RT9511 RICHTEK [Richtek Technology Corporation], RT9511 Datasheet - Page 17

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

C
The ACIN input voltage is monitored by an internal OVP
comparator. The comparator has an accurate reference of
2.5V from the band-gap reference. The OVP threshold is
set by the internal resistive. The protection threshold is
set to 6.5V, but ACIN input voltage over 18V still leads the
RT9511 to damage. 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 (ACIN <
6V), the comparator re-enables the output by running
through the soft-start.
Battery Temperature Monitoring
The RT9511 continuously monitors battery temperature
by measuring the voltage between the TS and GND pins.
The RT9511 has an internal current source to provide the
bias for the most common 10k
coefficient thermal resistor (NTC) (see Figure 5). The
RT9511 compares the voltage on the TS pin against the
internal VTS_HIGH and VTS_LOW thresholds to determine
if charging is allowed. When the temperature outside the
VTS_HIGH and VTS_LOW thresholds is detected, the
device will immediately stop the charge. The RT9511 stops
charging and keep monitoring the battery temperature
when the temperature sense input voltage is back to the
threshold between VTS_HIGH and VTS_LOW, the charger
will be resumed. Charge is resumed when the temperature
returns to the normal range. However, the user may modify
thresholds by the negative-temperature coefficient thermal
resistor or adding two external resistors. (see Figure 6.)
The capacitor should be placed close to TS (Pin 9) and
connected to the ground plane. The capacitance value
(0.1 F to 10 F) should be selected according to the quality
of PCB layout. It is recommended to use a 10 F if the
layout is poor to prevent noise.
DS9511-01 April 2011
IN
Over Voltage Protection
negative-temperature
Temperature
Fast-Charge Current Setting
Case 1: ACIN Mode
The RT9511 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.
I
V
Turn off when V
V
Turn off when V
Sense
charge_ac
TS
TS
Temperature
Figure 5. Temperature Sensing Configuration
Sense
= I
= I
Figure 6. Temperature Sensing Circuit
TS
TS
= K
A
R
R
R
T2
T1
NTC
I
SET
A
TS
0.1µF to 10µF
+ R
SET
TS
TS
(R
TS
I
TS
R
T1
TS
T2
V
= 300 ; V
SETA
SET
2.5V or V
2.5V or V
+ R
+ R
NTC
0.1µF to 10µF
NTC
SET
)
TS
TS
R
Battery
R
T2
= 2.5V. R
T1
NTC
0.5V
0.5V
RT9511
www.richtek.com
Battery
V
NTC
BATT
SETA
is the
V
BATT
17