MCP4431 Microchip Technology Inc., MCP4431 Datasheet - Page 46

• Manufacturer Part Number: MCP4431
• Description: 7/8-bit Volatile Quad Digital Pot With I 2c Interface
• Manufacturer: Microchip Technology Inc.

MCP443X/5X
5.2
Each tap point (between the R
connection point for an analog switch. The opposite
side of the analog switch is connected to a common
signal which is connected to the Terminal W (Wiper)
pin.
A value in the volatile wiper register selects which
analog switch to close, connecting the W terminal to
the selected node of the resistor ladder.
The wiper can connect directly to Terminal B or to
Terminal A. A zero scale connections, connects the
Terminal W (wiper) to Terminal B (wiper setting of
000h). A full scale connection, connects the Terminal W
(wiper) to Terminal A (wiper setting of 100h or 80h). In
these configurations, the only resistance between the
Terminal W and the other Terminal (A or B) is that of the
analog switches.
A wiper setting value greater than full scale (wiper
setting of 100h for 8-bit device or 80h for 7-bit devices)
will also be a Full Scale setting (Terminal W (wiper)
connected to Terminal A).
wiper setting map.
Equation 5-2
determine the resistance between the wiper and
terminal B.
EQUATION 5-2:
TABLE 5-1:
DS22267A-page 46
3FFh –
07Fh –
03Fh –
Wiper Setting
081h
080h
041h
040h
001h
000h
7-bit
N = 0 to 256 (decimal)
N = 0 to 128 (decimal)
R
R
Wiper
WB
WB
3FFh –
0FFh –
07Fh –
8-bit
101h
100h
081h
080h
001h
000h
=
=
illustrates the calculation used to
--------------

--------------

R
R
256
128
AB
AB
VOLATILE WIPER VALUE VS.
WIPER POSITION MAP
Reserved (Full Scale (W = A)),
Increment and Decrement
commands ignored
Full Scale (W = A),
Increment commands ignored
W = N
W = N (Mid Scale)
W = N
Zero Scale (W = B)
Decrement command ignored
N
N


+
+
R
WB
R
R
W
W
Table 5-1
CALCULATION
Properties
8-bit Device
7-bit Device
S
illustrates the full
resistors) is a
5.3
Shutdown is used to minimize the device’s current
consumption. The MCP44XX has one method to
achieve this. This is:
•
This is different from the MCP42XXX devices in that the
Hardware Shutdown Pin (SHDN) has been replaced by
a RESET pin. The Hardware Shutdown Pin function is
still available via software commands to the TCON
register.
5.3.1
The Terminal Control (TCON) register is a volatile
register used to configure the connection of each
resistor network terminal pin (A, B, and W) to the
Resistor Network. These registers are shown in
Register 4-1
The RxHW bits forces the selected resistor network
into the same state as the MCP42X1’s SHDN pin.
Alternate low power configurations may be achieved
with the RxA, RxW, and RxB bits.
When the RxHW bit is ‘0’:
• The P0A, P1A, P2A, and P3A terminals are
• The P0W, P1W, P2W, and P3W terminals are
The RxHW bit does NOT corrupt the values in the
Volatile Wiper Registers nor the TCON register. When
the Shutdown mode is exited (RxHW bit = 1):
• The device returns to the Wiper setting specified
• The TCON register bits return to controlling the
FIGURE 5-2:
State (RxHW = ‘
Terminal Control Register (TCON)
disconnected
simultaneously connect to the P0B, P1B, P2B,
and P3B terminals, respectively (see
Note:
by the Volatile Wiper value
terminal connection state
Shutdown
TERMINAL CONTROL REGISTER
(TCON)
When the RxHW bit forces the resistor
network into the hardware SHDN state,
the state of the TCON0 or TCON1
register’s RxA, RxW, and RxB bits is
overridden (ignored). When the state of
the RxHW bit no longer forces the resistor
network into the hardware SHDN state,
the TCON0 or TCON1 register’s RxA,
RxW, and RxB bits return to controlling the
terminal connection state. In other words,
the RxHW bit does not corrupt the state of
the RxA, RxW, and RxB bits.
and
A
Register
B
0
’).
Resistor Network Shutdown
 2010 Microchip Technology Inc.
4-2.
W
Figure
5-2)