Datasheet

LTC1662
9
1662fa
operation
Table 1. DAC Control Functions
CONTROL
INPUT REGISTER
STATUS
DAC REGISTER
STATUS
POWER-DOWN STATUS
(SLEEP/WAKE) COMMENTSA3 A2 A1 A0
0 0 0 0 No Change No Update No Change No Operation. Power-Down Status Unchanged
(Part Stays In Wake or Sleep Mode)
0 0 0 1 Load DAC A No Update No Change Load Input Register A with Data. DAC Outputs Unchanged.
Power-Down Status Unchanged
0 0 1 0 Load DAC B No Update No Change Load Input Register B with Data. DAC Outputs Unchanged.
Power-Down Status Unchanged
1 0 0 0 No Change Update Outputs Wake Load Both DAC Regs with Existing Contents of Input Regs.
Outputs Update. Part Wakes Up
1 0 0 1 Load DAC A Update Outputs Wake Load Input Reg A. Load DAC Regs with New Contents of
Input Reg A and Existing Contents of Reg B. Outputs Update.
Part Wakes Up
1 0 1 0 Load DAC B Update Outputs Wake Load Input Reg B. Load DAC Regs with Existing Contents of
Input Reg A and New Contents of Reg B. Outputs Update.
Part Wakes Up
1 1 0 1 No Change No Update Wake Part Wakes Up. Input and DAC Regs Unchanged.
DAC Outputs Reflect Existing Contents of DAC Regs
1 1 1 0 No Change No Update Sleep Part Goes to Sleep. Input and DAC Regs Unchanged.
DAC Outputs Set to High Impedance State
1 1 1 1 Load DACs A, B
with Same
10-Bit Code
Update Outputs Wake Load Both Input Regs. Load Both DAC Regs with New
Contents of Input Regs. Outputs Update. Part Wakes Up
Note: All control codes other than those shown are undefined and not subject to test.
Transfer Function
The transfer function for the LTC1662 is:
V
OUT(IDEAL)
=
k
1024






V
REF
where k is the decimal equivalent of the binary DAC input
code D9-D0 and V
REF
is the voltage at REF (Pin 4).
Power-On Reset
The LTC1662 actively clears the outputs to zero-scale
when power is first applied, making system initialization
consistent and repeatable.
Power Supply Sequencing
The voltage at REF (Pin 4) should be kept within the range
–0.3V ≤ V
REF
≤ V
CC
+ 0.3V (see the Absolute Maximum
Ratings). Particular care should be taken during power
supply turn-on and turn-off sequences, when the voltage at
V
CC
(Pin 6) is in transition. If it is not possible to sequence
the supplies, clamp the voltage at REF by connecting a
Schottky diode between Pin 4 (anode) and Pin 6 (cathode).
Serial Interface
See Table 2. The 16-bit input word consists of the 4-bit
control code, the 10-bit input code and two don’t-care bits.
Table 2. LTC1662 Input Word
A3 A2 A1
Control Code
A0 D9 D8 D7 D6 D5 D4 D3 D2 D1 X1 X0D0
Input Code
Input Word
Don’t
Care
After the input word is loaded into the register (see Figure1),
it is internally converted from serial to parallel format. The
parallel 10-bit-wide input code data path is then buffered
by two latch registers.