MCP4332-503E/ST Microchip Technology, MCP4332-503E/ST Datasheet - Page 80

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MCP4332-503E/ST

Manufacturer Part Number
MCP4332-503E/ST
Description
IC DGTL POT QUAD 50K 14TSSOP
Manufacturer
Microchip Technology
Datasheet

Specifications of MCP4332-503E/ST

Taps
129
Resistance (ohms)
50K
Number Of Circuits
4
Temperature Coefficient
150 ppm/°C Typical
Memory Type
Volatile
Interface
SPI Serial
Voltage - Supply
1.8 V ~ 5.5 V
Operating Temperature
-40°C ~ 125°C
Mounting Type
Surface Mount
Package / Case
14-TSSOP
Resistance In Ohms
50K
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
MCP433X/435X
Figure B-3
for V
show that as the resistor ladder wiper node voltage
(V
resistance increases. These graphs also show the
different resistance characteristics of the NMOS and
PMOS transistors that make up the wiper switch. This
is demonstrated by the wiper code resistance curve,
which does not mirror itself around the mid-scale code
(wiper code = 128).
So why is the R
resistance at about mid-scale (wiper code = 128) and
the R
This requires understanding low-voltage transistor
characteristics as well as how the data was measured.
FIGURE B-3:
Wiper Code and Temperature
(V
I
FIGURE B-4:
Wiper Code and Temperature
(V
DS22242A-page 80
W
WCn
DD
DD
= 480
DD
BW
220
200
180
160
140
120
100
2020
1520
1020
= 5.5V, I
= 1.8V, I
) approaches the V
80
60
40
20
520
20
voltages of 5.5, 3.0, 1.8 Volts. These graphs
graphs showing the issue at code 160?
0
0
µ
and
A).
-40C @ 3.0V
-40C @5.5V
-40C @ 1.8V
+25C @ 1.8V
+85C @ 1.8V
+125C @ 1.8V
W
W
Figure B-4
= 900 UA; V
= 260
W
64
64
graphs showing the maximum
+25C @ 3.0V
+25C @ 5.5V
Wiper Resistance (R
Wiper Resistance (R
µ
Wiper Code
Wiper Code
A).
show the wiper resistance
DD
128
128
/2 voltage, the wiper
DD
+85C @ 3.0V
+85C @ 5.5V
= 3.0V,
192
192
+125C @ 3.0V
+125C @ 5.5V
W
W
) vs.
) vs.
256
256
The method in which the data was collected is
important to understand.
technique that was used to measure the R
resistance. In this technique Terminal A is floating and
Terminal B is connected to ground. A fixed current is
then forced into the wiper (I
wiper voltage (V
current through R
voltage difference between the wiper (V
Terminal A (V
calculated, see
change the wiper voltage (V
device’s wiper resistance (R
FIGURE B-5:
Figure B-6
network where the R
resistors. These resistors are polysilicon devices. Each
wiper switch is an analog switch made up of an NMOS
and PMOS transistor. A more detailed figure of the
wiper switch is shown in
resistance is influenced by the voltage on the wiper
switches nodes (V
influences the characteristics of the wiper switch, see
Figure
The NMOS transistor and PMOS transistor have
different characteristics. These characteristics as well
as the wiper switch node voltages determine the R
resistance at each wiper code. The variation of each
wiper switch’s characteristics in the resistor network is
greater then the variation of the R
The voltage on the resistor network node (V
dependent upon the wiper code selected and the
voltages applied to V
voltage to V
the transistor is turned on. When the transistor is
weakly turned on the wiper resistance R
When the transistor is strongly turned on, the wiper
resistance (R
floating
A
B
B-4.
V
V
A
B
W
shows a block diagram of the resistor
W
W
or V
A
) will be in the typical range.
), the wiper resistance (R
Figure
W
WCn
G
V
BW
) is measured. Forcing a known
, V
W
I
A
W
AB
, V
voltage determines how strongly
W
R
B-5. Changes in I
(I
 2010 Microchip Technology Inc.
B
BW
resistor is a series of 256 R
W
and V
and V
) and then measuring the
W
W
and R
Figure B-5
W
).
R
) and the corresponding
R
Figure
WCn
). This may effect the
BW
W
W
. The wiper switch V
S
= (V
). Temperature also
= V
W
resistors.
B-7. The wiper
Measurement.
W
W
-V
/I
W
W
W
A
shows the
will be high.
BW
)/I
W
current will
) can be
W
W
and R
WCn
) and
) is
W
W
G
S

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