MAX6650 View Datasheet(PDF) - Maxim Integrated
Part Name
Description
Manufacturer
MAX6650 Datasheet PDF : 25 Pages
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MAX6650/MAX6651
Fan-Speed Regulators and Monitors
with SMBus/I2C-Compatible Interface
Table 5. GPIO Definition Register
BIT
POR
(DEFAULT)
STATE
MAX6650
PIN
MAX6651
PIN
7
1
N/A
GPIO4
(must be 1)
6
1
N/A
(must be 1)
GPIO3
5:4
11
N/A
(must be 11)
GPIO2
3:2
11
GPIO1
GPIO1
1:0
11
GPIO0
GPIO0
STATE
FUNCTION
0
GPIO4 outputs a logic-low level.
1
GPIO4 outputs a logic-high level or serves as an input.
0
GPIO3 outputs a logic-low level.
1
GPIO3 outputs a logic-high level or serves as an input.
00
GPIO2 serves as an external clock input.
01
GPIO2 serves as an internal clock output.
10
GPIO2 outputs a logic-low level.
11
GPIO2 outputs a logic-high level or serves as an input.
00
GPIO1 outputs a logic-high level or serves as an input.
01
GPIO1 serves as a FULL ON input.
10
GPIO1 outputs a logic-low level.
11
GPIO1 outputs a logic-high level or serves as an input.
00
GPIO0 outputs a logic-high level or serves as an input.
01
GPIO0 serves as an ALERT output.
10
GPIO0 outputs a logic-low level.
11
GPIO0 outputs a logic-high level or serves as an input.
Table 6. GPIO Status Register
BIT
7 (MSB) to 5
4
3
2
1
0 (LSB)
NAME
Always 0
GPIO4 (MAX6651 only)
GPIO3 (MAX6651 only)
GPIO2 (MAX6651 only)
GPIO1
GPIO0
POR
(DEFAULT
STATE)
0
1
1
1
1
1
Alarm Status Register if the condition that caused the
alarm is removed.
Tachometer
The Tachometer Count Registers record the number of
pulses on the corresponding tachometer input during the
period defined by the Tachometer Count-Time Register.
The MAX6651 contains three additional tachometer
inputs, which may be used to monitor additional fans. For
accurate control of multiple fans, use identical fans.
The Tachometer Count-Time Register sets the integration
time over which the MAX6650/MAX6651 count tachome-
ter pulses. The devices can count up to 255 (FFh) pulses
during the selected count time. If more than 255 pulses
occur, the IC sets the overflow alarm and the Tachometer
Count Register reports the maximum value of 255. Set
the time register so the count register will not overflow
under worst-case conditions (maximum fan speed) while
maximizing resolution. Calculate the maximum measur-
able fan speed and minimum resolution with the following
equations:
Max Fan Speed (in RPS) = 255 / (2 x tCOUNT)
Min Resolution (in RPS) = 1 / (2 x tCOUNT)
where tCOUNT is the tachometer count time; 1kHz is the
maximum allowable tachometer input frequency for the
MAX6650/MAX6651.
Maxim Integrated
11
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