max5302cuat Maxim Integrated Products, Inc., max5302cuat Datasheet - Page 6

• Manufacturer Part Number: max5302cuat
• Description: Max5302 Low-power, 12-bit Voltage-output Dac With Serial Interface
• Manufacturer: Maxim Integrated Products, Inc.

Low-Power, 12-Bit Voltage-Output DAC
with Serial Interface
_____________________Pin Description
The MAX5302 contains a voltage-output digital-to-analog
converter (DAC) that is easily addressed using a simple
3-wire serial interface. The IC includes a 16-bit shift
register, and has a double-buffered input composed of
an input register and a DAC register (see
Diagram). In addition to the voltage output, the amplifier’s
negative input is available to the user.
The DAC is an inverted R-2R ladder network that converts
a digital input (12 data bits plus 1 sub-bit) into an
equivalent analog output voltage in proportion to the
applied reference voltage. Figure 1 shows a simplified
circuit diagram of the DAC.
The reference input accepts positive DC and AC signals.
The voltage at the reference input sets the full-scale out-
put voltage for the DAC. The reference input voltage
range is 0 to (V
represented by a digitally programmable voltage
source, as expressed in the following equation:
where NB is the numeric value of the DAC’s binary
input code (0 to 4095), V
and Gain is the externally set voltage gain.
The impedance at the reference input is code dependent,
ranging from a low value of 14kΩ when the DAC has an
input code of 1554 hex, to a high value exceeding several
gigaohms (leakage currents) with an input code of
0000 hex. Because the input impedance at the reference
pin is code dependent, load regulation of the reference
source is important.
6
PIN
_______________________________________________________________________________________
1
2
3
4
5
6
7
8
V
NAME
SCLK
GND
OUT
REF
V
OUT
DIN
CS
FB
DD
DD
= (V
- 1.4V). The output voltage (V
REF
Detailed Description
DAC Output Voltage
Chip-Select Input. Active low.
Serial-Data Input
Serial-Clock Input
DAC Output Amplifier Feedback
Reference Voltage Input
Ground
Positive Power Supply
REF
· NB / 4096) Gain
is the reference voltage,
Reference Inputs
FUNCTION
Functional
OUT
) is
In shutdown mode, the MAX5302’s REF input enters a
high-impedance state with a typical input leakage current
of 0.001µA.
The reference input capacitance is also code dependent
and typically ranges from 15pF (with an input code of
all 0s) to 50pF (at full scale).
The MAX873 +2.5V reference is recommended for the
MAX5302.
The MAX5302’s DAC output is internally buffered by a
precision amplifier with a typical slew rate of 0.6V/µs.
Access to the output amplifier’s inverting input provides
the user greater flexibility in output gain setting/signal
conditioning (see the Applications Information section).
With a full-scale transition at the MAX5302 output, the
typical settling time to ±1/2LSB is 14µs when loaded
with 5kΩ in parallel with 100pF (loads less than 2kΩ
degrade performance).
The amplifier’s output dynamic responses and settling
performances are shown in the Typical Operating Char-
acteristics.
The MAX5302 features a software-programmable shut-
down that reduces supply current to a typical value of
4µA. Writing 111X XXXX XXXX XXXX as the input control
word puts the device in shutdown mode (Table 1).
In shutdown mode, the amplifier’s output and the refer-
ence input enter a high-impedance state. The serial
interface remains active. Data in the input registers is
retained in shutdown, allowing the MAX5302 to recall
the output state prior to entering shutdown. Exit shutdown
mode by either recalling the previous configuration or
Figure 1. Simplified DAC Circuit Diagram
AGND
REF
SHOWN FOR ALL 1s ON DAC
2R
2R
R
2R
R
2R
R
Output Amplifier
Shutdown Mode
2R
MSB
FB
OUT