pc87591l-n05 National Semiconductor Corporation, pc87591l-n05 Datasheet - Page 179

• Manufacturer Part Number: pc87591l-n05
• Description: Lpc Mobile Embedded Controller
• Manufacturer: National Semiconductor Corporation

Revision 1.2
4.0 Embedded Controller Modules
4.12 DIGITAL TO ANALOG CONVERTER (DAC)
The DAC converts digital input values to analog signals. The DAC support four channels for handling up to four independent
conversions in parallel.
4.12.1 Features
4.12.2 Functional Description
The DAC has four independent digital-to-analog converters. Each converter generates an output in the range of 0V to AV
with 8-bit resolution. The converters drive the four output pins DA0-3, as shown in Figure 64. An output impedance of 3 K
allows a settling time of about 1 s on a 50 pF load.
When a DAC channel is enabled, its output is defined by the value written to its DACDATn register. DACDAT0-3 control
DA0-3, respectively. The maximum output voltage is (255
output, 0V, is obtained for a value of 00
The reference voltage of the converters is the AV
0V to nearly AV
After reset, all four channels are disabled and the voltage on the DA0-3 outputs is 0V.
In Idle mode, the DAC channels may be enabled or disabled (to reduce power consumption). Two control modes are pro-
vided:
4.12.3 D/A Conversion
Output Signal
The DAC performs a linear conversion of the input digital value DACDATA7-0 registers to a unipolar analog output signal,
relative to the analog ground pin (AGND).
• 8-bit resolution
• Independent 4-channel D/A converter
• Fast settling time, 1 s typical, on 50 pF capacitive load
• Output range from AGND to AV
• Independent enable/disable for each channel
• All converters can be automatically disabled in Idle mode
• Low power consumption when enabled; zero power consumption when disabled
• Outputs drive 0V when disabled
• Automatic disable of all channels on entering Idle mode
• Selective disable of channels by software, before entering Idle mode
CC
Voltage Ratio to AV
.
Figure 63. Channel Data to Output Voltage Ratio Conversion
254/256
255/256
3/256
2/256
1/256
CC
CC
1
0
16
0
.
1
CC
(Continued)
2
analog power supply voltage. This allows full swing of the outputs from
3
179
256)
. . .
*
AV
CC
and is obtained for a value of FF
254
255
(256)
Level Data
[LSBits]
16
. The minimum
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CC
,