Datasheet

MCP4011/2/3/4
DS21978C-page 28 © 2006 Microchip Technology Inc.
4.2 Power-up
When the device powers up (rising V
DD
crosses the
Trip Point Voltage (V
TP
)), the “default” wiper setting is
restored. Table 4-1 shows the default value loaded into
the wiper on POR/BOR.
TABLE 4-1: DEFAULT POR WIPER
SETTING SELECTION
While V
DD
< V
min
(1.8V), the electrical performance
may not meet the data sheet specifications (see
Figure 4-2). The wiper state may be unknown. Also, the
device may be capable of incrementing or decrement-
ing, if a valid command is detected on the CS
and U/D
pins.
4.3 Brown Out
If the device V
DD
is below the specified minimum
voltage, care must be taken to ensure that the CS
and
U/D pins do not “create” any of the serial commands.
When the device V
DD
drops below V
MIN
(1.8V), the
electrical performance may not meet the data sheet
specifications (see Figure 4-2). The wiper state may be
unknown. Also, the device may be capable of
incrementing or decrementing, if a valid command is
detected on the CS
and U/D pins.
When the device voltage rises from below the power-
up trip point (V
TP
) into the valid operation voltage
range, the wiper state will be forced to the default POR
wiper setting (see Ta ble 4-1 ).
4.4 Serial Interface Inactive
The serial interface is inactive any time the CS pin is at
V
IH
and all write cycles are completed.
FIGURE 4-2: Power-up and Brown-out.
Package
Code
Default
POR
Wiper
Setting
Wiper
Code
Typical
R
AB
Value
-202 Mid-scale 1Fh 2.1 kΩ
-502 Mid-scale 1Fh 5.0 kΩ
-103 Mid-scale 1Fh 10.0 kΩ
-503 Mid-scale 1Fh 50.0 kΩ
V
TP
V
SS
V
DD
1.8V
POR Trip Point (on Rising V
DD
)
Outside Device Operation
Wiper Forced to Default POR Setting