RT9503 View Datasheet(PDF) - Richtek Technology
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RT9503 Datasheet PDF : 15 Pages
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RT9503
ACIN Over-Voltage Protection
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
RT9503 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 RT9503 continuously monitors battery temperature
by measuring the voltage between the TS and GND pins.
The RT9503 has an internal current source to provide the
bias for the most common 10kΩ negative-temperature
coefficient thermal resistor (NTC) (see Figure 4). The
RT9503 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 RT9503 stops
charge 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 5.)
The capacitor should be placed close to TS (Pin 9) and
connected to the ground plane. The capacitance value
(0.1uF to 10uF) should be selected according to the quality
of PCB layout. It is recommended to use 10uF if the layout
is poor if prevent noise.
VBATT
A
ITS
Temperature
TS
Sense
NTC
Battery
0.1uF to 10uF
VTS = ITS ×RNTC
Turn off when VTS ≥ 2.5V or VTS ≤ 0.5V
Figure 4. Temperature Sensing Configuration
A
ITS
Temperature
Sense
TS
0.1uF to 10uF
VBATT
RT1
RT2
NTC
Battery
VTS
=
ITS
RT2 × (RT1 + RNTC )
RT1 + RT2 + RNTC
Turn off when VTS ≥ 2.5V or VTS ≤ 0.5V
Figure 5. Temperature Sensing Circuit
Fast-Charge Current Setting
Case 1: ACIN Mode
The RT9503 offers ISETA pin to determine the ACIN charge
rate from 100mA to 1.2A. The charge current can be
calculated as following equation.
Icharge_ac
= KSET
VSET
RSETA
The parameter KSET = 300 ; VSET = 2.5V. RSETA is the
resistor connected between the ISETA and GND.
DS9503-03 April 2011
www.richtek.com
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