CS289
CS289
20mA Air-Core Tachometer Drive Circuit
Description
The CS289 is specifically designed
for use with air-core meter move-
ments. The IC has charge pump cir-
cuitry for frequency-to-voltage con-
version, a shunt regulator for stable
operation, a function generator, and
sine and cosine amplifiers. The
buffered sine and cosine outputs
will typically sink or source 20mA.
Features
s
Single Supply Operation
s
On-Chip Regulation
s
20mA Output Drive
Capability
Absolute Maximum Ratings
Supply Voltage (V
CC
)......................................................................................20V
Operating Temperature ............................................................Ð40¡C to +100¡C
Junction Temperature..................................................................Ð40¡C to 150¡C
Storage Temperature.................................................................Ð65¡C to +150¡C
Lead Temperature Soldering
Wave Solder (through hole styles only)...........10 sec. max, 260¡C peak
Reflow (SMD styles only)............60 sec. max above 183¡C, 230¡C peak
Block Diagram
Package Options
14L PDIP
V
Z
1
Pwr Gnd
V
CC
V
COS
V
REG
S
Q
IN
S
Q
OUT
F/V
OUT
Pwr Gnd
V
CC
V
COS
V
REG
S
Q
IN
S
Q
OUT
F/V OUT
V
SINE
NC
V
BIAS
C
P
Ð
C
P
+
Gnd
Regulator
Charge
Pump
20L SOIC Wide
(internally fused leads)
V
Z
1
V
SINE
V
CC
V
COS
V
REG
Gnd
Gnd
Gnd
Gnd
S
Q
IN
S
Q
OUT
F/V
OUT
Function
Generator
V
BIAS
Ð +
Gnd
Gnd
Gnd
Gnd
C
P
Ð
V
Z
V
SINE
V
BIAS
C
p
Ð
C
P
+
Gnd
C
P
+
NC
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. 3/8/99
1
A
¨
Company
CS289
Electrical Characteristics: (V
CC
= 13.1V, -30¡C ² T
A
² 85¡C)
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
Supply Current (Note 2)
V
CC
= 15.0V
V
CC
= 13.1V
V
CC
= 11.3V
I
REG
= 4.3mA
I
REG
= 0 to 5mA
T = 25¡C
I
SQ
OUT = 5mA, I
SQ
IN = 500µA
I
SQ
OUT = 16V, V
SQ
IN = 0V
C
P
+ = 0, T = 25¡C
V
SQ
IN = 0 (zero input),
Æ
= 0¡
V
COS
= 0 (Note 1),
Æ
= 270¡
1.8
6.3
-1.5
-0.55
3.8
-3.8
0.1
7.7
54
60
60
8.5
0.10
2.0
0.20
1
2.1
7.1
65
65
9.3
0.20
4.0
0.55
10
15
2.4
7.9
1.5
mA
mA
mA
V
V
mA
V
µA
nA
V
%
V
V
V
mA
mA
V
V
mA
mA
V
Regulated Voltage
Regulation
Signal Input Current
Saturation Voltage
Leakage Current
Input Current
F to V Output
Linearity
V
sine
at
Æ
= 0¡
MAX V
sine+
MAX V
sine-
Coil Drive Current
E
O
vs. Frequency
V
COS
= 0 (Note 1),
Æ
= 270¡, T = 25¡C
V
SQ
IN = 0 (zero input),
Æ
= 0¡
V
COS
= 0 (Note 1),
Æ=90¡
V
COS
= 0 (Note 1),
Æ
= 270¡
V
COS
= 0 (Note 1),
Æ
= 90¡, T = 25¡C
V
COS
= 0 (Note 1),
Æ
= 270¡
V
SQ
IN = 0 (zero input),
Æ
= 0¡
V
sine
= 0 (Note 1),
Æ
= 180¡
V
SQ
IN = 0 (zero input),
Æ
= 0¡
V
sine
= 0 (Note 1),
Æ
= 180¡
0.00
4.5
-4.5
20
20
0.55
5.8
-5.8
25
25
5.8
-5.8
25
25
5.85
MAX V
COS+
MAX V
COS-
Coil Drive Current
3.8
-3.8
4.5
-4.5
20
20
External Voltage Ref.
4.98
5.40
Note 1: V
sine
measured V
sine
to V
Z
. V
COS
measured V
COS
to V
Z
. All other voltages specified are measured to ground.
Note 2: Max PWR dissipation ²V
CC
X I
CC
- (V
2
I
sine
+ V12 I
COS
).
Package Pin Description
PACKAGE PIN #
PIN SYMBOL
FUNCTION
20L SO
(internally fused leads)
1
2
3
4, 5, 6, 7,
14, 15, 16, 17
8
9
10
11
14L PDIP
1
2
4
7
5
6
3
8
V
Z
V
sine
V
BIAS
Gnd
C
PÐ
C
P+
NC
F/V
OUT
External Zener reference.
Sine output signal.
Test pin or "0" calibration pin.
Analog Ground connection.
Negative input to charge pump.
Positive input to charge pump.
No Connection
Output voltage proportional to input signal frequency.
2
CS289
Package Pin Description: continued
PACKAGE PIN #
PIN SYMBOL
FUNCTION
20L SO
12
13
18
19
20
14L PDIP
9
10
11
12
13
14
S
Q
OUT
S
Q
IN
V
REG
V
COS
V
CC
Pwr Gnd
Buffered square wave output signal.
