Datasheet CS4121ENF16, CS4121EDWFR20, CS4121EDWF20 Datasheet (Cherry Semiconductor)

1

Features

■

Direct Sensor Input

■

High Torque Output

■

Low Pointer Flutter

■

High Input Impedance

■ Overvoltage Protection

■ Accurate to 8V

Functional to 6.5V (typ)

Package Options

16 Lead PDIP

(internally fused leads)

20 Lead SOIC

(internally fused leads)

CS4121

Low Voltage Precision Air-Core

Tach/Speedo Driver

1

CP+

2

3

4

5

6

7

8

SQ

OUT

FREQ

IN

Gnd

Gnd

COS+

COS-

V

CC

16

15

14

13

12

11

10

9

CP-

F/V

OUT

V

REG

Gnd

Gnd

SINE+

SINE-

BIAS

1

CP+

2

3

4

5

6

7

8

SQ

OUT

FREQ

IN

Gnd

Gnd

Gnd

Gnd

COS+

16

15

14

13

12

11

10

CP-

F/V

OUT

V

REG

Gnd

Gnd

Gnd

Gnd

SIN+

9

COS- SIN-

17

18

V

CC

BIAS

19

20

CS4121

Description

The CS4121 is specifically designed
for use with air-core meter move­ments. The IC provides all the func­tions necessary for an analog
tachometer or speedometer. The
CS4121 takes a speed sensor input
and generates sine and cosine relat­ed output signals to differentially
drive an air-core meter.

Many enhancements have been
added over industry standard
tachometer drivers such as the
CS289 or LM1819. The output uti­lizes differential drivers which elim-

inates the need for a zener reference
and offers more torque. The device
withstands 60V transients which
decreases the protection circuitry
required. The device is also more
precise than existing devices allow­ing for fewer trims and for use in a
speedometer.

The CS4121 is compatible with the
CS8190, and provides higher accu­racy at a lower supply voltage (8.0V
min. as opposed to 8.5V). It is func­tionally operational to 6.5V.

Block Diagram

Absolute Maximum Ratings

Supply Voltage (<100ms pulse transient)..........................................VCC= 60V

(continuous)..............................................................VCC= 24V

Operating Temperature .............................................................Ð40¡C to +105¡C

Storage Temperature..................................................................Ð40¡C to +165¡C

Junction Temperature .................................................................Ð40¡C to+150¡C

ESD (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

Cherry Semiconductor Corporation

2000 South County Trail, East Greenwich, RI 02818

Tel: [phone] Fax: [phone]

Email: [e-mail]

Web Site: www.cherry-semi.com

A Company

¨

Rev 12/4/96

Voltage

Regulator

V

REG

7.0V

+

Ð

Ð

+

Output

+

Ð

SINE

F/V

CP-

V

REG

Gnd

Gnd

SINE+

SINE-

OUT

BIAS

SQ

FREQ

COS

COS

CP+

OUT

Gnd

Gnd

V

IN

+

CC

-

Charge Pump

Input

Comp.

+

Ð

Ð

+

COS

Output

+

Ð

Func.

Gen.

High Voltage

Protection

2

Electrical Characteristics: -40¡C ² TA² 85¡C, 8.0V ² VCC² 16V unless otherwise specified.

PARAMETER TEST CONDITIONS MIN TYP MAX UNIT

CS4121

■ Supply Voltage Section

ICCSupply Current VCC= 16V, -40¡C, No Load 50 125 mA
VCCNormal Operation Range

8.0 13.1 16.0 V

■ Input Comparator Section

Positive Input Threshold 1.0 2.0 3.0 V
Input Hysteresis 200 500 mV
Input Bias Current * 0V ² VIN² 8V -10 -80 µA
Input Frequency Range 0 20 kHz
Input Voltage Range in series with 1k½ -1 V

CC

V

Output V

SAT

ICC= 10mA 0.15 0.40 V
Output Leakage VCC= 7V 10 µA
Logic 0 Input Voltage 1 V

*Note: Input is clamped by an internal 12V Zener.

