CS8190EDWFR20 Просмотр технического описания (PDF) - Cherry semiconductor

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CS8190EDWFR20

Precision Air-Core Tach/Speedo Driver with Return to Zero

Cherry semiconductor 

Circuit Description and Application Notes: continued

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)

With C4 = 0.47µF, the F/V ripple voltage is 44mV.

The last component to be selected is the return to zero

capacitor C2. This is selected by increasing the input sig-

nal frequency to its maximum so the pointer is at its max-

imum deflection and removing the power from the cir-

cuit. C2 should be large enough to ensure that the pointer

always returns to the 0¡ position rather than 360¡ under

all operating conditions.

Figure 7 shows how the CS8190 and the CS8441 are used

to produce a Speedometer and Odometer circuit.

VREG

FREQIN

R3

SQOUT

VC(t)

+Ð

CT R4

+

Ð

QSQUARE

2.0V

0.25V

CP+

Q1

2.0V

Q3 CPÐ

Q2

+

Ð

RT

F/VOUT

F to V

C4

Figure 5A: Partial Schematic of Input and Charge Pump

PW

VCC

FREQIN 0

SQOUT

0

VREG

ICP+

VCP+

0

T

T-PW

Figure 5B: Timing Diagram of FREQIN and ICP

6

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