Datasheet

Digital Analog Converter (DAC_8B5V)
MC9S12G Family Reference Manual, Rev.1.23
Freescale Semiconductor 579
The DAC resistor network itself can work on two different voltage ranges:
Table 17-7 shows the control signal decoding for each mode. For more detailed mode description see the
sections below.
17.5.2 Mode “Off”
The “Off” mode is the default mode after reset and is selected by DACCTL.DACM[2:0] = 0x0. During this
mode the DAC resistor network and the operational amplifier are disabled and all switches are open. This
mode provides the lowest power consumption. For decoding of the control signals see Table 17-7.
17.5.3 Mode “Operational Amplifier”
The “Operational Amplifier” mode is selected by DACCTL.DACM[2:0] = 0x1. During this mode the
operational amplifier can be used independent from the DAC resister network. All required amplifier
signals, AMP, AMPP and AMPM are available on the pins. The DAC resistor network output is
disconnected from the DACU pin. The connection between the amplifier output and the negative amplifier
input is open. For decoding of the control signals see Table 17-7.
Operational amplifier 001 disabled enabled disabled depend on AMPP
and AMPM input
Unbuffered DAC 100 enabled disabled unbuffered resistor
output voltage
disconnected
Unbuffered DAC with
Operational amplifier
101 enabled enabled unbuffered resistor
output voltage
depend on AMPP
and AMPM input
Buffered DAC 111 enabled enabled disconnected buffered resistor
output voltage
Table 17-6. DAC Resistor Network Voltage ranges
DAC Mode Description
Full Voltage Range (FVR) DAC resistor network provides a output voltage over the complete input voltage range,
default after reset
Reduced Voltage Range DAC resistor network provides a output voltage over a reduced input voltage range
Table 17-7. DAC Control Signals
DACM
DAC resistor
network
Operational
Amplifier
Switch S1 Switch S2 Switch S3
Off 000 disabled disabled open open open
Operational amplifier 001 disabled enabled closed open open
Unbuffered DAC 100 enabled disabled open open closed
Unbuffered DAC with
Operational amplifier
101 enabled enabled closed open closed
Buffered DAC 111 enabled enabled open closed open
Table 17-5. DAC Modes of Operation