■ Voltage Regulator Section

Output Voltage 6.25 7.00 7.50 V
Output Load Current 10 mA
Output Load Regulation 0 to 10 mA 10 50 mV
Output Line Regulation 8.0V ² VCC² 16V 20 150 mV
Power Supply Rejection VCC= 13.1V, 1VP/P1kHz 34 46 dB

■ Charge Pump Section

Inverting Input Voltage 1.5 2.0 2.5 V
Input Bias Current 40 150 nA
Vbias Input Voltage 1.5 2.0 2.5 V
Non Invert. Input Voltage IIN= 1mA 0.7 1.1 V
Linearity* @ 0, 87.5, 175, 262.5, + 350Hz -0.10 0.28 +0.70 %
F/V

OUT

Gain @ 350Hz, CT = 0.0033µF, RT = 243k½ 7 10 13 mV/Hz
Norton Gain, Positive IIN= 15µA 0.9 1.0 1.1 I/I
Norton Gain, Negative IIN= 15µA 0.9 1.0 1.1 I/I

*Note: Applies to % of full scale (270¡).

■ Function Generator Section: -40¡C ² T

A

² 85¡C, VCC= 13.1V unless otherwise noted.

Differential Drive Voltage 8.0V ² VCC² 16V 5.5 6.5 7.5 V

(V

COS

+ - V

COS

-) Q = 0¡

Differential Drive Voltage 8.0V ² VCC² 16V 5.5 6.5 7.5 V

(V

SIN

+ - V

SIN

-) Q = 90¡

Differential Drive Voltage 8.0V ² VCC² 16V -7.5 -6.5 -5.5 V

(V

COS

+ - V

COS

-) Q = 180¡

Differential Drive Voltage 8.0V ² VCC² 16V -7.5 -6.5 -5.5 V

(V

SIN

+ - V

SIN

-) Q = 270¡
Differential Drive Current 8.0V ² VCC² 16V, TA=25¡C 33 42 mA
Zero Hertz Output Angle -1.5 0.0 1.5 deg
Function Generator Error * VCC= 13.1V, TA=25¡C -2 0 +2 deg

Reference Figures 1,2,3,4 Q = 0¡ to 305¡

*Note: Deviation from nominal per Table 1 after calibration at 0¡ and 270¡.

3

PACKAGE LEAD # LEAD SYMBOL FUNCTION

CS4121

Electrical Characteristics: continued

PARAMETER TEST CONDITIONS MIN TYP MAX UNIT

Package Lead Description

Typical Performance Characteristics

0 45 90 135 180 225 270 315

Output Voltage (V)

Degrees of Deflection (°)

7

6

5

4

3
2

1

0

-1

-2

-3

-4

-5

-6

-7

COS

SIN

045

90

135 180 225 270 315

F/V Output (V)

Frequency/Output Angle (°)

7

6

5

4

3

2

1

0

Figure 2: Charge Pump Output Voltage vs Output Angle

Figure 1: Function Generator Output Voltage

vs Degrees of Deflection

F/V

OUT

= 2.0V + 2 FREQ ´ CT´ RT´ (V

REG

- 0.7)

■ Function Generator Section: continued

Function Generator Error 13.1V ² V

CC

² 16V, TA=25¡C -2.5 0 +2.5 deg

Function Generator Error 13.1V ² V

CC

² 11V, TA=25¡C -1 0 +1 deg

Function Generator Error 13.1V ² V

CC

² 8V, TA=25¡C -3 0 +3 deg

Function Generator Error 25¡C ² T

A

² 85¡C -3 0 +3 deg

Function Generator Error 25¡C ² T

A

² 105¡C -5.5 0 +5.5 deg

Function Generator Error Ð40¡C ² T

A

² 25¡C -3 0 +3 deg

Function Generator Gain T

A

= 25¡C Q vs F/V

OUT

60 77 95 ¡/V

16L PDIP* 20L SO*

1 1 CP+ Positive input to charge pump.

