MAX6620ATI+ Maxim Integrated Products, MAX6620ATI+ Datasheet - Page 8

• Manufacturer Part Number: MAX6620ATI+
• Description: IC QUAD LIN FAN-SPD CTRLR 28TQFN
• Manufacturer: Maxim Integrated Products

Specifications of MAX6620ATI+

• Applications: Fan Controller
• Number Of Outputs: 4
• Voltage - Supply: 3 V ~ 5.5 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 28-TQFN Exposed Pad
• Mounting Style: SMD/SMT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Output: -
• Voltage - Load: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

Quad Linear Fan-Speed Controller
The MAX6620 controls the speeds of up to four fans
using four independent linear voltage outputs. The
drive voltages for the fans are controlled directly over
the I
DACOUT4) drive the base of an external PNP or the
gate of a p-channel MOSFET. Voltage feedback at the
fan’s power-supply terminal is used to force the output
voltage.
The MAX6620 monitors fan tachometer logic outputs for
precise (1%) control of fan RPM and detection of fan
failure. When the MAX6620 is used with 2-wire fans,
these inputs are not used, and the fans can be driven
to the desired voltage without using tachometer feed-
back.
Three inputs set the fan drive status on application of
power. The DAC_START input selects the fan-supply
voltage (100%, 75%, or 0%) at startup to ensure appro-
priate fan drive when power is first applied. The
SPIN_START input selects whether spin-up will be
applied to the fans at power-up. WD_START selects
Figure 2. I
8
Write Byte Format
Read Byte Format
Send Byte Format
S = START CONDITION
P = STOP CONDITION
S
S
_______________________________________________________________________________________
2
S
C interface. Each of the outputs (DACOUT1–
ADDRESS
Slave Address: equiva-
lent to chip-select line
ADDRESS
2
7 bits
C Protocols
Slave Address: equiva-
lent to chip-select line of
a 3-wire interface
7 bits
ADDRESS
7 bits
WR
WR
Detailed Description
A
WR
A
Command Byte: sends com-
mand with no data, usually
used for one-shot command
SHADED = SLAVE TRANSMISSION
A = NOT ACKNOWLEDGED
COMMAND
8 bits
Command Byte: selects
which register you are
reading from
COMMAND
8 bits
A
Command Byte: selects which
register you are writing to
A
COMMAND
A
P
8 bits
S
Receive Byte Format
whether lack of I
speed. When the watchdog function is enabled, the
fans will be driven to full speed if there is no I
for a period of 2s, 6s, or 10s.
The MAX6620 features an I
interface consisting of a bidirectional serial data line
(SDA) and a serial clock line (SCL). SDA and SCL facili-
tate bidirectional communication between the MAX6620
and the master at rates up to 400kHz. The master (typi-
cally a microcontroller) initiates data transfer on the bus
and generates SCL. SDA and SCL require 4.7kΩ (typ)
pullup resistors.
One data bit is transferred during each SCL clock
cycle. Nine clock cycles are required to transfer the
data into or out of the MAX6620. The data on SDA must
remain stable during the high period of the SCL clock
pulse, as changes in SDA while SCL is high are control
signals (see the START and STOP Conditions section).
Both SDA and SCL idle high.
S
Slave Address: repeated
due to change in data-
flow direction
ADDRESS
7 bits
ADDRESS
7 bits
A
Data Byte: data goes into the register
set by the command byte (to set
thresholds, configuration masks, and
sampling rate)
RD
2
C activity will force the fans to full
DATA
RD
8 bits
A
2
A
C-compatible, 2-wire serial
Data Byte: reads data from
the register commanded
by the last read byte or
write byte transmission;
also used for SMBus alert
response return address
Data Byte: reads from
the register set by the
command byte
DATA
8 bits
DATA
8 bits
Digital Interface
A
Bit Transfer
A
A
2
C activity
P
1
P
P