MCP45HVX1 Datasheet, PDF (30/100 Pages) Microchip Technology – Single-Resistor Network

MCP45HVX1
4.2.2 BROWN-OUT RESET
Each power system has its own independent Brown-
Out Reset circuitry. This is done so that regardless of
the power-down sequencing of the analog and digital
power rails, the wiper output will be forced to a default
value after the low-voltage conditions are met for either
power supply.
Table 4-4 shows the interaction between the analog
and digital BORs for the V+ and V_L voltages on the
wiper pin state.
TABLE 4-4: WIPER PIN STATE BASED
ON BOR CONDITIONS
V+ Voltage
V_L Voltage
V+ <
V_ABOR
V+  ^Comments
V_ABOR
V_L < V_DBOR
V_L  V_DBOR
Unknown
Unknown
Mid Scale
Wiper Wiper register
Register can be updated
Value ⁽¹⁾
Note 1: Default POR state of the Wiper register
value is the mid-scale value.
4.2.2.1 Digital Circuitry
When the device’s digital power supply powers-down,
the device V_L pin voltage will cross the digital V_DPOR/
V_DBOR voltage.
Once the V_L voltage decreases below the V_DPOR/
V_DBOR voltage, the following happens:
• Serial Interface is disabled
If the V_L voltage decreases below the V_RAM voltage,
the following happens:
• Volatile wiper registers may become corrupted
• TCON registers may become corrupted
Section 4.2.1, Power-on Reset describes what
occurs as the voltage recovers above the V_DPOR/
V_DBOR voltage.
Serial commands not completed due to a brown-out
condition may cause the memory location to become
corrupted.
The brown-out circuit establishes a minimum V_DBOR
threshold for operation (V_DBOR < 1.8V). The digital
BOR voltage (V_DBOR) is higher than the RAM retention
voltage (V_RAM) so that as the device voltage crosses
the digital BOR threshold, the value that is loaded into
the volatile Wiper register is not corrupted due to RAM
retention issues.
When V_L < V_DBOR, all communications are ignored and
potentiometer terminals are forced to the analog BOR
state.
Whenever V_L transitions from V_L < V_DBOR to V_L >
V_DBOR, (a POR event) the wiper’s POR/BOR value is
latched into the Wiper register and the volatile TCON
register is forced to the POR/BOR state.
When 1.8V  V_L, the device is capable of digital
operation.
Table 4-5 shows the digital potentiometer’s level of
functionality across the entire V_L range, while
Figure 4-4 illustrates the Power-Up and Brown-Out
functionality.
4.2.2.2 Analog Circuitry
The Analog Brown-Out-Reset (ABOR) is the case
where the device’s V+ pin has power applied (refer-
enced from V-) and the V+ pin voltage drops below the
trip point. In this case, the resistor network terminal’s
pins can become an unknown state.
DS20005304A-page 30
 2014 Microchip Technology Inc.