22SQ

OUT

Buffered square wave output signal.

3 3 FREQ

IN

Speed or rpm input signal.

4, 5, 12, 13 4-7, 14-17 Gnd Ground Connections.

6 8 COS+ Positive cosine output signal.

7 9 COS- Negative cosine output signal.

810VCCIgnition or battery supply voltage.

9 11 BIAS Test point or zero adjustment.

10 12 SIN- Negative sine output signal.

11 13 SIN+ Positive sine output signal.

14 18 V

REG

Voltage regulator output.

15 19 F/V

OUT

Output voltage proportional to input signal frequency.

16 20 CP- Negative input to charge pump.

*Internally Fused Leads

4

00
1 1.09
2 2.19
3 3.29
4 4.38
5 5.47
6 6.56
7 7.64
8 8.72

9 9.78
10 10.84
11 11.90
12 12.94
13 13.97
14 14.99
15 16.00
16 17.00

17 17.98
18 18.96
19 19.92
20 20.86
21 21.79
22 22.71
23 23.61
24 24.50
25 25.37
26 26.23
27 27.07
28 27.79
29 28.73
30 29.56
31 30.39
32 31.24
33 32.12

34 33.04
35 34.00
36 35.00
37 36.04
38 37.11
39 38.21
40 39.32
41 40.45
42 41.59
43 42.73
44 43.88
45 45.00
50 50.68
55 56.00
60 60.44
65 64.63
70 69.14

75 74.00
80 79.16
85 84.53
90 90.00

95 95.47
100 100.84
105 106.00
110 110.86
115 115.37
120 119.56
125 124.00
130 129.32
135 135.00
140 140.68
145 146.00
150 150.44
155 154.63

160 159.14
165 164.00
170 169.16
175 174.33
180 180.00
185 185.47
190 190.84
195 196.00
200 200.86
205 205.37
210 209.56
215 214.00
220 219.32
225 225.00
230 230.58
235 236.00
240 240.44

245 244.63
250 249.14
255 254.00
260 259.16
265 264.53
270 270.00
275 275.47
280 280.84
285 286.00
290 290.86
295 295.37
300 299.21
305 303.02

Ideal Q Nominal Ideal Q Nominal Ideal Q Nominal Ideal Q Nominal Ideal Q Nominal Ideal Q Nominal

Degrees Q Degrees Degrees Q Degrees Degrees Q Degrees Degrees Q Degrees Degrees Q Degrees Degrees Q Degrees

Typical Performance Characteristics: continued

CS4121

Nominal Angle vs. Ideal Angle (After calibrating at 180¡)

+7V

Ð7V

(V

COS+

) - (V

COS-

)

7V

Angle

-7V

Q

(V

SINE+

) - (V

SINE-

)

]

V

SIN+

Ð V

SIN-

V

COS+

Ð V

COS-

Q = ARCTAN

[

-1.50

Deviation (°)

0 45 90 135 180 225 270 315

-1.25

-1.00

-0.75

-0.50

-0.25

0.00

0.25

0.50

0.75

1.00

1.25

1.50

Theoretical Angle (°)

Figure 4: Nominal Output Deviation

Figure 3: Output Angle in Polar Form

Ideal Angle (Degrees)

Nominal Angle (Degrees)

0

5

10

15

20

25

30

35

40

45

1 5 9 13 17 21 25 29 33 37 41 45

Ideal Degrees

Nominal Degrees

Table 1: Function Generator Output Nominal Angle vs. Ideal Angle (After calibrating at 270¡)

Note: Temperature, voltage and nonlinearity not included.

Note: Temperature, voltage and nonlinearity not included.

