AD7294 Datasheet, PDF (1/45 Pages) Analog Devices – 12-Bit, Multichannel, DAC/ADC Temperature Sensor and Current Sense for Monitor and Control Applications

12-Bit, Multichannel, DAC/ADC Temperature Sensor and
Current Sense for Monitor and Control Applications
Preliminary Technical Data
AD7294
FEATURES
GENERAL DESCRIPTION
4-channel 12-bit DAC
Guaranteed monotonic
10 μs settling time
10 mA sink and source capability
The AD7294 contains all the functions required for general-
purpose monitoring and control of current, voltage, and
temperature integrated into a single-chip solution. The part
Offset in for range adjustment
includes low voltage (±200 mV) analog-input sense amplifiers
Output span: 5 V in 0 to 15 V range
9-channel, 12-bit ADC
200 kSPS throughput
Input range: 0 to VREF, 0 to 2 VREF
Differential/single-ended
Limit registers per channel
for current monitoring across shunt resistors, temperature-sense
inputs, and four uncommitted analog input channels multiplexed
into a 200 kSPS SAR ADC. An internal low ppm reference is
provided to drive both the DAC and ADC. Four 12-bit DACs
provide the outputs for voltage control. The AD7294 also includes
2 high-side current sense
limit registers for alarm functions. The part is designed on a high
48 V max operation
±1% FS accuracy
±200 mV input range
voltage DMOS process for a high voltage compliance, 48 V on
the current-sense inputs, and up to 15 V DAC output voltage.
3-channel temperature sensor
Diode temperature measurement
±2°C accuracy
Measurement range: −10°C to +90°C
The part is ideal for bias current control of the power transistors
used in power amplifiers employed in CDMA, GSM, EDGE, and
UMTS cellular base stations.
Internal 2.5 V reference
I²C®-compatible serial interface
Temperature range: −40°C to +105°C
Alert function
The DACs provide digital control with 1.2 mV resolution to
control the bias currents of the power transistors. They can also
be used to provide control voltages for variable gain amplifiers
Package type: LFCSP-56, TQFP-64
or impedance match networks in the main signal chain. Thermal
APPLICATIONS
diode based temperature sensors are incorporated to compensate
for temperature effects. The ADC monitors the high-side current
Cellular base station (GSM, EDGE, UMTS, CDMA)
Point-to-multipoint and other RF transmission systems
12 V, 24 V, 48 V automotive applications
Industrial control
and temperature. All this functionality is provided in a 56-lead
LFCSP package and a 64-lead TQFP package operating over a
temperature range of −40°C to +105°C.
FUNCTIONAL BLOCK DIAGRAM
R Sense
VPP(1-2)
RS1(+) RS1(-)
RS2(+) RS2(-)
REFOUT/
REFOUT/
REFIN ADC REFIN DAC AVDD(1-5) AGND(1-9) V+(1-2)
RF CHOKE
ISENSE2
OVER-RANGE
ISENSE1
OVER-RANGE
VIN 0
VIN 1
VIN 2
VIN 3
D1 (+)
HIGH SIDE
CURRENT
SENSE
SET-POINT
240mV
HIGH SIDE
CURRENT
SENSE
MUX
2.5V
REF
12-BIT
ADC
12-BIT
DAC
100K
100K _200K
200K
12-BIT
DAC
100K
100K _200K
200K
VOUT A
FILTER
OFFSET IN A
VOUT B
FILTER
RF OUT
LDMOS
LDMOS
D0 (+)
T1
T0
D0 (-)
D1 (-)
AD7294
LIMIT
REGISTERS
TEMP
SENSOR
CONTROL
LOGIC
I2C INTERFACE
PROTOCOL
12-BIT
DAC
100K
100K _200K
200K
12-BIT
DAC
100K
100K _200K
200K
OFFSET IN B
VOUT C _GAIN
CONTROL
OFFSET IN C
VOUT D
IMPEDANCE
MATCH
OFFSET IN D
DVDD DGND(1-2) SDA SCL A2 A1 A0 CAP ALERT
Figure 1. Typical Configuration for AD7294 in Cellular Base Station RF LDMOS Power Amplifier Control
Rev. PrB
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