LTC2641 Linear Technology, LTC2641 Datasheet - Page 12

• Manufacturer Part Number: LTC2641
• Description: (LTC2641 / LTC2642) 16-/14-/12-Bit VOUT DACs
• Manufacturer: Linear Technology

LTC2641/LTC2642
Power-On Reset
The LTC2641/LTC2642 include a power-on reset circuit
to ensure that the DAC ouput comes up in a known state.
When V
the output of the LTC2641 to zero-scale (code 0). The
LTC2642 powers up to midscale (bipolar zero). Depend-
ing on the DAC number of bits, the midscale code is:
Unipolar Confi guration
Figure 2 shows a typical unipolar DAC application for
the LTC2641. Tables 1a, 1b and 1c show the unipolar
binary code tables for 16-bit, 14-bit and 12-bit operation.
OPERATION
APPLICATIONS INFORMATION
12
2
3
4
5
www.DataSheet4U.com
CS
SCLK
DIN
CLR
LTC2641-16
Figure 2. 16-Bit Unipolar Output (LTC2641-16) Unipolar V
DD
5V/3V
Table 1b. 14-Bit Unipolar Binary Code Table
(LTC2641-14)
MSB
1111 1111 1111 11xx V
1000 0000 0000 00xx V
0000 0000 0000 01xx V
0000 0000 0000 00xx 0V
V
DD
BINARY NUMBER
is fi rst applied, the power-on reset circuit sets
7
DIGITAL INPUT
IN DAC LATCH
0.1μF
16-BIT DAC
V
2.5V
REF
1
REF
LSB
0.1μF
REF
REF
REF
(16,383/16,384)
(8,192/16,384) = V
(1/16,384)
GND
ANALOG OUTPUT
V
OUT
8
4.7μF
(V
26412 F02
6
OUT
)
OUT
LT
1/2 LTC6078
–
+
®
1019CS8-2.5
REF
5V/3V
GND
/2
0.1μF
IN
OUT
= 0V to V
5V
UNIPOLAR V
0V TO 2.5V
32,768 (LTC2642-16); 8,192 (LTC2642-14); or 2,048
(LTC2642-12).
Clearing the DAC
A 10ns (minimum) low pulse on the ⎯ C ⎯ L ⎯ R pin asynchro-
nously clears the DAC latch to code zero (LTC2641) or to
midscale (LTC2642).
The external amplifi er provides a unity-gain buffer. The
LTC2642 can also be used in unipolar confi guration by
tying R
clear to midscale.
REF
OUT
Table 1c. 12-Bit Unipolar Binary Code Table
(LTC2641-12)
MSB
1111 1111 1111 xxxx V
1000 0000 0000 xxxx V
0000 0000 0001 xxxx V
0000 0000 0000 xxxx 0V
FB
BINARY NUMBER
DIGITAL INPUT
IN DAC LATCH
and INV to REF. This provides power-up and
Table 1a. 16-Bit Unipolar Binary Code Table
(LTC2641-16)
MSB
1111 1111 1111 1111 V
1000 0000 0000 0000 V
0000 0000 0000 0001 V
0000 0000 0000 0000 0V
BINARY NUMBER
DIGITAL INPUT
IN DAC LATCH
LSB
REF
REF
REF
LSB
(4,095/4,096)
(2,048/4,096) = V
(1/4,096)
ANALOG OUTPUT
REF
REF
REF
(V
(65,535/65,536)
(32,768/65,536) = V
(1/65,536)
OUT
ANALOG OUTPUT
)
(V
OUT
REF
)
/2
REF
/2
26412f