LTC2632CTS8-HZ12#TRMPBF Linear Technology, LTC2632CTS8-HZ12#TRMPBF Datasheet - Page 19

• Manufacturer Part Number: LTC2632CTS8-HZ12#TRMPBF
• Description: MS-DAC/Industrial, 12-Bit SPI Dual DAC ( 2.5LSB Max INL, 4.096V Ref, Reset To Z
• Manufacturer: Linear Technology

Specifications of LTC2632CTS8-HZ12#TRMPBF

• Input Channel Type: Serial
• Data Interface: 3-Wire, Serial
• Supply Voltage Range - Analog: 4.5V To 5.5V
• Supply Current: 500µA
• Digital Ic Case Style: TSOT-23
• No. Of Pins: 8
• Rohs Compliant: Yes
• Resolution (bits): 12bit

OPERATION
Reference Modes
For applications where an accurate external reference is not
available, nor desirable due to limited space, the LTC2632
has a user-selectable, integrated reference. The integrated
reference voltage is internally amplified by 2x to provide
the full-scale DAC output voltage range. The LTC2632-LI/
LTC2632-LX/LTC2632-LZ provides a full-scale output of
2.5V. The LTC2632-HI/LTC2632-HZ provides a full-scale
output of 4.096V. The internal reference can be useful in
applications where the supply voltage is poorly regulated.
Internal reference mode can be selected by using com-
mand 0110b, and is the power-on default for LTC2632-HZ/
LTC2632-LZ, as well as for LTC2632-HI/LTC2632-LI.
The 10ppm/°C, 1.25V (LTC2632-LI/LTC2632-LX/LTC2632-
LZ) or 2.048V (LTC2632-HI/LTC2632-HZ) internal reference
is available at the REF pin. Adding bypass capacitance
to the REF pin will improve noise performance; 0.1µF
is recommended, and up to 10µF can be driven without
oscillation. This output must be buffered when driving an
external DC load current.
Alternatively, the DAC can operate in external reference
mode using command 0111b. In this mode, an input voltage
supplied externally to the REF pin provides the reference
(1V ≤ V
external reference voltage supplied sets the full-scale DAC
output voltage. External reference mode is the power-on
default for the LTC2632-LX.
The reference mode of LTC2632-HZ/LTC2632-LZ/LTC2632-
HI/LTC2632-LI (internal reference power-on default),
can be changed by software command after power-up.
The same is true for the LTC2632-LX (external reference
power-on default).
REF
≤ V
CC
) and the supply current is reduced. The
Power-Down Mode
For power-constrained applications, power-down mode can
be used to reduce the supply current whenever less than
two DAC outputs are needed. When in power-down, the
buffer amplifiers, bias circuits, and integrated reference
circuits are disabled, and draw essentially zero current.
The DAC outputs are put into a high-impedance state, and
the output pins are passively pulled to ground through
individual 200k resistors. Input and DAC-register contents
are not disturbed during power-down.
Either channel or both channels can be put into power-
down mode by using command 0100b in combination with
the appropriate DAC address (n). The supply current is
reduced approximately 30% for each DAC powered down.
The integrated reference is automatically powered down
when external reference is selected using command 0111b.
In addition, all the DAC channels and the integrated refer-
ence together can be put into power-down mode using
power-down chip command 0101b. When the integrated
reference is in power-down mode, the REF pin becomes
high impedance (typically > 1GΩ). For all power-down
commands the 16-bit data word is ignored.
Normal operation resumes after executing any command
that includes a DAC update (as shown in Table 1). The se-
lected DAC is powered up as its voltage output is updated.
When a DAC which is in a powered-down state is powered
up and updated, normal settling is delayed. If less than
two DACs are in a powered-down state prior to the update
command, the power-up delay time is 10µs. However, if
both DACs and the integrated reference are powered down,
then the main bias generation circuit block has been auto-
matically shut down in addition to the DAC amplifiers and
reference buffers. In this case, the power up delay time is
12µs. The power-up of the integrated reference depends
on the command that powered it down. If the reference is
powered down using the select external reference com-
mand (0111b), then it can only be powered back up using
select internal reference command (0110b). However, if
the reference was powered down using power-down chip
command (0101b), then in addition to the select internal
reference command (0110b), any command that powers
up the DACs will also power-up the integrated reference.
LTC2632
19
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