CS4172
CS4172
Single Air-Core Gauge Driver
Description
The CS4172 is a monolithic BiCMOS
integrated circuit used to translate a
digital 10-bit word from a micropro-
cessor/microcontroller to complemen-
tary DC outputs. The DC outputs
drive an air-core meter commonly
used in vehicle instrument panels. The
10 bits of data are used to linearly con-
trol the quadrature coils of the meter
directly with a 0.35¡ resolution and
±1.0¡ accuracy over the full 360¡ range
of the gauge. The interface from the
microcontroller is by a Serial Periph-
eral Interface (SPI) compatible serial
connection using up to a 2MHz shift
clock rate.
The digital code, which is directly pro-
portional to the desired gauge pointer
deflection, is shifted into a DAC and
multiplexer. These two blocks provide
a tangential conversion function to
change the digital data into the appro-
priate DC coil voltage for the angle
demanded. The tangential algorithm
creates approximately 40% more
torque in the meter movement than
does a sin-cos algorithm at 45¡, 135¡,
225¡, and 315¡ angles. This increased
torque reduces the error due to pointer
droop at these critical angles.
Each output buffer is capable of sup-
plying up to 80mA per coil and are
controlled by a common enable pin.
When OE is low the output buffers are
turned off but the logic portion of the
chip remains powered and continues
to operate normally.
The Serial Gauge Driver is self-protect-
ed against output short circuit condi-
tions. The output drivers are disabled
anytime the on-chip protection circuit-
ry detects a short circuit condition. The
outputs remain off until a falling edge
is presented on CS. If the short circuit
is still present the output drivers auto-
matically disable themselves again. A
thermal protection circuit limits the
junction temperature to approximately
160¡C for conditions of high supply
voltage and high ambient temperature.
The status pin (ST) reflects the state of
the outputs and is low whenever the
outputs are disabled.
Features
s
Serial Input Bus
s
2 MHz Operating
Frequency
s
Tangential Drive
Algorithm
s
80mA Drive Circuits
s
0.5¡ Accuracy (Typ.)
s
Power-On-Reset
s
Protection Features
Output Short Circuit
Overtemperature
Package Options
16 Lead PDIP
SIN
-
SIN
+
Gnd
V
BB
SO
1
COS
+
COS
-
Gnd
Gnd
NC
ST
CS
SCLK
Block Diagram
V
CC
V
BB
SI
V
CC
OE
POR
LOGIC
SI
SCLK
CS
SIN
+
Serial
to
Parallel
Shift
Register
V
TOP
D0 Ð D6
16 Lead SO Wide
(internally fused leads)
SIN
-
1
7 Bit
DAC
V
VAR
V
BAT
MUX
SIN
Ð
COS
+
COS
-
SO
Gnd
Gnd
ST
CS
SCLK
COS
+
SIN
+
V
BB
Gnd
SO
D7 Ð D9
OC
COS
Ð
R FAULT S
Latch S
ST
Output
Amplifiers
Gnd
SI
V
CC
OE
POR
OE
Gnd
Cherry Semiconductor Corporation
2000 South County Trail, East Greenwich, RI 02818
Tel: (401)885-3600 Fax: (401)885-5786
Email: info@cherry-semi.com
Web Site: www.cherry-semi.com
Rev. 4/19/99
1
A
¨
Company
CHERRY [ CHERRY SEMICONDUCTOR CORPORATION ]
