LM78 National Semiconductor, LM78 Datasheet - Page 10

• Manufacturer Part Number: LM78
• Description: Microprocessor System Hardware Monitor
• Manufacturer: National Semiconductor

www.national.com
Electrical Characteristics (Continued)
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is
functional, but do not guarantee specific performance limits. For guaranteed specifications and test conditions, see the Electrical Characteristics. The guaranteed
specifications apply only for the test conditions listed. Some performance characteristics may degrade when the device is not operated under the listed test
conditions.
Note 2: All voltages are measured with respect to GND, unless otherwise specified
Note 3: When the input voltage (V
The 20 mA maximum package input current rating limits the number of pins that can safely exceed the power supplies with an input current of 5 mA to four.
Note 4: The maximum power dissipation must be derated at elevated temperatures and is dictated by T
allowable power dissipation at any temperature is P
Note 5: The human body model is a 100 pF capacitor discharged through a 1.5 k
directly into each pin.
Note 6: See the section titled “Surface Mount” found in any post 1986 National Semiconductor Linear Data Book for other methods of soldering surface mount
devices.
Note 7: Each input and output is protected by a nominal 6.5V breakdown voltage zener diode to GND; as shown below, input voltage magnitude up to 0.3V above
V
can occur if these diodes are forward biased by more than 50 mV. As an example, if V
conversions.
An x indicates that the diode exists.
Note 8: Typicals are at T
Note 9: Limits are guaranteed to National’s AOQL (Average Outgoing Quality Level).
Note 10: TUE (Total Unadjusted Error) includes Offset, Gain and Linearity errors of the ADC and any error introduced by the amplifiers as shown in the circuit of
Figure 13 .
Note 11: Total Monitoring Cycle Time includes temperature conversion, 7 analog input voltage conversions and 3 tachometer readings. Each temperature and input
voltage conversion takes 100 ms typical and 112 ms maximum. Fan tachometer readings take 20 ms typical, at 4400 rpm, and 200 ms max.
Note 12: The total fan count is based on 2 pulses per revolution of the fan tachometer output.
Note 13: Timing specifications are tested at the TTL logic levels, V
to 1.4V.
IORD
IOWR
SYSCLK
D0–D7
SMI__IN
Chassis Intrusion
Power Switch
Bypass
−IN6
FB6
FB5
−IN5
IN4–IN0
VID3–VID0
CC
Pin Name
or 0.3V below GND will not damage the LM78. There are parasitic diodes that exist between the inputs and the power supply rails. Errors in the ADC conversion
Pin Name
D1
x
x
x
x
J
=T
A
D1
x
x
=25˚C and represent most likely parametric norm.
D2
x
x
x
x
x
x
IN
) at any pin exceeds the power supplies (V
D2
x
x
x
D3
x
x
x
x
x
x
D3
x
x
x
x
x
x
x
D
FIGURE 4. ESD Protection Input Structure
= (T
J
max−T
A
)/
IL
=0.4V for a falling edge and V
JA
.
IN
10
<
(GNDD or GNDA) or V
resistor into each pin. The machine model is a 200 pF capacitor discharged
FAN1–FAN3
SCL
SDA
RESET
NTEST
BTI
NMI/IRQ
SMI
A0–A2
CS
Pin Name
CC
Pin Name
is 4.50 V
DS012873-7
IH
=2.4V for a rising edge. TRI-STATE output voltage is forced
DC
J
max,
IN
, input voltage must be
>
D1
x
x
V
CC
JA
), the current at that pin should be limited to 5 mA.
and the ambient temperature, T
D1
x
D2
x
x
D2
x
x
x
D3
x
x
x
x
x
D3
x
x
x
x
x
4.55 V
DC
, to ensure accurate
A
. The maximum