AD7294 Analog Devices, AD7294 Datasheet - Page 43

• 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

Data Sheet
APPLICATIONS INFORMATION
The
purpose monitoring and control of current, voltage, and
temperature. With its 59.4 V maximum common-mode range,
the device is useful in industrial and automotive applications where
current sensing in the presence of a high common-mode voltage
is required. For example, the part is ideally suited for monitoring
and controlling a power amplifier in a cellular base station.
BASE STATION POWER AMPLIFIER MONITOR AND
CONTROL
The
achieve the optimal bias condition for the LDMOS transistor.
The main factors influencing the bias conditions are tempera-
ture, supply voltage, gate voltage drift, and general processing
parameters. The overall performance of a power amplifier
configuration is determined by the inherent tradeoffs required
in efficiency, gain, and linearity. The high level of integration
offered by the
dynamically control the drain bias current to maintain a constant
value over temperature and time, thus significantly improving
the overall performance of the power amplifier. The
incorporates the functionality of eight discrete components
AD7294
AD7294
POWER
POWER
RF CUTOFF
Rx
Tx
contains all the functions required for general-
is used in a power amplifier signal chain to
AD7294
T1
Rx POWER
Tx POWER
MONITOR
MONITOR
REF
REF
OVERRANGE
OVERRANGE
T2
allows the use of a single chip to
I
I
SENSE
SENSE
V
V
V
V
V
D1+
D2+
D2–
D1–
IN
IN
IN
IN
DD
2
1
0
1
2
3
*ADDITIONAL PINS OMITTED FOR CLARITY.
SET-POINT
240mV
RS1(+)
Figure 59. Typical HPA Monitor and Control Application
HIGH SIDE
CURRENT
R
SENSE
RS2(–)
RS1(–)
SENSE
AD7294
RS2(+)
Rev. H | Page 43 of 48
HIGH SIDE
CURRENT
R
SENSE
SENSE
MUX
RS2(–)
SENSOR
TEMP
bringing considerable board area savings over alternative
solutions.
The circuit in Figure 59 is a typical system connection diagram
for the AD7294. The device monitors and controls the overall
performance of two final stage amplifiers. The gain control and
phase adjustment of the driver stage are incorporated in the
application and are carried out by the two available uncommitted
outputs of the AD7294. Both high-side current senses measure
the amount of current on the respective final stage amplifiers.
The comparator outputs, I
OVERRANGE pins, are the controlling signals for switches
on the RF inputs of the LDMOS power FETs. If the high-side
current sense reads a value above a specified limit compared
with the setpoint, the RF IN signal is switched off by the
comparator.
By measuring the transmitted power (Tx) and the received
power (Rx), the device can dynamically change the drivers and
PA signal to optimize performance. This application requires a
logarithmic detector/controller, such as Analog Devices
or AD8362.
12-BIT
ADC
AD7294*
12-BIT
12-BIT
12-BIT
12-BIT
DAC
DAC
DAC
DAC
RF CHOKE
RF CHOKE
RF IN
RF IN
V
V
V
V
OUT
OUT
OUT
OUT
A
B
C
D
SENSE
CONTROL
CONTROL
FILTER
FILTER
1 OVERRANGE and I
GAIN
GAIN
LDMOS
LDMOS
RF OUT
RF OUT
AD7294
SENSE
AD8317
2