RT9503A View Datasheet(PDF) - Richtek Technology
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RT9503A Datasheet PDF : 15 Pages
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RT9503A
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 resistor. The protection threshold is
set to 6.5V, but ACIN input voltage over 18V still leads the
RT9503A 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 RT9503A continuously monitors battery temperature
by measuring the voltage between the TS and GND pins.
The RT9503A has an internal current source to provide
the bias for the most common 10kΩ negative-temperature
coefficient thermal resistor (NTC) (see Figure 4). The
RT9503A 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 charging. The RT9503A stops
charging and keeps monitoring the battery temperature
when the temperature-sense 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 via the negative-temperature coefficient
thermal resistor or by adding two external resistors. (see
Figure 5.)
The capacitor should be placed close to TS (Pin 11) and
connected to the ground plane. The capacitance value
(0.1μF to 10μF) should be selected according to the quality
of PCB layout. It is recommended to use 10μF if the layout
is poor for noise prevention.
A
ITS
Temperature
TS
Sense
VBATT
NTC
Battery
0.1µF to 10µF
VTS = ITS ×RNTC
Turn off when VTS ≥ 2.5V or VTS ≤ 0.5V
Figure 4. Temperature Sensing Configuration
A
ITS
Temperature
Sense
TS
0.1µF to 10µF
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 ISETA pin is used to determine the ACIN charge rate
from 100mA to 1A. The charge current can be calculated
as following equation.
ICHG _ AC
=
KSET
VSET
RSETA
The parameter KSET = 300 ; VSET = 2.5V. RSETA is the
resistor connected between ISETA and GND.
DS9503A-01 April 2011
www.richtek.com
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