ML51/ML54/ML56
Sep. 01, 2020
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ML51/M
L54
/M
L56
Series
Tec
hnical Reference
Manual
6.14 Voltage Reference (V
REF
)
The V
REF
pin is for analog multiplexer, such as ADC, ACMP. It default be used as an external
source(set ENVRF = 0). It also could be configurable as on-chip reference voltage generator (V
REF_IN
)
by setting ENVRF = 1 (seeFigure 6.14-1 VREF Block Diagram). The output voltage is selectable by
setting VRFSEL[2:0]. The maximum load of the V
REF_IN
must be less than 200 uA to AV
SS
. Set pre-load
is to reduce stable time of V
REF_IN
. At first enable V
REF_IN
and turn on pre-load at the same time, the
minimum stable time of pre-load on the V
REF_IN
must be greater than 3 ms. After the V
REF_IN
stable,
user should be turn off pre-load to avoid any interference on analog multiplexer. Pre-load is only for
internal V
REF
use. For detailed electrical characteristics, refer to the
Table36-10. Internal V
REF
.
000
VRFSEL[2:0]
(VRFCON[6:4])
V
REF
to Analog MUX
4.096 V
3.072 V
2.560 V
2.048 V
1.538 V
001
010
011
100
ENVRF
(VRFCON[0])
Pre-
load
ENLOAD
(VRFCON[1])
1 uF
Recommended
External
Capacitor
Figure 6.14-1 V
REF
Block Diagram
ENLOAD
Internal V
REF
ENVRF
Min. = 3 ms
Note: Add a 1uF capacitor on V
REF
pin.
Figure 6.14-2 Pre-load Timing
