RT9511 RICHTEK [Richtek Technology Corporation], RT9511 Datasheet - Page 18

• Manufacturer Part Number: RT9511
• Description: Fully Integrated Battery Charger with Two Step-Down Converters
• Manufacturer: RICHTEK [Richtek Technology Corporation]

RT9511
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 the 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
V
to the battery. This feature revives deeply discharged cells
and protects battery life. The RT9511 internally determines
the pre-charge rate as 10% of the fast-charge current.
Battery Voltage Regulation
The RT9511 monitors the battery voltage through the BATT
pin. Once the battery voltage level closes to the V
threshold, the RT9511 voltage enters constant phase and
the charging current begins to taper down. When battery
voltage is over the V
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 output indicates various charger
operations as shown in the following table. These status
pin 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.
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18
PRECH
REG
1200
1000
800
600
400
200
, it will be recharged to keep the battery voltage.
Figure 7. ACIN Mode Charge Current Setting
0
threshold, the RT9511 applies a pre-charge mode
0.5
1.5
2.5
REG
3.5
threshold, the RT9511 will stop
R
R
4.5
SETA
SETA
(k )
5.5
(k)
6.5
7.5
8.5
9.5
REG
Temperature Regulation and Thermal Protection
In order to maximize the charge rate, the RT9511 features
a junction temperature regulation loop. If the power
dissipation of the IC results in a junction temperature
greater than the thermal regulation threshold (125 C), the
RT9511 throttles back on the charge current in order to
maintain a junction temperature around the thermal
regulation threshold (125 C). The RT9511 monitors the
junction temperature, T
battery from the input if T
continues until junction temperature falls below thermal
regulation threshold (125 C) by the hysteresis level. This
feature prevents the maximum power dissipation from
exceeding typical design conditions.
External Timer
As a safety mechanism, the RT9511 has a user-
programmable timer that monitors the pre-charge and fast
charge time. This timer (charge safety timer) is started at
the beginning of the pre-charge and fast charge period.
The safety charge timeout value is set by the value of an
external capacitor connected to the TMR pin (C
TMR is short to GND, the charge safety timer is disabled.
As C
T
As timer fault, re-plug-in power or pull high and re-pull low
EN can release the fault condition.
As a safety mechanism, the RT9511 has a user-
programmable timer that monitors the pre-charge and fast
charge time. This timer (charge safe timer) is started at
the beginning of the pre-charge and fast-charge period.
The safety charge timeout value is set by an external
capacitor (CT) connected between TIMER pin and GND.
The timeout fault condition can be released by resetting
the input power or the EN pin. If the TIMER is shorted to
GND, the charge safety timer will be disabled.
PRECH
ACIN
USB
TMR
Charge State
. T
= 0.1 F, T
PRECH
Charge
Charge Done
Charge
Charge Done
= C
PRECH
TMR
x 2460/0.1
J
J
, of the die and disconnects the
is ~2460 secs and T
exceeds 125 C. This operation
CHG_S
OFF
OFF
ON
ON
DS9511-01 April 2011
FAULT
TMR
), if pin
is 8 x