Datasheet
VREF COOL WARM
COOL W ARM
VREF VREF
WARM COOL
WARM COOL
1 1
V RTH RTH
V V
RT2 =
V V
RTH 1 RTH 1
V V
æ ö
´ ´ ´ -
ç ÷
è ø
æ ö
æ ö
´ - - ´ -
ç ÷
ç ÷
è ø
è ø
VREF
COOL
COOL
V
1
V
RT1 =
1 1
+
RT2 RTH
-
VREF
TS
RT2
RT1
RTH
103AT
bq24620
bq24620
www.ti.com
SLUS893A –MARCH 2010– REVISED OCTOBER 2011
(5)
(6)
Figure 14. TS Resistor Network
For example, a 103AT NTC thermistor is used to monitor the battery pack temperature. Select T
COOL
= 0ºC,
T
WARM
= 60ºC. From the calculation and selecting a standard 5% resistor value, we can get RT1 = 2.2 kΩ, RT2 =
6.8 kΩ, and T
COLD
is –17ºC (target –20ºC); T
HOT
is 77ºC (target 75ºC), and T
CUT-OFF
is 86ºC (target 80ºC). A
small RC filter is suggested to protect the TS pin from system-level ESD.
Timer Fault Recovery
The bq24620 provides a recovery method to deal with timer fault conditions. The following summarizes this
method:
Condition 1: The battery voltage is above the recharge threshold and a time-out fault occurs.
Recovery Method: The timer fault clears when the battery voltage falls below the recharge threshold, and
battery detection begins. Taking CE low, or a POR condition, also clears the fault.
Condition 2: The battery voltage is below the RECHARGE threshold and a time-out fault occurs.
Recovery Method: Under this scenario, the bq24620 applies the IFAULT current to the battery. This small
current is used to detect a battery removal condition and remains on as long as the battery voltage stays below
the recharge threshold. If the battery voltage goes above the recharge threshold, the bq24620 disables the fault
current and executes the recovery method described in Condition 1. Taking CE low, or a POR condition, also
clears the fault.
PG Output
The open-drain PG (power good) indicates whether the VCC voltage is valid or not. The open-drain FET turns on
whenever the bq24620 has a valid VCC input (not in UVLO or ACOV or SLEEP mode). The PG pin can be used
to drive an LED or communicate with the host processor.
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