Speed or RPM input signal.
Voltage regulator output.
Cosine output signal.
Supply voltage.
Power Ground connection.
Note 1: V
sine
measured V
sine
to V
Z
. V
COS
measured V
COS
to V
Z
. All other voltages specified are measured to ground.
Note 2: Max PWR dissipation ²V
CC
X I
CC
- (V
2
I
sine
+ V12 I
COS
).
Typical Performance Characteristics
Output Angle in Polar Form
Charge Pump Output Voltage
Relationship of EQ,
Q
and Frequency
+
V COS
Q
P
F/V Output (V)
7.1
6
COSINE
OUTPUT
Q
V
P
SIN
Q
5
4
3
Ð
V
Z
+
SINE OUTPUT
2.1
F/V
OUT
= 2.0V + FREQ X C
T
X R
T
X V
REG
0
45û
90û
135û
180û
225û
270û
Ð
Frequency/Output Angle (°)
Function Generator Output Voltage
2.1
4.5
3.5
V
SINE
V
SINE
, V
COS
(V)
2.5
1.5
V
Z
-1.5
-2.5
-3.5
-4.5
0
45û
90û 135û 180û 225û
Tachometer Angular Deflection (°)
270û
4.5V
4.5V
V
COS
3.8
5.45
7.1
3
CS289
Circuit Description
Charge Pump
Function Generator/Sine and Cosine Amplifiers
The input frequency is buffered through a transistor, then
applied to the charge pump for frequency-to-voltage con-
version (Figure 1). The charge pump output voltage, EÆ,
will range from 2.1V with no input (Æ= 0¡) to 7.1V at
Æ
=
270¡. The charge that appears on C
T
is reflected to C
OUT
through a Norton amplifier. The frequency applied at
S
Q
IN charges and discharges C
T
through R
1
and R
2
. C
OUT
reflects the charge as a voltage across resistor R
T
.
The output waveforms of the sine and cosine amplifiers
are derived by On-Chip Amplifier/Comparator circuitry.
The various trip points for the circuit (i.e. 90¡, 180¡, 270¡)
are determined by an internal resistor divider connected
to the voltage regulator. The voltage EÆ is compared to
the divider network by the function generator circuitry.
Use of an external zener reference at V
Z
allows both sine
and cosine amplifiers to swing positive and negative with
respect to this reference. The output magnitudes and
directions have the relationship as shown in Typical
Characteristics diagrams.
Note: Pin connections referenced are for the 14L DIP.
Function Generator Output (Æ): V
CC
=13.1V, T
A
=25¡C
Æ=ArcTan
V
sine
(Measured angle after calibration at 180¡C)
V
cos
1kW
For
Æ
A
=45¡, 90¡, 135¡, 180¡, 225¡, 270¡, (Desired angle)
(Æ
A
-Æ
M
)²4.0¡
Temperature Sensitivity: V
CC
=13.1V
ÆÆ
MT
=Æ
M
(T=25¡C) -ÆM (-20¡C²T²+85¡C)
(ÆÆ
MT
)²3.5¡C, -20¡C²T²+85¡C
Voltage Sensitivity: T
A
=25¡C
ÆÆ
MV
=Æ
M
(V
CC
=13.1V) -Æ
M
(11.3V²V
CC
²15V)
(ÆÆ
MV
)²2¡, 11.3V²V
CC
²15V
V
Z
100W
B+
V
SINE
V
BIAS
Gnd
V
COS
V
REG
V
CC
15
B+
18V
R2
2kW
TACH INPUT
2kW
E
Q
S
Q
OUT
F-V
OUT
C
OUT
1mF
±10%
S
Q
IN
CS289
R
T
180kW
*
C
P
Ð
80mH
225
R1
SINE
80mH
225
1kW
C
T
0.01mF
ZENER
5.4V
* ADJUST FOR TRIMMING
Figure 1. Functional Diagram of CS289 Circuit.
4
C
P
+
Gnd
NC
CS289
Tachometer Application
RPM x # OF CYL. = Frequency
60
2
V
F/V
OUT
= 2.1 + Frequency x C
T
x R
T
(V
REG
-0 .7)
The above equations were used in calculating the follow-
ing values, where V
F/V
OUT
= 7.1V at =270¡ and C
T
= 0.01 F.
4 cylinder: Freq = 200Hz, R
T
= 320k½
6 cylinder: Freq = 300Hz, R
T
= 220k½
8 cylinder: Freq = 400Hz, R
T
= 150k½
Typical values shown above apply to a nominal value of
V
REG
of 8.5 volts. It must be realized that trimming of R
T
will be necessary to compensate for variations in regula-
tor voltage from one unit to another.
An alternative to this adjustment is to replace R
2
with a
potentiometer, as shown in Figure 2.
Partial schematic shown in Figure 3 represents one met-
hod for use with DC applications instead of frequency.
10kW
TRIM
I
OUT/EQ
S
Q
OUT
F-V
OUT
V
COS
V
REG
S
Q
IN
F-V
OUT
R
T
R
T
C
P
Gnd
C
P
+
C
P
Ð
C
P
V
BIAS
Gnd
C
P
+
C
P
Ð
NC
2.1V
0.7V
C
T
I
IN
1kW
Figure 2: Alternate Trimming Method
Figure 3: DC Application
5
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