AD7294BSUZRL Analog Devices Inc, AD7294BSUZRL Datasheet - Page 44

• Manufacturer Part Number: AD7294BSUZRL
• Description: IC,Data Acquisition System,4-CHANNEL,12-BIT,TQFP,64PIN,PLASTIC
• Manufacturer: Analog Devices Inc
• Type: ADC, DACr

Specifications of AD7294BSUZRL

• Resolution (bits): 12 b
• Sampling Rate (per Second): 22.22k
• Data Interface: Serial
• Voltage Supply Source: Analog and Digital
• Voltage - Supply: 4.5 V ~ 5.5 V
• Operating Temperature: -55°C ~ 150°C
• Mounting Type: Surface Mount
• Package / Case: 64-TQFP, 64-VQFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

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 AD8362 adjusts the voltage on VOUT (VOUT
is now an error amplifier output) until the level at the RF input
corresponds to the applied VSET. The AD7294 completes a
DIRECTIONAL
ENVELOPE OF
TRANSMITTED
SIGNAL
COUPLER
1nF
ATTENUATOR
C5
1:4
Figure 60. Setpoint Controller Operation
T2
Rev. F | 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 AD8362 accordingly.
VOUT of the AD8362 is applied to the gain control terminal of
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 AD8362
is required. In such a case, the gain on one of the parts (VVA,
PA) is fixed and V
RF IN
V
V
AD7294
IN
OUT
OUT
feeds the control input of the other.