Si3220/Si3225
When generating a high-voltage ringing amplitude using –24 V) rails using the switch internal to the Si3200. The
the Si3220, the power dissipated during the OHT state Si3220’s GPO pin is used along with the external
typically increases due to operating from the ringing transistor circuit to switch the V
rail (the ringing
BAT
BRING
battery supply in this mode. To reduce power, the voltage battery rail) onto the Si3200’s V
pin when
Si3220/Si3200 chipset provides the ability to ringing is enabled. The GPO signal is driven
accommodate up to three separate battery supplies by automatically by the ringing cadence provided that the
implementing a secondary battery switch using a few RRAIL bit of the RLYCON register is set to 1 (signifying
low-cost external components as illustrated in Figure that a third battery rail is present).
22. The Si3220’s BATSEL pin is used to switch between
the V
(typically –48 V) and V
(typically
BLO
BHI
Si3220
Si3225
Battery
Control
Logic
Battery
BATSEL
SVBAT
Sense
Circuit
40.2 kΩ
806 kΩ
BATSEL
Si3200
Battery
Linefeed
Circuitry
Select
Control
VBLO
VBATL
VBAT
VBATH
VBHI
Figure 19. External Battery Switching Using the Si3220/Si3225
Si3220
806 kΩ
SVBAT
Si3200
VBAT
0.1 µF
0.1 µF
R101
CXT5401
R9
40.2 kΩ
Q1
VBRING
VBLO
VBATH
VBATL
10 kΩ
BATSEL
R102
Q2
402 kΩ
R103
D1
CXT5551
IN4003
VBHI
Figure 20. 3-Battery Switching with Si3220/Si3200
Rev. 1.0
41
SILICONIMAGE [ Silicon image ]
