AD7294 Analog Devices, AD7294 Datasheet - Page 44

• Manufacturer Part Number: AD7294
• Description: 12-Bit Monitor and Control System with Multichannel ADC, DACs, Temperature Sensor, and Current Sense
• Manufacturer: Analog Devices

Specifications of AD7294

• Resolution (bits): 12bit
• # Chan: 9
• Sample Rate: 200kSPS
• Interface: I²C/Ser 2-Wire,Ser
• Analog Input Type: Diff-Uni,SE-Uni
• Ain Range: (Vref) p-p,2 V p-p,Uni (Vref),Uni (Vref) x 2
• Adc Architecture: SAR
• Pkg Type: CSP

AD7294
GAIN CONTROL OF POWER AMPLIFIER
In gain control mode, a setpoint voltage, proportional in dB to
the desired output power, is applied to a power detector such as
the AD8362. A sample of the output power from the power
amplifier (PA), through a directional coupler and attenuator (or
by other means), is fed to the input of the AD8362. The VOUT
is connected to the gain control terminal of the PA, see Figure 60.
Based on the defined relationship between VOUT and the RF
input signal, the
is now an error amplifier output) until the level at the RF input
corresponds to the applied VSET. The
AD8362
adjusts the voltage on VOUT (VOUT
DIRECTIONAL
AD7294
ENVELOPE OF
TRANSMITTED
SIGNAL
COUPLER
completes a
1nF
ATTENUATOR
C5
1:4
Figure 60. Setpoint Controller Operation
T2
Rev. H | Page 44 of 48
0.1nF
0.1nF
C7
C6
AMPLIFIER
INHI
INLO
POWER
C
LPF
AD8362
VOUT
VSET
feedback loop that tracks the output of the AD8362 and adjusts
the VSET input of the
VOUT of the
the power amplifier. For this output power control loop to be
stable, a ground referenced capacitor must be connected to the
CLPF pin. This capacitor integrates the error signal (which is
actually a current) that is present when the loop is not balanced.
In a system where a variable gain amplifier (VGA) or variable
voltage attenuator (VVA) feeds the power amp, only one
is required. In such a case, the gain on one of the parts (VVA,
PA) is fixed and V
RF IN
AD8362
V
V
AD7294
IN
OUT
OUT
feeds the control input of the other.
AD8362
is applied to the gain control terminal of
accordingly.
Data Sheet
AD8362