5

CS4121

The CS4121 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 conver­sion, 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 FREQINlead, this is the
input to a high impedance comparator with a typical pos­itive input threshold of 2.0V and typical hysteresis of

0.5V. The output of the comparator, SQ

OUT

, 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 accumulat­ed on CTis mirrored to C4 by the Norton Amplifier cir­cuit comprising of Q1, Q2 and Q3. The charge pump out­put voltage, F/V

OUT

, ranges from 2V to 6.3V depending
on the input signal frequency and the gain of the charge
pump according to the formula:

F/V

OUT

= 2.0V + 2 ´ FREQ ´ CT´ RT´ (V

REG

Ð 0.7V)

RTis 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 genera­tor 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:

Q = A

F/V

´ AFG,

where:

AFG= 77¡/V(typ)
The relationship between input frequency and output

angle is:

Q = AFG´ 2 ´ FREQ ´ CT´ RT´ (V

REG

Ð 0.7V)

or, Q = 970 ´ FREQ ´ CT´ R

T

The ripple voltage at the F/V converterÕs output is deter­mined by the ratio of CTand C4 in the formula:

ÆV =

Ripple voltage on the F/V output causes pointer or nee­dle flutter especially at low input frequencies.

The response time of the F/V is determined by the time
constant formed by RTand 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 unac­ceptable for many applications.

Design Example

Maximum meter Deflection = 270¡
Maximum Input Frequency = 350Hz

1. Select RTand C

T

Q = A

GEN

´ Æ

F/V

Æ

F/V

= 2 ´ FREQ ´ CT´ RT´ (V

REG

Ð 0.7V)

Q = 970 ´ FREQ ´ CT´ R

T

Let CT= 0.0033µF, Find R

T

RT=

RT= 243k½

RTshould be a 250k½ potentiometer to trim out any inac­curacies due to IC tolerances or meter movement pointer
placement.

2. Select R3 and R4

Resistor R3 sets the output current from the voltage regu­lator. The maximum output current from the voltage reg­ulator is 10mA R3 must ensure that the current does not
exceed this limit.

Choose R3 = 3.3k½

The charge current for CTis

= 1.90mA

C1 must charge and discharge fully during each cycle of
the input signal. Time for one cycle at maximum frequen­cy is 2.85ms. To ensure that CTis discharged, assume that
the (R3 + R4) CTtime constant is less than 10% of the
minimum input frequency pulse width.

T = 285µs

Choose R4 = 1k½.

Charge time: T = R3 ´ C

T

= 3.3k½ ´ 0.0033µF = 10.9µs

Discharge time:T = (R3 + R4)C

T

= 4.3k½ ´ 0.0033µF = 14.2µs

3. Determine C4

C4 is selected to satisfy both the maximum allowable rip­ple voltage and response time of the meter movement.

C4 =

With C4 = 0.47µF, the F/V ripple voltage is 44mV.
Figure 7 shows how the CS4121 and the CS-8441 are used

to produce a Speedometer and Odometer circuit.

CT(V

REG

Ð 0.7V)

V

RIPPLE(MAX)

V

REG

Ð 0.7V

3.3k½

270¡

970 ´ 350Hz ´ 0.0033µF

C

T(VREG

Ð 0.7V)

C4

Circuit Description and Application Notes

6

CS4121

Circuit Description and Application Notes: continued

+

Ð

R

T

C4

CPÐ

+

Ð

F/V

OUT

F to V

2.0V

Q2

Q1

Q3

0.25V

CP+

R4C

T

VC(t)

