DAC8812_15 Datasheet, PDF (15/29 Pages) Texas Instruments – DAC8812 Dual, Serial-Input 16-Bit Multiplying Digital-to-Analog Converter

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CS
CLK
SDI
EN
D0
16
D1
D2
D3
D4
D5
D6
D7
D8
D9
D10
D11
D12
D13
D14
D15
A0
DAC _A
B
A1 Decode
Power-
on
Reset
Input
Register R
DAC8812
SBAS349C – AUGUST 2005 – REVISED NOVEMBER 2015
V_REF A B
DAC A
Register R
DAC A
V_DD
R_FBB
I_OUTA
A_GNDA
Input
Register R
DAC B
Register R
DAC B
Set
MSB
Set
MSB
R_FBB
I_OUTB
A_GNDB
DGND
MSB
LDAC
RS
Figure 32. System-Level Digital Interfacing
8.3.2 Power-On Reset
When the V_DD power supply is turned on, an internal reset strobe forces all the Input and DAC registers to the
zero-code state or half-scale, depending on the MSB pin voltage. The V_DD power supply should have a smooth
positive ramp without drooping, in order to have consistent results, especially in the region of V_DD = 1.5 V to
2.3 V. The DAC register data stays at zero or half-scale setting until a valid serial register data load takes place.
8.3.2.1 ESD Protection Circuits
All logic-input pins contain back-biased ESD protection zener diodes connected to ground (DGND) and V_DD as
shown in Figure 33.
V_DD
DIGITAL
INPUTS
250 W
DGND
Figure 33. Equivalent ESD Protection Circuits
8.4 Device Functional Modes
8.4.1 Serial Data Interface
The DAC8812 uses a 3-wire (CS, SDI, CLK) SPI-compatible serial data interface. Serial data of the DAC8812 is
clocked into the serial input register in an 18-bit data-word format. MSB bits are loaded first. Table 1 defines the
18 data-word bits for the DAC8812.
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