• VDACn_OPAx_CTRL
• VDACn_OPAx_TIMER
• VDACn_OPAx_MUX
24.3.1.1 Enable Sources
Opamp can be enabled either with software or PRS. The default source is software. Setting PRSEN to 1 in VDACn_OPAx_CTRL ena-
bles PRS mode. In PRS mode, opamp has two options, which are selectable with PRSMODE in VDACn_OPAx_CTRL. If PRSMODE is
configured to TIMED, opamp is turned on on the positive edge of PRS and stays on until PRS goes low. If PRSMODE is configured to
PULSED, opamp is turned on the positive edge of PRS and stays on based on the timer configurations in VDACn_OPAxTIMER. The
PRS channel is selected by PRSSEL in VDACn_OPAx_CTRL.
24.3.1.2 Warmup Time
When an opamp is enabled some initialization time is required. The warm up period is programmable with WARMUPTIME in
VDACn_OPAx_TIME. The OPAxWARM bit in VDACn_STATUS are set when the warmup period has completed.
The warm up period depends on the selected DRIVESTRENGTH in VDACn_OPAx_CTRL.
Table 24.1. OPAMP Warmup Time
DRIVESTRENGTH
WARMUPTIME (µs)
0
100
1
85
2
8
3
6
24.3.1.3 Settle Time
After an opamp is enabled and the warmed-up time has elapsed the output settles externally. The settle period is programmable with
SETTLETIME in VDACn_OPAx_TIME. The OPAxOUTVALID bit in VDACn_STATUS is set when the settle period has completed. When
in use by the VDAC the default settling time is used.
The settling period depends on the load at opamp output and DRIVESTRENGTH of the opamp.
Table 24.2 OPAMP Settling Time on
specifies SETTLETIME settings for a load of 1KOhm and 75pF.
Table 24.2. OPAMP Settling Time
DRIVESTRENGTH
SETTLETIME (µs)
0
60
1
25
2
3
3
1
24.3.1.4 Startup Delay
Each opamp has an option to delay the warm up period. The startup delay is programmable with STARTDLY in VDACn_OPAx_TIME. If
STARTDLY is programmed to a non-zero value, the opamp is warmed up after SWARMUPTIME, and the output settles after
SWARSETTLETIME.
24.3.1.5 Power Supply
The opamp module power (V
OPA
) is derived from the AVDD supply pin.
Reference Manual
OPAMP - Operational Amplifier
silabs.com
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