BQ24070_14 Datasheet, PDF (13/33 Pages) Texas Instruments – System Power-Path Management IC

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bq24070, bq24071
SLUS694G – MARCH 2006 – REVISED DECEMBER 2014
Feature Description (continued)
further. Once the output load current exceeds the input current, the battery has to supplement the excess current
and the output voltage falls just below the battery voltage by the dropout voltage of the battery FET. This is the
battery supplement mode. When the output load current is reduced, the operation described is reversed as
shown. If the DPPM-OUT voltage was set below the battery voltage, during input current limiting, the output falls
directly to the battery's voltage.
Under USB operation, when the loads exceeds the programmed input current thresholds a similar pattern is
observed. If the output load exceeds the available USB current, the output instantly goes into the battery
supplement mode.
Figure 8 illustrates when a battery is inserted for power up; channel 1 (CH1) VIN = 0 V; channel 2 (CH2) V_USB =
0 V; channel 3 (CH3) V_OUT; output current, I_OUT = 0.25 A for V_OUT > 2 V; channel 4 (CH4) V_BAT = 3.5 V; C_(DPPM) =
0 pF. When there are no power sources and the battery is inserted, the output tracks the battery voltage if there
is no load (<10 mA of load) on the output, as shown. If a load is present that keeps the output more than 200 mV
below the battery, a short-circuit condition is declared. At this time, the load has to be removed to recover. A
capacitor can be placed on the DPPM pin to delay implementing the short-circuit mode and get unrestricted (not
limited) current.
Figure 9 illustrates USB boot up and power-up through USB; channel 1 (CH1) V(IN) (VAC) = 0 to 5 V; channel 2
(CH2) IN input current (0.2 A/div); Mode = Low; CE = High; ISET2 = High; V_BAT = 3.85 V; V_(DPPM) = 3.0 V (V_(DPPM)
× 1.15 < V_BAT, otherwise DPPM mode increases time duration). When a USB source is applied (if IN is not
present), the CE pin and ISET2 pin are ignored during the boot-up time and a maximum input current of 100 mA
is made available to the OUT or BAT pins. After the boot-up time, the IC implements the CE and ISET2 pins as
programmed.
8.3.2 Battery Temperature Monitoring
The bq2407x continuously monitors battery temperature by measuring the voltage between the TS and VSS
pins. An internal current source provides the bias for most-common 10 kΩ negative-temperature coefficient
thermistors (NTC) (see Figure 4). The device compares the voltage on the TS pin against the internal V_(LTF) and
V_(HTF) thresholds to determine if charging is allowed. Once a temperature outside the V_(LTF) and V_(HTF) thresholds
is detected, the device immediately suspends the charge. The device suspends charge by turning off the power
FET and holding the timer value (that is, timers are not reset). Charge is resumed when the temperature returns
to the normal range. The allowed temperature range for 103AT-type thermistor is 0°C to 45°C. However, the user
may increase the range by adding two external resistors. See Figure 5.
bq24070/1
LTF
HTF
V_LTF
V_HTF
PACK+
I_TS
PACK−
TS
12
+
NTC
BATTERY
PACK
UDG−04085
bq24070/1
LTF
HTF
V_LTF
V_HTF
PACK+
+
I_TS
PACK−
TS
12
RT1 _TEMP
NTC
BATTERY
RT2
PACK
UDG−04086
Figure 4. TS Pin Configuration
Figure 5. TS Pin Thresholds
8.3.3 Charge Status Outputs
The open-drain (OD) STAT1 and STAT2 outputs indicate various charger operations as shown in Table 1. These
status pins can be used to drive LEDs or communicate to the host processor. Note that OFF indicates the open-
drain transistor is turned off. Note that OFF assumes CE = High.
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Product Folder Links: bq24070 bq24071
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