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PDF CS8191XDWFR20 Data sheet ( Hoja de datos )
| Número de pieza | CS8191XDWFR20 | |
| Descripción | Precision Air-Core Tach/Speedo Driver with Short Circuit Protection | |
| Fabricantes | Cherry Semiconductor Corporation | |
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CS8191
Precision Air-Core Tach/Speedo Driver
with Short Circuit Protection
Description
The CS8191 is specifically designed
for use with 4 quadrant air-core
meter movements. The IC includes
an input comparator for sensing
input frequency such as vehicle
speed or engine RPM, a charge
pump for frequency to voltage con-
version, a bandgap reference for
stable operation and a function
generator with sine and cosine
amplifiers that differentially drive
the motor coils.
The CS8191 has a higher torque
output and better output signal
symmetry than other competitive
parts (CS289, and LM1819). It is
protected against short circuit and
overvoltage (60V) fault conditions.
Enhanced circuitry permits func-
tional operation down to 8V.
Absolute Maximum Ratings
Supply Voltage ( ² 100ms pulse transient) ...........................................VCC = 60V
(continuous) ..................................................................VCC = 24V
Operating Temperature Range ........................................................-40¡C to +105¡C
Junction Temperature Range ...........................................................-40¡C to +150¡C
Storage Temperature Range.............................................................-55¡C to +165¡C
Electrostatic Discharge (Human Body Model) ...................................................4kV
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
BIAS
CP+
SQOUT
FREQIN
Gnd
Gnd
COS+
COS-
VCC
Charge Pump
Input
Comp.
+
Ð
Voltage
Regulator
VREG
7.0V
COS
Output
+
Ð
Function
Generator
Ð
+
SINE
Output
+
Ð
High Voltage, Short
Circuit Protection
F/VOUT
CP-
VREG
Gnd
Gnd
SINE+
SINE-
Features
s Direct Sensor Input
s High Output Torque
s Wide Output Voltage
Range
s High Impedance Inputs
s Accurate down to 10V VCC
s Fault Protection
Overvoltage
Short Circuit
s Low Voltage Operation
Package Options
16 Lead PDIP
(internally fused leads)
VCC 1
VREG 2
BIAS 3
Gnd 4
Gnd 5
COS- 6
SINE- 7
FREQIN 8
16 F/VOUT
15 CP+
14 CP-
13 Gnd
12 Gnd
11 COS+
10 SINE+
9 SQOUT
20 Lead SOIC
(internally fused leads)
VCC 1
VREG 2
BIAS 3
NC 4
Gnd 5
Gnd 6
NC 7
COS- 8
SIN- 9
FREQIN 10
20 F/VOUT
19 CP+
18 CP-
17 NC
16 Gnd
15 Gnd
14 NC
13 COS+
12 SIN+
11 SQOUT
Rev 3/9/99
Cherry Semiconductor Corporation
2000 South County Trail, East Greenwich, RI 02818
Tel: (401)885-3600 Fax: (401)885-5786
Email: [email protected]
Web Site: www.cherry-semi.com
1 A ¨ Company
1 page  
Circuit Description and Application Notes
The CS8191 is specifically designed for use with air-core
meter movements. It includes an input comparator for
sensing an input signal from an ignition pulse or speed
sensor, a charge pump for frequency to voltage conver-
sion, a bandgap voltage regulator for stable operation,
and a function generator with sine and cosine amplifiers
to differentially drive the motor coils.
