Pin description – Rainbow Electronics MAX6645 User Manual

Page 4

MAX6643/MAX6644/MAX6645

Automatic PWM Fan-Speed Controllers with
Overtemperature Output

_______________________________________________________________________________________

Pin Description

PIN

MAX6643_A MAX6643_B

MAX6644_

MAX6645_

NAME

FUNCTION

1, 15

—

TH1, TH2

High-Temperature Threshold Inputs. Connect to V

, GND,

or leave unconnected to select the upper fan-control trip
temperature (T

HIGH

), in 5°C increments. See Table 1.

2, 3

—

TL2, TL1

Low-Temperature Threshold Inputs. Connect to V

, GND,

or leave unconnected to select the lower fan-control trip
temperature (T

LOW

), in 5°C increments. See Table 2.

FANFAIL

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.

TACHSET

FAN_IN_ Control Input. TACHSET controls what type of fan-
fail condition is being detected. Connect TACHSET to V

GND, or leave floating to set locked rotor, current sense, or
tachometer configurations (see Table 3).

—

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.

GND

Ground

—

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 .

Active-Low, Open-Drain Overtemperature Output. When OT
threshold is exceeded, OT pulls low.

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.