SI2457-D-FT Silicon Laboratories Inc, SI2457-D-FT Datasheet - Page 107

• Manufacturer Part Number: SI2457-D-FT
• Description: IC ISOMODEM SYSTEM-SIDE 24TSSOP
• Manufacturer: Silicon Laboratories Inc

Specifications of SI2457-D-FT

• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

U63 (DAAC2) is a bit-mapped register with bits 3:0 reserved and should be modified through a read-modify-write
operation.
Bits 15:8 (LCS) function as an 8-bit unsigned measure of off-hook loop current with a resolution of 1.1 mA/bit.
Bits 7:4 (ACT) set the ac termination the Si3010/Si3018 presents to Tip and Ring. The ac impedance setting is
dictated by the certification requirements for the country in which the modem is used.
U65 (DAAC4) is a bit-mapped register with bits 3:0, 12:5, and 15 reserved. Bits 1:0 and 6:5 must not be changed.
Bit 14 (PWMG) = 0 (default) provides 0 dB gain to AOUT. PWMG = 1 provides a 6 dB gain to AOUT.
Bit 13 (PDN) = 0 enables the device for normal operation. PDN = 1 completely powers down both the Si3018/10
and the Si24xx chips. The bit takes effect at the carriage return of the AT command setting this bit high. Once this
bit is set, the modem must be reset via the RESET pin to become active. When reset, the modem reverts to the
default settings.
Bit 4 (PDL) = 0 (default) enables the device for normal operation. PDL = 1 powers the Si3018/10 down. This is a
test mode typically used for board-level debugging, not normal modem operation.
U65 resets to 0x00E0 with a power-on or manual reset.
Bit
15
14
13
4
3
2
1
0
15:8
Bit
7:4
3:0
Reserved Read returns zero.
PWMG
Reserved
Reserved
Reserved
Name
PDN
FOH
DL
Reserved Read returns 0011.
Name
LCS
ACT
Function
PWM gain.
0 = No gain.
1 = 6 dB gain applied to AOUT.
Power Down.
0 = Normal.
1 = Power Down.
Must be set to zero.
Must be set to zero.
0 = Automatic calibration timer set to 426 ms.
1 = Automatic calibration timer set to 106 ms.
0 = Digital loopback beyond ISOcap interface.
1 = Digital loopback across ISOcap interface only.
Must be set to zero.
Off-hook loop current (1.1 mA/bit).
AC Termination Select
ACT AC Termination
0000
0011
0100
1111
Table 63. U62 Bit Map (Continued)
Real 600 
220  + (820  || 120 nF) and 220  + (820  || 115 nF)
370  + (620  || 310 nF)
Global complex impedance
Table 65. U65 Bit Map
Table 64. U63 Bit Map
Rev. 1.3
Function
AN93
107