LTC2630_15 Datasheet, PDF (13/22 Pages) Linear Technology – Single 12-/10-/8-Bit Rail-to- Rail DACs with 10ppm/C Reference in SC70

Timing Diagram
t₁
t₂
t₃
t₄
SCK
1
2
3
23
SDI
t₅
CS/LD
t₇
Figure 1. Serial Interface Timing
LTC2630
t₆
24
t₁₀
2630 F01
Operation
The LTC2630 is a family of single voltage output DACs in
6-lead SC70 packages. Each DAC can operate rail-to-rail
referenced to the input supply, or with its full-scale voltage
set by an integrated reference. Twelve combinations of
accuracy (12-, 10-, and 8-bit), power-on reset value (zero
or mid-scale), and full-scale voltage (2.5V or 4.096V) are
available. The LTC2630 is controlled using a 3-wire SPI/
MICROWIRE compatible interface.
Power-On Reset
The LTC2630-HZ/-LZ clear the output to zero scale when
power is first applied, making system initialization con-
sistent and repeatable.
For some applications, downstream circuits are active
during DAC power-up, and may be sensitive to nonzero
outputs from the DAC during this time. The LTC2630
contains circuitry to reduce the power-on glitch: the
analog output typically rises less than 5mV above zero
scale during power on if the power supply is ramped
to 5V in 1ms or more. In general, the glitch amplitude
decreases as the power supply ramp time is increased.
See “Power-On Reset Glitch” in the Typical Performance
Characteristics section.
The LTC2630-HM/-LM provide an alternative reset, set-
ting the output to mid-scale when power is first applied.
Transfer Function
The digital-to-analog transfer function is
V_OUT(IDEAL
)
=


k
2^N


V_REF
where k is the decimal equivalent of the binary DAC
input code, N is the resolution, and V_REF is either 2.5V
(LTC2630-L) or 4.096V (LTC2630-H) in internal refer-
ence mode, and V_CC in Supply as reference mode.
Table 1. Command Codes
Command*
C3 C2 C1 C0
0 0 0 0 Write to Input Register
0 0 0 1 Update (Power up) DAC Register
0 0 1 1 Write to and Update (Power up) DAC Register
0 1 0 0 Power down
0 1 1 0 Select Internal Reference (Power-on Reset Default)
0 1 1 1 Select Supply as Reference (V_REF = V_CC)
*Command codes not shown are reserved and should not be used.
2630ff
13