From the simplified block diagram of Figure 5A, the
input signal is applied to the FREQIN lead, this is the
input to a high impedance comparator with a typical pos-
itive input threshold of 2.7V and typical hysteresis of
0.4V. The output of the comparator, SQOUT, is applied to
the charge pump input CP+ through an external capacitor
CT. When the input signal changes state, CT is charged
or discharged through R3 and R4. The charge accumulat-
ed on CT is mirrored to C4 by the Norton Amplifier cir-
cuit comprising of Q1, Q2 and Q3. The charge pump out-
put voltage, F/VOUT, ranges from 2V to 6.3V depending
on the input signal frequency and the gain of the charge
pump according to the formula:
Design Example
Maximum meter Deflection = 270¡
Maximum Input Frequency = 350Hz
1. Select RT and CT
Q = AGEN ´ ÆF/V
ÆF/V = 2 ´ FREQ ´ CT ´ RT ´ (VREG Ð 0.7V)
Q = 970 ´ FREQ ´ CT ´ RT
Let CT = 0.0033µF, Find RT
270¡
RT = 970 ´ 350Hz ´ 0.0033µF
RT = 243k½
RT should be a 250k½ potentiometer to trim out any inac-
curacies due to IC tolerances or meter movement pointer
placement.
F/VOUT = 2.0V + 2 ´ FREQ ´ CT ´ RT ´ (VREG Ð 0.7V)
RT is a potentiometer used to adjust the gain of the F/V
output stage and give the correct meter deflection. The
F/V output voltage is applied to the function generator
which generates the sine and cosine output voltages. The
output voltage of the sine and cosine amplifiers are
derived from the on-chip amplifier and function genera-
tor circuitry. The various trip points for the circuit (i.e., 0¡,
90¡, 180¡, 270¡) are determined by an internal resistor
divider and the bandgap voltage reference. The coils are
differentially driven, allowing bidirectional current flow
in the outputs, thus providing up to 305¡ range of meter
deflection. Driving the coils differentially offers faster
response time, higher current capability, higher output
voltage swings, and reduced external component count.
The key advantage is a higher torque output for the
pointer.
The output angle, Q, is equal to the F/V gain multiplied
by the function generator gain:
where:
Q = AF/V ´ AFG,
AFG = 77¡/V (typ)
The relationship between input frequency and output
angle is:
Q = AFG ´ 2 ´ FREQ ´ CT ´ RT ´ (VREG Ð 0.7V)
or, Q = 970 ´ FREQ ´ CT ´ RT
The ripple voltage at the F/V converterÕs output is deter-
mined by the ratio of CT and C4 in the formula:
2. Select R3 and R4
Resistor R3 sets the output current from the voltage regu-
lator. The maximum output current from the voltage reg-
ulator is 10mA, R3 must ensure that the current does not
exceed this limit.
Choose R3 = 3.3k½
The charge current for CT is:
VREG Ð 0.7V
3.3k½
=
1.90mA
C1 must charge and discharge fully during each cycle of
the input signal. Time for one cycle at maximum frequen-
cy is 2.85ms. To ensure that CT is discharged, assume that
the (R3 + R4) CT time constant is less than 10% of the
minimum input frequency pulse width.
T = 285µs
Choose R4 = 1k½.
Charge time: T = R3 ´ CT = 3.3k½ ´ 0.0033µF = 10.9µs
Discharge time:T = (R3 + R4)CT = 4.3k½ ´ 0.0033µF = 14.2µs
3. Determine C4
C4 is selected to satisfy both the maximum allowable rip-
ple voltage and response time of the meter movement.
CT(VREG Ð 0.7V)
C4 = VRIPPLE(MAX)
ÆV =
CT(VREG Ð 0.7V)
C4
Ripple voltage on the F/V output causes pointer or nee-
dle flutter especially at low input frequencies.
The response time of the F/V is determined by the time
constant formed by RT and C4. Increasing the value of C4
will reduce the ripple on the F/V output but will also
increase the response time. An increase in response time
causes a very slow meter movement and may be unac-
ceptable for many applications.
With C4 = 0.47µF, the F/V ripple voltage is 44mV.
Figure 7 shows how the CS8191 and the CS8441 are used
to produce a Speedometer and Odometer circuit.
5
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| PDF Descargar | [ Datasheet CS8191XDWFR20.PDF ] | |
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