TPS65950A2ZXN Datasheet, PDF (56/171 Pages) Texas Instruments – Integrated Power Management/Audio Codec

TPS65950
SWCS032E – OCTOBER 2008 – REVISED JANUARY 2011
4.3 Power Control
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4.3.1 Backup Battery Charger
If the backup battery is rechargeable, it can be recharged from the main battery. A programmable voltage
regulator powered by the main battery allows recharging of the backup battery. The backup battery charge
must be enabled using a control bit register. Recharging starts when two conditions are met:
• Main battery voltage > backup battery voltage
• Main battery > 3.2 V
The comparators of the backup battery system (BBS) give the two thresholds of the backup battery charge
startup. The programmed voltage for the charger gives the end-of-charge threshold. The programmed
current for the charger gives the charge current.
Overcharging is prevented by measurement of the backup battery voltage through the GP ADC.
Table 4-19 lists the characteristics of the backup battery charger.
Table 4-19. Backup Battery Charger Characteristics
Parameter
VBACKUP-to-MADC input attenuation
Backup battery charging current
End backup battery charging voltage:
VBBCHGEND
Test Conditions
VBACKUP from 1.8 to 3.3 V
VBACKUP = 2.8 V, BBCHEN = 1, BBISEL = 00
VBACKUP = 2.8 V, BBCHEN = 1, BBISEL = 01
VBACKUP = 2.8 V, BBCHEN = 1, BBISEL = 10
VBACKUP = 2.8 V, BBCHEN = 1, BBISEL = 11
VBACKUP = 0 V, BBCHEN = 1, BBISEL = 00
VBACKUP = 0 V, BBCHEN = 1, BBISEL = 01
VBACKUP = 0 V, BBCHEN = 1, BBISEL = 10
VBACKUP = 0 V, BBCHEN = 1, BBISEL = 11
I_VBACKUP = –10 μA, BBSEL = 00
I_VBACKUP = –10 μA, BBSEL = 01
I_VBACKUP = –10 μA, BBSEL = 10
I_VBACKUP = –10 μA, BBSEL = 11
Min Typ Max Unit
0.33
V/V
10
25
45 μA
105 150 270 μA
350 500 900 μA
0.7
1 1.8 mA
17.5
25
45 μA
105 150 270 μA
350 500 900 μA
0.7
1 1.8 mA
2.4 2.5 2.6 V
2.9 3.0 3.1 V
3.0 3.1 3.2 V
3.1 3.2 3.3 V
4.3.2 Battery Monitoring and Threshold Detection
4.3.2.1 Power On/Power Off and Backup Conditions
Table 4-20 lists the threshold levels of the battery.
Table 4-20. Battery Threshold Levels
Parameter
Test Conditions
Main battery charged threshold
VMBCH
Measured on VBAT terminal
Main battery low threshold VMBLO
VBACKUP = 3.2 V, measured on VBAT terminal (monitored
on terminal ONNOFF)
Main battery high threshold VMBHI
Measured on terminal VBAT, VBACKUP = 0 V
Measured on terminal VBAT, VBACKUP = 3.2 V
Batteries not present threshold VBNPR Measured on terminal VBACKUP with VBAT < 2.1 V
Measured on terminal VBAT with VBACKUP = 0 V
(monitored on terminal VRRTC)
Min Typ Max Unit
3.1 3.2 3.3 V
2.55 2.7 2.85 V
2.5 2.65 2.95 V
2.5 2.85 2.95
1.6 1.8 2.0 V
1.95 2.1 2.25
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Power Module
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