drain CHG_S and PGOOD outputs indicate
various charger operations as shown in the following table.
These status pins can be used to drive LEDs or
communicate to the host processor. Note that ON
indicates the open-drain transistor is turned on and LED
is bright.
REG
Charge State
ACIN
USB
, it will be recharged to keep the battery voltage.
Charge
Charge done
Charge
Charge done
CHG_S
OFF
OFF
ON
ON
RT9502
www.richtek.com
PGOOD
OFF
OFF
ON
ON
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