MAX6650EUB+T Maxim Integrated Products, MAX6650EUB+T Datasheet - Page 8

• Manufacturer Part Number: MAX6650EUB+T
• Description: IC REG FAN SPEED 10-MSOP
• Manufacturer: Maxim Integrated Products

Specifications of MAX6650EUB+T

• Applications: Fan Controller, Brushless (BLDC)
• Number Of Outputs: 1
• Voltage - Load: 0.3 V ~ 5.2 V
• Voltage - Supply: 3 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 10-MSOP, Micro10™, 10-uMAX, 10-uSOP
• Operating Supply Voltage: 3 V to 5.5 V
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Output: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: MAX6650EUB+T; MAX6650EUB+TTR

Fan-Speed Regulators and Monitors
with SMBus/I
Figure 3. SMBus Write Timing Diagram
Figure 4. SMBus Read Timing Diagram
The 8-bit Command-Byte Register (Table 2) is the mas-
ter index that points to the various other registers within
MAX6650/MAX6651. The register’s power-on reset
(POR) state is 0000 0000, so that a receive-byte trans-
mission (a protocol that lacks the command byte)
occurring immediately after POR returns the current
speed setting.
In closed-loop mode, the MAX6650/MAX6651 use the
Fan-Speed Register to set the period of the tachometer
signal that controls the fan speed. The Fan-Speed
Register is ignored in all other modes of operation. The
MAX6650/MAX6651 regulate the fan speed by forcing
the tachometer period (t
ister value. One revolution of the fan generates two
8
SMBCLK
SMBDATA
_______________________________________________________________________________________
SMBCLK
SMBDATA
A = START CONDITION
B = MSB OF ADDRESS CLOCKED INTO SLAVE
C = LSB OF ADDRESS CLOCKED INTO SLAVE
D = R/W BIT CLOCKED INTO SLAVE
E = SLAVE PULLS SMBDATA LINE LOW
A = START CONDITION
B = MSB OF ADDRESS CLOCKED INTO SLAVE
C = LSB OF ADDRESS CLOCKED INTO SLAVE
D = R/W BIT CLOCKED INTO SLAVE
t
SU:STA
t
SU:STA
A
t
HD:STA
A
t
HD:STA
t
LOW
Command-Byte Functions
t
LOW
TACH
B
t
HIGH
B
t
HIGH
) equal to the scaled reg-
Fan-Speed Register
2
C-Compatible Interface
t
SU:DAT
t
SU:DAT
C
C
F = ACKNOWLEDGE BIT CLOCKED INTO MASTER
G = MSB OF DATA CLOCKED INTO SLAVE
H = LSB OF DATA CLOCKED INTO SLAVE
I = SLAVE PULLS SMBDATA LINE LOW
E = SLAVE PULLS SMBDATA LINE LOW
F = ACKNOWLEDGE BIT CLOCKED INTO MASTER
G = MSB OF DATA CLOCKED INTO MASTER
H = LSB OF DATA CLOCKED INTO MASTER
D
D
E
E
F
F
tachometer pulses, so the required Fan-Speed Register
value (K
where the fan speed is in rotations per second (RPS),
t
internal oscillator frequency (254kHz ±10%), and
K
Register ). Since the fan speed is inversely proportional
to the tachometer period, the Fan-Speed Register value
(K
3). Select the prescaler value so the fan’s full speed is
achieved with a register value of approximately 64
(0100 0000) to optimize speed range and resolution.
The MAX6651 may be controlled by an external oscilla-
TACH
SCALE
TACH
t
HD:DAT
t
K
TACH
is the period of the tachometer signal, f
TACH
) does not linearly control the fan speed (Table
G
G
TACH )
is the prescaler value (see Configuration-Byte
= 1 / (2 x Fan Speed)
= [t
may be calculated as:
TACH
H
J = ACKNOWLEDGE CLOCKED INTO MASTER
K = ACKNOWLEDGE CLOCK PULSE
L = STOP CONDITION, DATA EXECUTED BY SLAVE
M = NEW START CONDITION
I = ACKNOWLEDGE CLOCK PULSE
J = STOP CONDITION
K = NEW START CONDITION
x K
H
SCALE
I
J
x (f
I
CLK
t
SU:STO
K
/ 128)] - 1
t
SU:STO
J
t
BUF
L
t
CLK
BUF
K
M
is the