RT9515 View Datasheet(PDF) - Richtek Technology
Part Name
Description
Manufacturer
RT9515 Datasheet PDF : 11 Pages
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RT9515
Application Information
Automatically Power Source Selection
The RT9515 is a battery charger IC which is designed for
Li-ion Battery with 4.21V rated voltage.
ACIN Mode : When the ACIN input voltage is higher than
the UVP voltage level (3V) and lower than OVP voltage
level (6.5V), the RT9515 will turn on ACIN P-MOSFET.
Sleep Mode : The RT9515 will enter Sleep Mode when
ACIN input voltage are removed. This feature provides low
leakage current from the battery during the absence of
input supply.
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. 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 oltage condition is removed (ACIN < 6V), the
comparator re-enables the output by running through the
soft-start.
Battery Temperature Monitoring
The RT9515 continuously monitors battery temperature
by measuring the voltage between the TS and GND pins.
The RT9515 has an internal current source to provide the
bias for the most common 10kΩ negative-temperature
coefficient thermal resistor (NTC) (see Figure 1). The
RT9515 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 RT9515 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 2.)
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 to prevent noise.
A
ITS
Temperature
TS
Sense
VBATT
NTC
Battery
0.1uF to 10uF
VTS = ITS ×RNTC
Turn off when VTS ≥ 2.5V or VTS ≤ 0.5V
Figure 1. 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 2. Temperature Sensing Circuit
Fast-Charge Current Setting
The RT9515 offers ISETA pin to determine the ACIN charge
current from 100mA to 1.2A. The charge current can be
calculated as following equation.
ICHG_F
=
K
VISETA
RSET
www.richtek.com
8
DS9515-01 April 2011
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