Datasheet

AD420 Data Sheet
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
00494-002
NC
1
V
L
L
2
F
AUL
T DETECT
3
RANGE SELECT 2
4
NC
24
V
CC
23
NC
22
CAP 2
21
RANGE SELECT 1
5
CAP
1
20
CLEAR
6
BOOST
19
LATCH
7
I
OUT
18
CLOCK
8
V
OUT
17
D
AT
A IN
9
OFFSET TRIM
16
DATA OUT
10
REF IN
15
GND
11
REF OUT
14
NC
12
NC
13
NC = NO CONNECT
AD420
TOP VIEW
(Not to Scale)
Figure 2. Pin Configuration
Table 4. Pin Function Descriptions
Pin No. Mnemonic Function
1, 12,
13, 24
NC No Connection. No internal connections inside device.
2 V
LL
Auxiliary buffered +4.5 V digital logic voltage. This pin is the internal supply voltage for the digital
circuitry and can be used as a termination for pull-up resistors. An external +5 V power supply can be
connected to V
LL
. It will override this buffered voltage, thus reducing the internal power dissipation. The
V
LL
pin should be decoupled to GND with a 0.1 µF capacitor. See the Power Supplies and Decoupling
section.
3 FAULT DETECT FAULT DETECT, connected to a pull-up resistor, is asserted low when the output current does not match
the DAC’s programmed value, for example, in case the current loop is broken.
4 RANGE SELECT 2 Selects the converter’s output operating range. One output voltage range and three
5
RANGE SELECT 1
output current ranges are available.
6 CLEAR Valid V
IH
unconditionally forces the output to go to the minimum of its programmed range. After CLEAR
is removed the DAC output will remain at this value. The data in the input register is unaffected.
7 LATCH In the 3-wire interface mode a rising edge parallel loads the serial input register data into the DAC. To
use the asynchronous mode connect LATCH through a current limiting resistor to V
CC
.
8 CLOCK Data Clock Input. The clock period is equal to the input data bit rate in the 3-wire interface mode and is
16 times the bit rate in asynchronous mode.
9 DATA IN Serial Data Input.
10 DATA OUT Serial Data Output. In the 3-wire interface mode, this output can be used for daisy-chaining multiple
AD420s. In the asynchronous mode a positive pulse will indicate a framing error after the stop-bit is
received.
11 GND Ground (Common).
14 REF OUT +5 V Reference Output.
15 REF IN Reference Input.
16 OFFSET TRIM Offset Adjust.
17 V
OUT
Voltage Output.
18 I
OUT
Current Output.
19 BOOST Connect to an external transistor to reduce the power dissipated in the AD420 output transistor, if
desired.
20
CAP 1
These pins are used for internal filtering. Connect capacitors between each of these
21 CAP 2 pins and V
CC
. Refer to the description of current output operation.
22 NC No Connection. Do not connect anything to this pin.
23 V
CC
Power Supply Input. The V
CC
pin should always be decoupled to GND with a 0.1 µF capacitor. See the
Power Supplies and Decoupling section.
Rev. I | Page 6 of 16