P87LPC769 NXP Semiconductors, P87LPC769 Datasheet - Page 16

• Manufacturer Part Number: P87LPC769
• Description: The P87LPC769 is a 20-pin single-chip microcontroller designed forlow pin count applications demanding high-integration, low costsolutions over a wide range of performance requirements
• Manufacturer: NXP Semiconductors

Philips Semiconductors
Digital to Analog Converter (DAC) Outputs
The P87LPC769 provides a two channel, 8-bit DAC function. DAC0
is also a part of the A/D Converter and it should not be enabled
while the A/D is active. Digital outputs must be disabled on the DAC
output pins while the corresponding DAC is enabled, as described in
the section Analog Functions.
The DACs use the power supply as the references: V
upper reference and V
generated by a tap from a resistor ladder and is not buffered. The
maximum resistance to V
Care must be taken with the loading of the DAC outputs in order to
2002 Mar 12
Low power, low price, low pin count (20 pin)
microcontroller with 4 kB OTP 8-bit A/D, and DAC
SS
DD
as the lower reference. The DAC output is
or V
SS
from a DAC output is 10k .
ADCON
D/A CONVERTER
DD
Figure 4. DAC Block Diagram
as the
DACn
13
avoid distortion of the output voltage. DAC accuracy is affected by
noise generated on-chip and elsewhere in the application. Since the
P87LPC769 power pins are used for the DAC references, the power
supply also affects the accuracy of the DAC outputs.
The ideal DAC output may be calculated as follows:
where DAC value is the contents of the relevant DAC register:
DAC0 or DAC1.
Result + (DAC Value ) 0.5)
ENDACn
V
DACn pin
V
REF
REF
+ = V
– = V
DD
ss
V
DD
256
* V
SS
P87LPC769
SU01371
Preliminary data