LTC6943

13

6943f

Battery Powered Relative Humidity Sensor Signal Conditioner

9

6943 TA17

+

–

A1

LT1006

4.7k

LT1004

1.2V

0.1

+9

1.8k*

90%

TRIM

10k

2.32k*

5%

TRIM

500Ω

100pF

LTC6943

0.1µF

22M

SENSOR

10pF

3

15

+9

+9

OUTPUT

0-1.00V =

0-100% RH

*

SENSOR

= 1% FILM RESISTOR

= POLYPROPYLENE

= PANAMETRICS TYPE RHS

= 76% 1.7pF/RH

RH%

CAPACITANCE

5

25

50

75

90

379.3pF

413.3pF

455.8pF

498.3pF

523.8pF

0.1

0.1

11

12

16

13

2

10

7

6

45

1

≤

≤

≤

500pF AT RH

SENSOR RESPONSE

TYPICAL APPLICATIO S

6943 TA20

5V

5V

+

–

A1

LTC1050

INTEGRATOR

–

+

C1

LT1671

RESET

COMPARATOR

300pF

300k*

4V

OUT

0% TO 100% RH =

0Hz TO 1kHz

5V

5V

Q

L

Q

= 1% METAL FILM RESISTOR

= WIMA, TYPE MKP-2

= PANAMETRICS MC-2

= 196.7pF

= 227.8pF

0.31pF/RH

*

†

SENSOR

0% RH

100% RH

1000pF

†

BAT85

Q1

VN2222L

562k*

4V

1k*

13.3k*

100k

RH = 25% TRIM

(204.5pF)

110k*

1N5712

200Ω

TO ALL 4V

POINTS

LT1634

4V

5V

20k

RH = 100% TRIM

(227.8pF)

SD

10k

6

11

7

12

9

10

14

15

3

4V

4V

4V

SENSOR

CHARGE

PUMP

LTC6943

1µF

0.1µF

1µF

4V

GND

LTC1799

CLOCK

OUT

80.6k*

10k

1N4148

125kHz

O1

+V

5V Powered, Frequency Output, Relative Humidity Sensor Signal Conditioner