AD5781
Data Sheet
Rev. D | Page 8 of 28
PIN CONFIGURATION AND FUNCTION DESCRIPTION
1
2
3
4
5
6
7
8
9
10
VOUT
VREFPS
VREFPF
CLR
RESET
VDD
INV
IOVCC
VCC
LDAC
20
19
18
17
16
15
14
13
12
11
AGND
VSS
VREFNS
SYNC
DGND
VREFNF
SDO
SDIN
SCLK
RFB
AD5781
TOP VIEW
(Not to Scale)
09092-
005
Figure 4. Pin Configuration
Table 6. Pin Function Descriptions
Pin No.
Mnemonic
Description
1
INV
Connection to Inverting Input of External Amplifier. See t
he AD5781 Features section for further details.
2
VOUT
Analog Output Voltage.
3
VREFPS
Positive Reference Sense Voltage Input. A voltage range of 5 V to VDD 2.5 V can be connected. A unity gain amplifier
must be connected at this pin, in conjunction with the VREFPF pin. See the AD5781 Features section for further details. 4
VREFPF
Positive Reference Force Voltage Input. A voltage range of 5 V to VDD 2.5 V can be connected. A unity gain amplifier
must be connected at these pin, in conjunction with the VREFPS pin. See AD5781 Features section for further details. 5
VDD
Positive Analog Supply Connection. A voltage range of 7.5 V to 16.5 V can be connected. VDD should be decoupled to
AGND.
6
RESET
Active Low Reset Logic Input Pin. Asserting this pin returns the AD5781 to its power-on status.
7
CLR
Active Low Clear Logic Input Pin. Asserting this pin sets the DAC register to a user defined value (s
ee Table 13) and
updates the DAC output. The output value depends on the DAC register coding that is being used, either binary or twos
complement.
8
LDAC
Active Low Load DAC Logic Input Pin. This is used to update the DAC register and, consequently, the analog output.
When tied permanently low, the output is updated on the rising edge of SYNC. If LDAC is held high during the write
cycle, the input register is updated, but the output update is held off until the falling edge of LDAC. The LDAC pin
should not be left unconnected.
9
VCC
Digital Supply Connection. A voltage in the range of 2.7 V to 5.5 V can be connected. VCC should be decoupled to DGND.
10
IOVCC
Digital Interface Supply Pin. Digital threshold levels are referenced to the voltage applied to this pin. A voltage range of
1.71 V to 5.5 V can be connected. IOVCC should not be allowed to exceed VCC.
11
SDO
Serial Data Output Pin. Data is clocked out on the rising edge of the serial clock input.
12
SDIN
Serial Data Input Pin. This device has a 24-bit shift register. Data is clocked into the register on the falling edge of the
serial clock input.
13
SCLK
Serial Clock Input. Data is clocked into the input shift register on the falling edge of the serial clock input. Data can be
transferred at clock rates of up to 35 MHz.
14
SYNC
Active Low Digital Interface Synchronization Input Pin. This is the frame synchronization signal for the input data. When
SYNC is low, it enables the input shift register, and data is then transferred in on the falling edges of the following clocks.
The input shift register is updated on the rising edge of SYNC.
15
DGND
Ground Reference Pin for Digital Circuitry.
16
VREFNF
Negative Reference Force Voltage Input. A voltage range of VSS + 2.5 V to 0 V can be connected. A unity gain amplifier
must be connected at this pin, in conjunction with the VREFNS pin. See the AD5781 Features section for further details. 17
VREFNS
Negative Reference Sense Voltage Input. A voltage range of VSS + 2.5 V to 0 V can be connected. A unity gain amplifier
must be connected at these pin, in conjunction with the VREFNF pin. See the AD5781 Features section for further details. 18
VSS
Negative Analog Supply Connection. A voltage range of 16.5 V to 2.5 V can be connected. VSS should be decoupled to
AGND.
19
AGND
Ground Reference Pin for Analog Circuitry.
20
RFB