POWER MANAGEMENT SYSTEM DEVICE
©2012 Rev. 1.0 Page17
12. Li-ion Battery Charger
RC5T7315 integrates Li-ion Battery charger, and the outline is as follows.
-There are two external power supply input pins; VCHG1 and VCH2.
-When both VCHG1 and VCHG2 pins have a proper input of voltage range;
the priority is given to VCHG1 pin input. Proper voltage range: 4.0V < V
VCHG 1(VCHG2)
< 6.3V
-The efficient power supply to the system and battery is performed by the current limit protection and the charge current
control.
-Various timers for the charge control are integrated.
-Chip temperature detection circuit is integrated, and it prevents the chip overheating due to the charge.
-Thermistor temperature monitoring circuit is integrated, and it stops charging at the detection of error temperature while
charging. Also, the temperature can be monitored by the integrated ADC (See “6-5.ADC” for details).
-The following charge modes are provided.
・VCHG1 charge: Charge while supplying power to the system. Start charging after automatically detecting the
connection of external power supply (VCHG1).
・VCHG2 charge: Has following three modes.
a) Charge while supplying power to the system.
b) Battery voltage condition at power-on is changed depending on a level of BOOTMASK external pin.
When BOOTMASK = “H”, charging is started during the power supply to the system, and continues until the
system’s power supply allowable voltage value set by VBATTH0 and VBATTH1. After that, the system turns
on.
When BOOTMASK = “L”, the system can turn on if DET1 is released ([DET1] = “H”) at the connection with an
external power.
c) In suspend state, the power is supplied from battery, and the charge operation turns OFF.
-There are pins that control the following: Trickle charge current, VCHG2 charge permission, VCHG2 current limit, power
supply permission voltage to the system, VSYS output ON/OFF, and suspend.
-The followings are monitored, and interrupt signals are generated.
VCHG1 connection detection, VCHG2 connection detection, VCHG1 overvoltage, VCHG2 overvoltage
Battery connection detection, Battery overvoltage,
Timer completion (Trickle charge, Rapid charge)
During charge, complete charge
Thermistor high temperature detection, thermistor low temperature detection
-Soft start circuit operates at the VCHG2 charge.
-LED connection pin is equipped; the external LED can be turned on。
-Maximum allowable current from VBAT pin to VSYS pin: 1.6A.
-VCHG1 and VCHG2 pin: 7V withstand (absolute maximum ratings)
(14 pages)
(118 pages)
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