Datasheet

MAX6643/MAX6644/MAX6645
Automatic PWM Fan-Speed Controllers with
Overtemperature Output
4 _______________________________________________________________________________________
Pin Description
PIN
MAX6643 MAX6644 MAX6645
NAME FUNCTION
1, 15 1, 15 — TH1, TH2
High-Temperature Threshold Inputs. Connect to V
DD
, GND, or
leave unconnected to select the upper fan-control trip
temperature (T
HIGH
), in 5°C increments. See Table 1.
2, 3 2, 3 — TL2, TL1
Low-Temperature Threshold Inputs. Connect to V
DD
, GND, or
leave unconnected to select the lower fan-control trip
temperature (T
LOW
), in 5°C increments. See Table 2.
441FANFAIL
Fan-Fail Alarm Output. FANFAIL is an active-low, open-drain
output. If the FAN_IN_ detects a fan failure, the FANFAIL output
asserts low.
5 5 2 TACHSET
FAN_IN_ Control Input. TACHSET controls what type of fan-fail
condition is being detected. Connect TACHSET to V
DD
, GND,
or leave floating to set locked rotor, current sense, or
tachometer configurations (see Table 3).
6 — — FULLSPD
Active-High Logic Input. When pulled high, the fan runs at
100% duty cycle.
———FULLSPD
Active-Low Logic Input. When pulled low, the fan runs at 100%
duty cycle.
7 7 4 GND Ground
8 — — DXP
— 6, 8 3, 5 DXP2, DXP1
C om b i ned C ur r ent S our ce and A/D P osi ti ve Inp ut for Rem ote
D i od e. C onnect to anod e of r em ote d i od e- connected
tem p er atur e- sensi ng tr ansi stor . C onnect to G N D i f no r em ote
d i od e i s used . P l ace a 2200p F cap aci tor b etw een D X P _ and
G N D for noi se fi l ter i ng .
996OT
Active-Low, Open-Drain Overtemperature Output. When OT
threshold is exceeded, OT pulls low.
10, 11 10, 11 7, 8
FAN_IN2,
FAN_IN1
Fan- S ense Inp ut. FAN _IN _ can b e confi g ur ed to m oni tor ei ther a
fan’ s l og i c- l evel l ocked - r otor outp ut, tachom eter outp ut, or sense-
r esi stor w avefor m to d etect fan fai l ur e. The M AX 6643’ s FAN _IN _
i np ut can m oni tor onl y tachom eter si g nal s. The M AX 6644 and the
M AX 6645 can m oni tor any one of the thr ee si g nal typ es as
confi g ur ed usi ng the TAC H S E T i np ut.