LM81CIMTX-3 National Semiconductor, LM81CIMTX-3 Datasheet - Page 17

• Manufacturer Part Number: LM81CIMTX-3
• Manufacturer: National Semiconductor

Specifications of LM81CIMTX-3

• Monitored Voltage 1 (typ): 2.5/3.3/5/12V
• Battery Backup Switching: No
• Watchdog Timer: Yes
• Chip Enable Signals: No
• Manual Reset: No
• Package Type: TSSOP
• Operating Supply Voltage (min): 2.8V
• Operating Supply Voltage (max): 3.8V
• Operating Temp Range: -40C to 125C
• Operating Temperature Classification: Automotive
• Power Fail Detection: No
• Mounting: Surface Mount
• Pin Count: 24
• Lead Free Status / Rohs Status: Not Compliant

Divide by 1
Divide by 2
Divide by 4
Divide by 8
Mode Select
Functional Description
Counts are based on 2 pulses per revolution tachometer outputs.
(c) Fan with Tach Pull-Up to +12V and Diode Clamp
RPM
4400
3080
2640
(a) Fan with Tach Pull-Up to +5V
Nominal
RPM
8800
4400
2200
1100
Time per Revolution
13.64 ms
19.48 ms
22.73 ms
Time per Revolution
(Continued)
13.64 ms
27.27 ms
54.54 ms
6.82 ms
FIGURE 7. Alternatives for Fan Inputs
DS100072-12
DS100072-14
Given Speed in Decimal
(d) Fan with Strong Tach Pull-Up or Totem Pole Output
17
Counts for “Divide by 2”
(b) Fan with Tach Pull-Up to +12V, or Totem-Pole
Counts for the
(Default) in Decimal
(maximum counts)
153
153
153
153
153 counts
219 counts
255 counts
Output and Resistor Attenuator
and Diode Clamp
RPM
6160
3080
1540
70%
770
Time per Revolution
Typical RPM
Comments
for 70% RPM
70% RPM
60% RPM
19.48 ms
38.96 ms
77.92 ms
DS100072-15
9.74 ms
DS100072-13
www.national.com