THMC50

REMOTE/LOCAL TEMPERATURE MONITOR AND

FAN CONTROLLER WITH SMBus INTERFACE

SLIS090 – JULY 1999

14

POST OFFICE BOX 655303

PRINCIPLES OF OPERATION

analog output - FAN_SPD (continued)

FAN_SPD/NTEST_IN

+12 V

R1

100 k

Ω

R2

100 k

Ω

Q1/Q2

MBT3904

DUAL

Q3

IRF9620

R3

3.9 k

Ω

R4

1 k

Ω

R5

5 k

Ω

Figure 9. External Fan Drive Circuit Using Discrete Components With P-Channel FET, Single Supply

+12 V

FAN_SPD/NTEST_IN

–12 V

R2

100 k

Ω

Q1/Q2

MBT3904

DUAL

R1

4.7 k

Ω

Q3

IRF9620

R3

39 k

Ω

R4

10 k

Ω

Figure 10. External Fan Drive Circuit Using Discrete Components With P-Channel FET, Dual Supply

+12 V

FAN_SPD/NTEST_IN

R1

100 k

Ω

R2

100 k

Ω

Q3

BC556

2N3906

R5

100

Ω

Q1/Q2

MBT3904

DUAL

Q4

BD132

TIP32A

R3

3.9 k

Ω

R4

1 k

Ω

R6

5 k

Ω

Figure 11. External Fan Drive Circuit Using Discrete Components and

PNP Output Transistor, Single Supply