ML2340, ML2350
1.0 FUNCTIONAL DESCRIPTION
1.1 D/A CONVERTER
The D/A converter is implemented using an array of equal
current sources that are decoded semi-linearly for the four
most significant bits to improve differential linearity and to
reduce output glitch around major carries. See Figure 4.
the D/A converter. The D/A converter output current is
then converted to a voltage output by an output buffer
and a resistive network. The matching among the
on-chip resistors preserves the gain accuracy between
these conversions.
The input voltage reference of the D/A converter is the
difference between V
and AGND. This difference
The D/A converter can be used in a multiplying mode by
modulating the reference input within the specified
REF IN
voltage is converted to a reference current using an
internal resistor to set up the appropriate current level in
V
range.
REF IN
V
CC
4I
4I
4I
2I
I
I
4-BIT
DIVIDER
DAC
DAC
OUT
OUT
Figure 4. D/A Converter Implementation
1.3.2 Bipolar Output Mode
In the bipolar mode, V
1.2 SINGLE-SUPPLY vs. DUAL-SUPPLY OPERATION
ML2340 and ML2350 can be powered from a single
supply ranging from 4.5V to 13.2V or dual supplies
ranging from ±2.25V to ±6.6V.
swings around V . The input
ZS
OUT
data is in 2’s complement binary format. Ideally, the
00000000 code results in an output voltage of V ; the
ZS
10000000 code results in an output voltage of (V – V );
ZS
ZS
FS
The internal digital and analog circuitry is powered
and the 01111111 results in an output voltage of (V
+
between V and AGND. The range of DGND is
CC
V
127/128), where V is the full scale output voltage
FS
FS
AGND - DGND - V – 4.5V with the logic thresholds
CC
determined by V
and the gain setting.
REF IN
set between 0.8V and 2.0V above DGND (standard TTL
logic level). The range of V is AGND - V - (V –
ZS
ZS
CC
1.4 OUTPUT BUFFER AND GAIN SETTING
2.25V).
The output buffer converts the D/A output current to a
1.3 UNIPOLAR AND BIPOLAR OUTPUT
VOLTAGE SWING
voltage output using a resistive network with proper gain
setting determined by the GAIN 0 and GAIN 1 inputs.
There are four possible gain settings for unipolar output
voltage mode and bipolar output voltage mode as listed
below:
ML2340 and ML2350 can operate in either unipolar or
bipolar output voltage mode. Unipolar/bipolar mode
selection is determined by comparing the zero scale
voltage (V ) of these devices to a precise internal
ZS
Unipolar Output Voltage Mode
reference that is referred to AGND. V is ideally the
ZS
voltage that will be produced at the DAC voltage output
when the digital input data is set to all “0’s” Unipolar
Voltage Output Swing
GAIN 1
GAIN 0
GAIN
Relative to VZS
mode is selected when V is lower than 1.00 volt, and
ZS
1
0
0
1
1
0
1
0
1
/4
VREF IN ¥ 1/
VREF IN ¥ 1/
4
bipolar mode is selected when V is greater than 1.50
ZS
volts.
1
/2
2
1.3.1 Unipolar Output Mode
1
2
VREF IN ¥ 1
VREF IN ¥ 2
In the unipolar mode, V
swings above V . Ideally the
ZS
OUT
00000000 code results in an output voltage of V , and
ZS
the 11111111 code results in an output voltage of
V
x 255/256, where V is the full-scale voltage
FS
FS
determined by V
and the gain setting.
REF IN
7
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