+Ð

R3

V

REG

SQ

OUT

Q

SQUARE

2.0V

FREQ

IN

Figure 5A: Partial Schematic of Input and Charge Pump

Figure 5B: Timing Diagram of FREQINand I

CP

T

PW T-PW

FREQ

IN

SQ

OUT

I

CP+

V

CP+

0

0

0

V

CC

V

REG

7

Speedometer/Odometer or Tachometer Application

R1 - 3.9, 500mW
R2 - 10k½
R3 - 3k½
R4 - 1k½
R

T

- Trim Resistor +/- 20 PPM/¡C 243k½

C1 - 0.1µF
C3 - 0.1µF
C4 - 0.47µF

C

T

- 0.0033µF, +/- 30 PPM/¡C

D1 - 1A, 600 PIV
D2 - 50V, 500mW Zener

Note 1: For 58% Speed Input T

MAX

² 5/f

MAX

where

T

MAX

= CT(R3+R4)

f

MAX

= maximum speed input frequency

Note 1: The product of C

T

and RThave a direct effect on

gain and therefore directly affect temperature compensation

Note 2: C

T

Range; 20pF to .2µF

Note 3: R

T

Range; 100k½ to 500k½

Note 4: The IC must be protected from transients above 60V and

reverse battery conditions

Note 5: Additional filtering on FREQ

IN

lead may be required

1

CP+

2

3

4

5

6

7

8

SQ

OUT

FREQ

IN

Gnd

Gnd

COS+

COS-

V

CC

16

15

14

13

12

11

10

9

CP-

F/V

OUT

V

REG

Gnd

Gnd

SINE+

SINE-

BIAS

CS4121

C

T

R3

C3

C1D2

R1D1

+

C4

R

T

COSINE SINE

Air Core

Gauge

200W

Speedometer

Gnd

Battery

Speedo

Input

R2

R4

1

CS8441

C2

Air Core

Stepper Motor

200W

Odometer

CP+

1

CP+

2

3

4

5

6

7

8

SQ

OUT

FREQ

IN

Gnd

Gnd

COS+

COS-

V

CC

16

15

14

13

12

11

10

9

CP-

F/V

OUT

V

REG

Gnd

Gnd

SINE+

SINE-

BIAS

CS4121

C

T

R3

C3

C1D2

R1D1

+

C4

R

T

COSINE SINE

Air Core

Gauge

200W

Speedometer

Gnd

Battery

Speedo

Input

R2

R4

CP+

Figure 6

Figure 7

CS4121

D

Lead Count Metric English

Max Min Max Min
16L PDIP* 19.69 18.67 .775 .735
20L SOIC* 13.00 12.60 .512 .496

8

Ordering Information

Rev. 12/4/96

Part Number Description

CS4121ENF16 16L PDIP (internally fused leads)
CS4121EDWF20 20L SOIC (internally fused leads)
CS4121EDWFR20 20L SOIC (internally fused leads)

(tape & reel)

Thermal Data 16L PDIP* 20L SOIC*

R

QJC

typ 15 9 ûC/W

R

QJA

typ 50 55 ûC/W

Package Specification

PACKAGE DIMENSIONS IN mm (INCHES)

PACKAGE THERMAL DATA

CS4121

© 1999 Cherry Semiconductor Corporation

Cherry Semiconductor Corporation reserves the
right to make changes to the specifications without
notice. Please contact Cherry Semiconductor
Corporation for the latest available information.

1.27 (.050) BSC

7.60 (.299)

7.40 (.291)

10.65 (.419)

10.00 (.394)

D

0.32 (.013)

0.23 (.009)

1.27 (.050)

0.40 (.016)

REF: JEDEC MS-013

2.49 (.098)

2.24 (.088)

0.51 (.020)

0.33 (.013)

2.65 (.104)

2.35 (.093)

0.30 (.012)

0.10 (.004)

Surface Mount Wide Body (DW); 300 mil wide

Plastic DIP (N); 300 mil wide

0.39 (.015)
MIN.

2.54 (.100) BSC

1.77 (.070)

1.14 (.045)

D

Some 8 and 16 lead
packages may have
1/2 lead at the end
of the package.
All specs are the same.

.203 (.008)

.356 (.014)

REF: JEDEC MS-001

3.68 (.145)

2.92 (.115)

8.26 (.325)

7.62 (.300)

7.11 (.280)

6.10 (.240)

.356 (.014)

.558 (.022)

*Internally Fused Leads