
Analog Integrated Circuit Device Data
Freescale Semiconductor
35
PC34708
Functional Block Requirements and Behaviors
Battery Management Block Description and Application Information
Trickle must auto recover from fault states when the fault no longer exists. The only exception is when the precharge timer has
expired (CHRTIMEEXP), then the trickle charge should stop and the CHRGLEDR should flash.
When charging from a USB source, the mini-USB will automatically detect which charger is attached and will set the buck current
limit. If the mini-USB detects that a standard USB host is attached, it will set the USB buck input current limit USBCHRG[1:0] to
100 mA. The charger will transition from trickle1 to trickle 2 at the VBAT_TRKL[1:0] setpoint, as long as the MBATT FET is not
detected. If the MBATT FET is detected, then the trickle2 mode is not allowed, and the charger will charge at the trickle1 current
up to 3.4 V. If a standard USB host is detected and the TRICKLESEL pin is not grounded, the buck will turn on, but the USBCHRG
will limit the input current to 100 mA, to stay within the USB specification. Once the system boots up, it can negotiate for the
With the AUXWEAKEN bit set high, the charger will always go into current regulation mode. When trickle charging from an aux
path, the charger will always go into input current regulation mode. When transitioned from ITRICKLE1 to ITRICKE2, the state
machine will ensure that the VAUX voltage is between the VAUXTH and VAUXWEAK thresholds. If it is, ITRICKLE2 will be
maintained. If VAUX drops below the VAUXWEAK threshold, the trickle charger will decrease to the trickle1 setpoint. If an MBATT
FET is detected, trickle2 is not allowed and the state machine will continue trickle charging at the trickle1 setting.
With AUXWEAKEN set low, the input current regulation mode is disabled. The input current limit can be set manually as
The SPI bits VBAT_TRKL[1:0] set the trickle 1 to trickle 2 transition threshold, where the trickle current changes from trickle 1 to
the trickle 2 current set by the TRICKLESEL pin. This is only valid in configurations where the MBATT FET is not detected. In
applications where the MBATT FET is present, the battery will continue to charge at the 70 mA rate until the battery reaches 3.4 V.
In the case of a dedicated charger, the trickle2 to constant current charge mode is based on the LOWBATT setpoint. When the
battery transitions from L to H (3.1 V, 3.2 V, 3.3 V, or 3.4 V), the buck charger will turn on and go into constant current mode.
Should the battery transition below the H to L threshold (3.0 V, 3.1 V, 3.2 V, or 3.3 V), the charger will revert to the trickle 2 charge
setpoint.
Table 23. Trickle Charger Settings
Parameter
BATT
Internal Trickle Charger
IRESUSITATION
BATT<1.5 V
12 mA (linear)
ITRICKLE1
1.5 V<BATT <VBAT_TRKL
70 mA (linear)
ITRICKLE2
VBAT_TRKL <BATT<LOWBATT
Programmable via TRICKLESEL
Table 24. Tricke2 Charger Current
TRICKLESEL pin
Trickle Charger Current (mA)
Mode
Ground
70 (linear)
Trickle1
VCOREDIG
325 (buck mode)
Trickle2
Floating
550 (buck mode)
Trickle2
Table 25. VBAT_TRKL Voltage Setpoint (Dedicated charger)
VBAT_TRKL
Trickle1 to Trickle2 Voltage Threshold (V)
00
2.8
01
2.9
10
3.0 (default)
11
3.1