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MAX3509_05 Datasheet, PDF (8/10 Pages) Maxim Integrated Products – Upstream CATV Amplifier
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Upstream CATV Amplifier
Power Amp Bias Cell
The power amp bias cell is used to enable and disable
bias to the output power amplifier. This is controlled by
TXEN and SHDN.
A
G
B
C
DE
F
Functional Modes
The MAX3509 has three functional modes controlled
through the serial interface or external pins (Table 2):
transmit mode, transmit-disable mode, and shutdown.
Transmit Mode
Transmit mode is the normal active mode of the
MAX3509. Drive TXEN and SHDN high, and set D7 = 1
to activate transmit mode.
Transmit-Disable Mode
When in transmit-disable mode, all analog circuitry is
shut down. This mode is activated by driving TXEN low
or setting D7 = 1 while keeping SHDN high. This mode
is typically used between bursts in TDMA systems.
Transients are controlled by the transformer balance.
Shutdown Mode
In normal operation, the shutdown pin (SHDN) is held
high. When SHDN is driven low, all circuits within the IC
are disabled. Only leakage currents flow in this mode.
Data stored within the serial-data interface latches will
be lost upon entering this mode. Current draw is
reduced to 1µA (typ) in shutdown mode.
D7
D6
D5
D4
D3 D2
D1
D0
A. tSENS
B. tSDAS
C. tSDAH
D. tSCKL
E. tSCKH
F. tSENH
G. tDATAH/tDATAL
Figure 2. Serial-Interface Timing Diagram
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
Transmit Disable
Not used
Gain Control, Bit 5
Gain Control, Bit 4
Gain Control, Bit 3
Gain Control, Bit 2
Gain Control, Bit 1
Gain Control, Bit 0
Table 2. Truth Table
SHDN TXEN D7
D6
D5
D4
D3
D2
D1
D0
GAIN CONTROL
WORD
STATE
0
X
X
X
X
X
X
X
X
X
X
Shutdown Mode
1
0
X
X
X
X
X
X
X
X
X
Transmit-Disable Mode
1
X
0
X
X
X
X
X
X
X
X
Transmit-Disable Mode
1
1
1
X
X
X
X
X
X
X
X
Transmit Mode
1
1
1
X
0
0
0
0
0
0
0
Gain = -25dB*
1
1
1
X
0
0
0
0
0
1
1
Gain = -24dB*
1
1
1
X
—
—
—
—
—
—
—
—
1
1
1
X
0
1
1
0
0
1
25
Gain = 0dB*
1
1
1
X
—
—
—
—
—
—
—
—
1
1
1
X
1
1
1
1
1
0
62
Gain = 35dB*
1
1
1
X
1
1
1
1
1
1
63
Gain = 36dB*
*Typical gain at +25°C and VCC = +9V.
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