PRELIMINARY
FUNCTIONAL DESCRIPTION
OPERATION MODES AND CONTROL INTERFACE
DESCRIPTION
The signals FEEN and PAON determine the mode of
operation. The three standard modes of operation are
STANDBY, TRANSMIT, and RECEIVE. The control logic is
shown in Table 1.
STANDBY: All circuits are off (LNA bias off), PIN driver
outputs are Tri-stated.
TRANSMIT: PA and the PIN diode drivers are enabled.
The LNA is off (zero current).
RECEIVE: The LNA bias circuits and the PIN diode drivers
are enabled, PA is disabled.
In addition to the two mode control inputs, FEEN and
PAON, there is an analog voltage input that can be used
to set the power output of the amplifier. The voltage range
ML2751
required to set the output power level can be controlled
by an external resistor.
Note that the ML2751 has an internal power amplifier
ramp-on and ramp-off circuit. The power amplifier turn
on/off relative to the ramp is shown in Figure 3. The ramp-
on starts when the PA is enabled, the ramp-off starts when
it is disabled.
Two outputs, PIN and PINB, are provided from the
ML2751 to drive the external PIN diodes in the Transmit/
Receive switch. The timing for these voltage outputs is
shown in Figure 3 relative to the control pins FEEN and
PAON.
STANDBY
TRANSMIT
RECEIVE
STANDBY
FEEN
PAON
3µs
PA RF
Envelope
3µs
PIN
Tri-state
PINB
Tri-state
Figure 3. Signals vs. Mode Relationships
FEEN
0
1
1
PAON
X
0
1
Mode
STANDBY
RECEIVE
TRANSMIT
PIN
Tri-state
VCC/-10mA
VCC/+10mA
Table 1. Control Logic
PINB
Tri-state
VCC/+10mA
VCC/-10mA
LNA
Off
On
Off
PA
Off
Off
On
January, 2000
PRELIMINARY DATASHEET
7
MICRO-LINEAR [ MICRO LINEAR CORPORATION ]
