Analog Devices ADMV7320 User Manual page 4

UG-1597
GAIN TUNING PROCEDURE
Three different mechanisms are available to control the total gain of the transmitter (follow the gain tuning order in Table 1 to achieve the
correct gain level for optimal performance).
Table 1. Gain Tuning Summary
Gain Tuning Order Gain Reduction Range (dB)
First 0 to 10
Second 10 to 25
Third 25 to 40
VGA_VCTL12
The VGA_VCTL12 pin is tied to the VCTRL test point. To
achieve maximum gain, set the VCTRL test point to the −5 V dc
supply. To achieve a gain reduction between 0 dB and 10 dB,
adjust the VCTRL test point voltage between −5 V and −1 V
(typical minimum gain for variable gain amplifier).
VGA_VG345 and VGA_VG6
If further gain reduction is needed after conducting the first
step in the gain tuning order, lower the I
drain current levels, by adjusting VGA_VG345 and VGA_VG6
together, between −2 V and 0 V to achieve the proper gain level.
The total current consumption of I
lowered to 45 mA.
To tune VGA_VG345 and VGA_VG6 on ADMV7320-EVALZ,
use the following sequence:
1. Power down the chip by turning off the 5 V dc supply and
then turning off the −5 V dc supply.
2. The R36 potentiometer tunes VGA_VG345 and VGA_VG6.
Place an ampere meter between Pin 9 and Pin 10 on J1 to
monitor the I and I
D_VGA345
3. Power up the chip by turning on the −5 V supply and then
turning on the +5 V dc supply.
4. Adjust the R36 resistor to tune VGA_VG345 and VGA_VG6.
The total current of VGA_ID345 and VGA_ID6 must not
drop below 45 mA.
Gain Tuning
VGA_VCTRL12
VGA_VG345 and VGA_VG6
PA_VG1
and I
D_VGA345 D_VGA6
and I can be
D_VGA345 D_VGA6
current.
D_VGA6
Recommended Gain Tuning Voltage Range (V)
−5 to −1
−2 to 0
−2 to 0
PA_VG1 Tuning
If further gain reduction is needed after conducting the first
and second steps in the gain tuning order, lower the I
current level by adjusting PA_VG1 between −2 V to 0 V to
achieve the proper gain level. The current consumption of I
can be lowered to 100 mA.
To tune PA_VG1 on ADMV7320-EVALZ, use the following
sequence:
1. Power down the chip by turning off the +5 V dc supply and
then turning off the −5 V dc supply.
2. The R47 potentiometer tunes the PA_VG1 pin. Place an
ampere meter between Pin 3 and Pin 4 on J1 to monitor
the current of PA_VD1.
3. Power up the chip by turning on the −5 V dc supply and
then turning on the +5 V dc supply.
4. Adjust the R47 to tune PA_VG1. The P1_VD1 current
must not drop below 100 mA for PA1 tuning.
Rev. A | Page 4 of 8
ADMV7320-EVALZ User Guide
drain
D_PA1
D_PA1