LM63

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SNAS190E – SEPTEMBER 2002 – REVISED MAY 2013

Table 7. Tachometer Count And Limit Registers

ADDRESS

READ/

POR

BITS

NAME

DESCRIPTION

HEX

WRITE

VALUE

47HEX TACHOMETER COUNT (MSB) and 46HEX TACHOMETER COUNT (LSB) REGISTERS (16 bits: Read LSB first to lock MSB and

ensure MSB and LSB are from the same reading)

Tachometer

These registers contain the current 16-bit Tachometer

47

Read Only

7:0

N/A

Count (MSB)

Count, representing the period of time between tach pulses.

Note that the 16-bit tachometer MSB and LSB are reversed

Tachometer

Read Only

7:2

N/A

from the 16-bit temperature readings.

Count (LSB)

Bits

Edges Used

Tach_Count_Multiple

00:

Reserved - do not use

01:

2

4

Tachometer

10:

3

2

46

Read Only

1:0

00

Edge Count

11:

5

1

Note: If PWM_Clock_Select = 360 kHz, then

Tach_Count_Multiple = 1 regardless of the setting of these

bits.

49HEX TACHOMETER LIMIT (MSB) and 48HEX TACHOMETER LIMIT (LSB) REGISTERS

Tachometer

These registers contain the current 16-bit Tachometer

49

R/W

7:0

0xFF

Limit MSB)

Count, representing the period of time between tach pulses.

Fan RPM = (f * 5,400,000) / (Tachometer Count), where f =

1 for 2 pulses/rev fan; f = 2 for 1 pulse/rev fan; and f = 2/3

for 3 pulses/rev fan. See the APPLICATION NOTES section

Tachometer

R/W

7:2

0xFF

at the end of this datasheet for more tachometer

Limit (LSB)

48

information. Note that the 16-bit tachometer MSB and LSB

are reversed from the 16 bit temperature readings.

R/W

1:0

[Reserved]

Not Used.

Table 8. Local Temperature And Local High Setpoint Registers

ADDRESS

READ/

POR

BITS

NAME

DESCRIPTION

HEX

WRITE

VALUE

00HEX LOCAL TEMPERATURE REGISTER (8-bits)

Local Temperature

00

Read Only

7:0

N/A

8-bit integer representing the temperature of the LM63 die.

Reading (8-bit)

05 (0B)HEX LOCAL HIGH SETPOINT REGISTER (8-bits)

05

R/W

7:0

0x46 (70°) Local HIGH Setpoint High Setpoint for the internal diode.

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