Upstream CATV Amplifiers
the state of the PGA and the output amplifiers. Tables 1
and 2 show the register format. Serial-interface timing is
shown in Figure 1.
Applications Information
High-Power and Low-Noise Modes
The MAX3514/MAX3516/MAX3517 have two transmit
modes, high power (HP) and low noise (LN). Each of
these modes is actuated by the high-order bit D7 of the
8-bit programming word. When D7 is a logic 1, HP
mode is enabled. When D7 is a logic 0, LN mode is
enabled.
Each of these modes is characterized by the activation
of a distinct output stage. In HP mode, the output stage
exhibits 15dB higher gain than LN mode. The lower
gain of the LN output stage allows for significantly lower
Table 1. Serial-Interface Control Word
BIT
MSB 7
6
5
4
3
2
1
LSB 0
MNEMONIC
D7
D6
D5
D4
D3
D2
D1
D0
DESCRIPTION
High-power/low-noise mode select
Gain code, bit 6
Gain code, bit 5
Gain code, bit 4
Gain code, bit 3
Gain code, bit 2
Gain code, bit 1
Gain code, bit 0
output noise and lower transmit/transmit-disable tran-
sients.
The full range of gain codes (D6–D0) may be used in
either mode. For DOCSIS applications, HP mode is rec-
ommended for output levels at or above +42dBmV
(MAX3514, D7 = 1, gain code = 87), LN mode when the
output level is below +42dBmV (MAX3514, D7 = 0, gain
code = 115).
Shutdown Mode
In normal operation, the shutdown pin (SHDN) is held
high. When SHDN is taken low, all circuits within the IC
are disabled. Only leakage currents flow in this state.
Data stored within the serial-data interface latches will
AG
BC
DE
F
D7 D6 D5 D4 D3 D2 D1 D0
A. tSENS
B. tSDAS
C. tSDAH
D. tSCLKL
E. tSCLKH
F. tSENH
G. tDATAH/tDATAL
Figure 1. Serial-Interface Timing Diagram
Table 2. Chip State Control Bits
GAIN CODE
SHDN TXEN D7 D6 D5 D4 D3 D2 D1 D0 (DECIMAL)
0 X XXXXXXXX
1 0 XXXXXXXX
1 1 1XXXXXXX
1 1 0XXXXXXX
1 1 00110000
1 1 01010000
1 1 01110011
1 1 11010111
1 1 11101110
1 1 11111101
*Typical Gain at +25°C, VCC = 5.0V
48
80
115
87
110
125
GAIN*
(DB)
-26
-10
8
9
20
28
STATES
Shutdown Mode
Transmit-Disable Mode
Transmit-Enable Mode, High Power
Transmit- Enable Mode, Low Noise
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