Rainbow Electronics MAX6640 - Manual (Page 5)

MAX6640
2-Channel Temperature Monitor with Dual
Automatic PWM Fan-Speed Controller
_______________________________________________________________________________________ 5
PIN
TQFN QSOP
NAME FUNCTION
1, 15 3, 1
PWM2,
PWM1
Open-Drain Output to Power Transistor Driving Fan. Connect to the gate of a MOSFET or base of a
bipolar transistor. PWM_ requires a pullup resistor. The pullup resistor can be connected to a supply
voltage as high as 13.5V, regardless of the MAX6640’s supply voltage.
2, 16 4, 2
TACH2,
TACH1
Tachometer Inputs. Connect to the tachometer output of the fan. TACH_ requires a pullup resistor. The
pullup resistor can be connected to a supply voltage as high as 13.5V, regardless of the MAX6640’s
supply voltage.
3 5 FANFAIL Active-Low, Open-Drain, Fan-Failure Output. Open circuit when V
CC
= 0.
4 6 THERM
Active-Low, Open-Drain Thermal Alarm Output. Typically used for clock throttling. Open circuit when
V
CC
= 0.
5 7 OT
Active-Low, Open-Drain Overtemperature Output. Typically used for system shutdown or clock
throttling. Can be pulled up to 5.5V regardless of V
CC . Open circuit when V CC = 0.
6 8 V CC Power-Supply Input. 3.3V nominal. Bypass V CC to GND with a 0.1µF capacitor.
7 10 GND Ground. Connect to a clean ground reference.
8, 10 9, 12
DXP1,
DXP2
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 . D o not l eave fl oati ng ; connect to D X N 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 D X N for noi se fi l ter i ng .
9 11 DXN Connect Cathode of the Remote-Diode-Connected Transistor to DXN
11 13 V CC Connect to V CC
12 14 ALERT Active-Low, Open-Drain SMBus Alert Output
13 16 SCL SMBus Serial-Clock Input. Can be pulled up to 5.5V regardless of V CC . Open circuit when V CC = 0.
14 15 SDA
SMBus Serial-Data Input/Output, Open Drain. Can be pulled up to 5.5V regardless of V CC . Open
circuit when V CC = 0.
Pin Description
Typical Operating Characteristics (continued)
(V
CC
= 3.3V, T
A
= +25°C)
PWMOUT FREQUENCY
vs. DIE TEMPERATURE
MAX6640 toc10
TEMPERATURE (°C)
PWMOUT FREQUENCY (Hz)
85 60 35 10 -15
31
32
33
34
35
30
-40 110
PWMOUT FREQUENCY
vs. SUPPLY VOLTAGE
MAX6640 toc11
SUPPLY VOLTAGE (V)
PWMOUT FREQUENCY (Hz)
5.0 4.5 4.0 3.5
31
32
33
34
35
30
3.0 5.5