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UM10360_0
© NXP B.V. 2009. All rights reserved.
User manual
Rev. 00.06 — 5 June 2009
557 of 808
1.
Basic configuration
The DAC is configured using the following registers:
1. Power: The DAC is always connected to V
DDA
. Register access is determined by
PINSEL and PINMODE settings (see below).
2. Clock: In the PCLKSEL0 register (
), select PCLK_DAC.
3. Pins: Enable the DAC pin through the PINSEL registers. Select pin mode for port pin
with DAC through the PINMODE registers (
). This must be done before
accessing any DAC registers.
4. DMA: The DAC can be connected to the GPDMA controller (see
). For
GPDMA connections, see
2.
Features
•
10-bit digital to analog converter
•
Resistor string architecture
•
Buffered output
•
Power-down mode
•
Selectable speed vs. power
3.
Pin description
gives a brief summary of each of DAC related pins.
Remark:
When the DAC is not used, the V
DDA
and VREFP pins must be connected to the
power supply, and pin V
SSA
must be grounded. These pins should
not
be left floating.
UM10360
Chapter 30: LPC17xx Digital-to-Analog Converter (DAC)
Rev. 00.06 — 5 June 2009
User manual
Table 519. D/A Pin Description
Pin
Type
Description
AOUT
Output
Analog Output.
After the selected settling time after the DACR is
written with a new value, the voltage on this pin (with respect to
V
SSA
) is VALUE/1024
×
VREF.
VREFP
Reference
Voltage Reference.
This pin provides a voltage reference level for
the ADC and DAC.
Note: this pin should be tied to V
DD(3V3)
if the
ADC and DAC are not used.
V
DDA
, V
SSA
Power
Analog Power and Ground.
These should be nominally the same
voltages as V
DD(3V3)
and V
SS
, but should be isolated to minimize
noise and error.
Note: this pin should be tied to V
DD(3V3)
if the
ADC and DAC are not used.