AD5737 Analog Devices, AD5737 Datasheet - Page 38

• Manufacturer Part Number: AD5737
• Description: Quad Channel, 12-Bit, Serial Input, 4-20mA Output DAC with Dynamic Power Control and HART Connectivity
• Manufacturer: Analog Devices

Specifications of AD5737

• Resolution (bits): 12bit
• Dac Settling Time: 15µs
• Max Pos Supply (v): +33V
• Single-supply: No
• Dac Type: Current Out
• Dac Input Format: Ser,SPI

AD5737
Using Slew Rate Control
Using slew rate control can greatly reduce the current require-
ments of the AV
When using slew rate control, it is important to remember that
the output cannot slew faster than the dc-to-dc converter. The
dc-to-dc converter slews slowest at higher currents through
large loads (for example, 1 kΩ). The slew rate is also dependent
on the configuration of the dc-to-dc converter. Two examples of
the dc-to-dc converter output slew are shown in Figure 58 and
Figure 59. (V
dc-to-dc converter.)
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
Figure 60. AI
0
0
0mA TO 24mA RANGE
1kΩ LOAD
f
INDUCTOR = 10µH (XAL4040-103)
T
SW
A
AI
I
V
= 25°C
OUT
BOOST
BOOST
= 410kHz
1
CC
CC
CC
Current vs. Time for 24 mA Step Through 1 kΩ Load
corresponds to the output voltage of the
supply, as shown in Figure 60.
2
with Slew Rate Control
TIME (ms)
3
AV
5.0V
CC
DAC A
SW
4
A
GNDSW
DAC CHANNEL A
(LEFT FLOATING)
A
5
Figure 61. Configuration of Channel A Using IGATEx
6
32
28
24
20
16
12
8
4
0
R2
R1
Rev. A | Page 38 of 44
V
BOOST_A
(V
BOOST_A
EXTERNAL PMOS MODE
The
per channel, as shown in Figure 61. This mode can be used to
limit the on-chip power dissipation of the AD5737, although this
mode does not reduce the power dissipation of the total system.
The IGATEx functionality is not typically required when using
the dynamic power control feature; therefore, Figure 61 shows
the configuration of the device for a fixed V
In this configuration, the SW
pin is grounded. The V
supply of 7.4 V and a maximum supply of 33 V. This supply can
be sized according to the maximum load required to be driven.
The IGATEx functionality works by holding the gate of the
external PMOS transistor at (V
the majority of the channel’s power dissipation takes place in
the external PMOS transistor.
The external PMOS transistor should be selected to tolerate a
V
the power dissipation required. The external PMOS transistor
typically has minimal effect on the current output performance.
DS
– 5V)
voltage of at least the V
AD5737
R3
I
IGATEA
R
CHARTA
OUT_A
SET_A
can also be used with an external PMOS transistor
CURRENT OUTPUT
R
LOAD
BOOST_x
BOOST_x
x
pin is left floating, and the GNDSW
pin is connected to a minimum
BOOST_x
voltage, as well as to handle
− 5 V). This means that
BOOST_x
Data Sheet
supply.
x