LM81BIMT-3/NOPB National Semiconductor, LM81BIMT-3/NOPB Datasheet - Page 17

• Manufacturer Part Number: LM81BIMT-3/NOPB
• Description: IC MONITOR SYS HARDWARE 24TSSOP
• Manufacturer: National Semiconductor

Specifications of LM81BIMT-3/NOPB

• Function: Hardware Monitor
• Topology: ADC (Sigma Delta), Comparator, Fan Speed Control, Register Bank
• Sensor Type: External & Internal
• Sensing Temperature: -40°C ~ 125°C, External Sensor
• Output Type: SMBus™
• Output Alarm: No
• Output Fan: No
• Voltage - Supply: 2.8 V ~ 3.8 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 24-TSSOP
• Monitored Voltage: 2.5 V , 3.3 V , 5 V , 12 V
• Manual Reset: Not Resettable
• Watchdog: Watchdog
• Battery Backup Switching: No
• Supply Voltage (max): 3.8 V
• Supply Voltage (min): 2.8 V
• Supply Current (typ): 400 uA (Typ)
• Maximum Operating Temperature: + 125 C
• Minimum Operating Temperature: - 40 C
• Power Fail Detection: No
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: *LM81BIMT-3; *LM81BIMT-3/NOPB; LM81BIMT-3

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
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