NXP Semiconductors LPC24XX UM10237 - Manual (Page 675)

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User manual Rev. 04 — 26 August 2009 675 of 792
NXP Semiconductors
UM10237
Chapter 29: LPC24XX Digital-to Analog Converter (DAC)
5. Operation
Bits 21:20 of the PINSEL1 register ( Section 9–5.2 “Pin Function Select Register 1
(PINSEL1 - 0xE002 C004)” on page 180 ) control whether the DAC is enabled and
controlling the state of pin P0.26/AD0.3/AOUT/RXD3. When these bits are 10, the DAC is
powered on and active.
The settling times noted in the description of the BIAS bit are valid for a capacitance load
on the AOUT pin not exceeding 100 pF. A load impedance value greater than that value
will cause settling time longer than the specified time. One or more graph(s) of load
impedance vs. settling time will be included in the final data sheet.
Table 599: D/A Converter Register (DACR - address 0xE006 C000) bit description
Bit Symbol Value Description Reset
Value
5:0 - Reserved, user software should not write ones to reserved
bits. The value read from a reserved bit is not defined. NA
15:6 VALUE After the selected settling time after this field is written with a
new VALUE, the voltage on the A
OUT
pin (with respect to V
SSA
)
is VALUE/1024
× VREF.
0
16 BIAS 0 The settling time of the DAC is 1
μs max, and the maximum
current is 700
μA.
0
1 The settling time of the DAC is 2.5
μs and the maximum
current is 350
μA.
31:17 - Reserved, user software should not write ones to reserved
bits. The value read from a reserved bit is not defined. NA