AD8315ARM Analog Devices, AD8315ARM Datasheet - Page 16

• Manufacturer Part Number: AD8315ARM
• Description: Controllers, 50dB GSM PA Controller
• Manufacturer: Analog Devices

AD8315
For operation in controller mode, both jumpers, LK1 and LK2,
should be removed. The setpoint voltage is applied to V
,
SET
RFIN is connected to the RF source (PA output or directional
coupler), and V
is connected to the gain control pin of the
APC
PA. When used in controller mode, a capacitor must be installed in
C
for loop stability. For GSM/DCS handset power amplifiers,
4
this capacitor should typically range from 150 pF to 300 pF.
A quasi-measurement mode (where the AD8315 delivers an
output voltage that is proportional to the log of the input signal)
can be implemented, to establish the relationship between V
SET
and RFIN, by installing the two jumpers, LK1 and LK2. This
mimics an AGC loop. To establish the transfer function of the
log amp, the RF input should be swept while the voltage on
V
is measured, that is, the SMA connector labeled VSET
SET
now acts as an output. This is the simplest method to validate
operation of the evaluation board. When operated in this mode,
Figure 12. Layout of Component Side (MSOP)
a large capacitor (0.01 mF or greater) must be installed in C4
(filter capacitor) to ensure loop stability.
Figure 13. Silkscreen of Component Side (MSOP)
–16–
REV. B