BQ25050 Datasheet, PDF (17/28 Pages) Texas Instruments – 1A, Single-Input, Single Cell Li-Ion Battery Charger with 50-mA LDO, External Power Path

bq25050
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Table 1. V_TS vs Temperature
(47kΩ Thermistor, b=4050, NCP15WB473F)
TEMPERATURE
–20°C
0°C
45°C
60°C
80°C
VTS
0.968 V
0.600 V
0.450 V
0.250 V
0.110 V
SLUSA33 – MARCH 2010
50mA LDO (LDO)
The LDO output of the bq25050 is a low dropout linear regulator (LDO) that supplies up to 50mA while regulating
to V_LDO. The LDO is active whenever the input voltage is above V_UVLO and below V_OVP. It is not affected by the
CTRL input. The LDO output is used to power circuitry such as USB transceivers in dead battery conditions. This
allows the user to operate the product immediately after plugging the adapter in, instead of waiting for the battery
to charge to useable levels.
Charge Status Indicator (CHG)
The bq25050 contains an open drain CHG output that indicates when charge cycles and faults. When charging a
battery in precharge, fastcharge or CV mode, the CHG output is pulled to VSS. Once the BAT output reaches
regulation and the charge current falls below the termination threshold, CHG goes high impedance to signal the
battery is fully charged. The CHG output goes low during battery recharge cycles to signal the host to monitor for
termination.
Additionally, CHG notifies the host if a NTC temperature fault has occurred. CHG pulses with a period of 100ms
and a 50% duty cycle if a TS faults occurs. Connect CHG to the required logic level voltage through a resistor to
use the signal with a microprocessor. The sink current I_CHG must be below 5mA.
The IC monitors the CHG pin when no input is connected to verify if the phone circuitry is active. If the voltage at
CHG is logic low when no driven low, the TS current source is turned off for a low quiescent current state. Once
the voltage at CHG increases above logic high, the current source is turned on to allow the host to sense battery
temperature.
Single Input Interface (CTRL)
CTRL is used to enable/disable the device as well as select the input current limit, enable/disable charge, extend
the TS operation range and disable V_IN-DPM mode. CTRL is pulled low to enable the device. After the deglitch
t_{CTRL_DGL} expires, the IC enters the 32ms WAIT state. CTRL may be used to program the bq25050 during this
time. Once t_WAIT expires, the IC starts up. If no command is sent to CTRL during t_WAIT, the IC starts up with a
default 285mA current limit, termination enabled and V_IN-DPM enabled.
Programming the different modes is done by pulsing the CTRL input. See Table 2 for a map of the different
modes. The width of the CTRL pulses is unimportant as long as they are between 50µs and 1000µs long. The
time between pulses must be between 50ms and 1000µs to be properly read. Once CTRL is held low for 2ms,
the number of pulses is passed to the control logic and decoded and then the mode changes. To ensure proper
operation, more than 16 pulses are not recommended. See Figure 26 for a flow diagram of the CTRL interface.
# OF PULSES
1
2
3
4
5
6
7
8
Table 2. Pulse Counting Map for CTRL Interface
BGATE CONTROL
Force Termination
Force On Disable
Force On Enable
No Change
No Change
No Change
No Change
No Change
CURRENT LIMIT
No Change
No Change
No Change
93 mA
187 mA
280 mA
374 mA
467 mA
TS RANGE
No Change
No Change
No Change
No Change
No Change
No Change
No Change
No Change
V_IN-DPM
No Change
No Change
No Change
No Change
No Change
No Change
No Change
No Change
Copyright © 2010, Texas Instruments Incorporated
Product Folder Link(s): bq25050
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