73M1866B-IMR/F Maxim Integrated Products, 73M1866B-IMR/F Datasheet - Page 57

• Manufacturer Part Number: 73M1866B-IMR/F
• Description: MICRODAA SGL PCM HIGHWAY 42-QFN
• Manufacturer: Maxim Integrated Products
• Series: MicroDAA™r

Specifications of 73M1866B-IMR/F

• Includes: PCM Highway
• Function: Data Access Arrangement (DAA)
• Interface: PCM, Serial, SPI
• Number Of Circuits: 1
• Voltage - Supply: 3 V ~ 3.6 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 42-VFQFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Supply: -
• Power (watts): -

DS_1x66B_001
8.8.1 Transmit and Receive Level Control
Refer to Section 8.5 for information about 73M1x66B levels.
8.8.1.1 Transmit Gain Scaling
The first gain stage in the transmit signal path is the digital gain whose value is controlled by writing to
Register 0x08 (TXDG). The second gain stages are the analog gains that are controlled by Register
0x14[7] (TXBST) and Register 0x14[6:5] (DAA). As a general rule to prevent clipping of the analog gain
stages, it is important to choose a value of the digital gain such that the transmit data after multiplied by
TXDG does not exceed +1.25 dBm. So for correct use of the gain controls the appropriate mix of digital
and analog settings must be used. Generally speaking, for best S/N performance, it is advisable to make
the digital words, after digital gain scaling, as large as possible without going over the +1.25 dBm limit.
Example:
Table 34 lists transmit level analog gain adjustment settings based upon the values of TXBST and DAA.
Table 35 shows a recommended gain settings for various transmit levels. With 0 dBm of Tx Data and
default setting of DAA1:0 = 01, Txbst=0, TXDG=00h, the transmit level is slightly off at –0.25 dBm.
TXDG=00000010 is required to achieve 0 dBm transmit level. For Tx level > 6 dBm, Tx Data is assumed
less than 0 dBm such that the product of Tx Data and TXDG is less than 1.25 dBm.
Rev. 1.6
If +2 dBm transmit level is desired for the case where the maximum input is 0 dBm:
Set analog gain to +3 dB (i.e. TXBST and DAA = 0) add attenuation of –1 dB by setting TXDG to
01101100 (-6 + 3.5 + 1 + 0.5 = -1); therefore, +3 - 1 = +2. Note in this case any digital gain could
cause clipping at high input levels in the analog circuitry.
TX Level
dBm
-26
-25
-24
-23
-22
-21
-20
-19
-18
TxBst DAA1 DAA0 dB
0
0
0
0
0
0
0
0
0
0x14[7]
TXBST
Table 35: Recommended Gain Setting
Analog Gain
0
0
0
0
1
1
1
1
Table 34: Transmit Gain Control
1
1
1
1
1
1
1
1
1
0x14[6]
DAA1
1
1
1
1
1
1
1
1
1
0
0
1
1
0
0
1
1
-8
-8
-8
-8
-8
-8
-8
-8
-8
0x14[5]
DAA0
1100_0010
1100_1010
1101_0010
1101_1010
1110_0110
1110_1110
1000_0010
1000_1010
1001_0010
0
1
0
1
0
1
0
1
TXDG
Digital Gain
Nom. (dB)
Gain,
+3.0
+6.0
+6.0
+2.0
-4.0
-8.0
-2.0
0.0
73M1866B/73M1966B Data Sheet
-17.75
-16.75
-15.75
-14.75
-13.75
-12.75
-11.75
-10.75
-9.75
dB
Ana+Dig
-25.75
-24.75
-23.75
-22.75
-21.75
-20.75
-19.75
-18.75
-17.75
dB
57