PRELIMINARY
FUNCTIONAL DESCRIPTION
INTRODUCTION
EXTERNAL INTERFACES
The ML2731 has 3 logic inputs: PAEN, NEGEN and PDN.
These control lines are used to select the mode of
operation to be either SLEEP, STANDBY, PRETX or
TRANSMIT. (See Table 1)
DESCRIPTION OF OPERATION
Voltage Regulator
ML2731
The ML2731 integrates two low noise voltage regulators.
The first regulator internally powers the crystal oscillator
support circuit, negative voltage generator support circuit
and other on chip circuits.
The second regulator output (REGO) powers external
circuits. (See Figure 1) It has a nominal voltage output of
2.9V and sources up to 50mA of current. The low noise
output of this regulator makes it suitable for supplying
voltage to sensitive components such as final frequency
VCO’s. The regulator output is disabled in the SLEEP mode
and is enabled in all other modes.
2.92
PDN
1
0
0
0
NEGEN
X
1
0
0
PAEN
X
X
1
0
Mode
SLEEP
STANDBY
PRETX
TRANSMIT
2.90
VOLTAGE (V)
Table 1. Circuit Enable Logic
2.88
MODE CONTROL
Mode Functions
The function of the ML2731 in each mode of operation:
SLEEP
All the circuits are disabled. Current drain is typically less
than 1mA.
STANDBY
Oscillator circuits, sine and square wave outputs and 3.0V
voltage regulator output are all enabled. VPA output is
disabled as well as all other circuits.
PRETX
Oscillator circuits, sine and square wave outputs, 3.0V
voltage regulator output, and negative voltage generator
are enabled. VBIAS is set to –3.0V. VPA output is disabled
and PA bias control loop is inactive.
TRANSMIT
Crystal oscillator circuits, sine and square wave outputs,
3.0V voltage regulator, negative voltage generator, and
VPA output are enabled, and VBIAS is voltage controlled
so that the VPA current is proportional to the ICON input
voltage.
2.86
2.84
0
10
20
30
40
50
CURRENT (mA)
Figure 1. Regulator Ouput Voltage vs. Load Current (REGO)
6
PRELIMINARY DATASHEET
January, 2000
MICRO-LINEAR [ MICRO LINEAR CORPORATION ]
