Datasheet

19-4039; Rev 1; 1/13
MAX6620
Quad Linear Fan-Speed Controller
EVALUATION KIT AVAILABLE
For pricing, delivery, and ordering information, please contact Maxim Direct
at 1-888-629-4642, or visit Maxim’s website at www.maximintegrated.com.
General Description
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
2
C interface. Each output drives the base of an
external bipolar transistor or the gate of a FET in high-
side drive configuration. Voltage feedback at the fan’s
power-supply terminal is used to force the correct out-
put voltage.
The MAX6620 offers two methods for fan control. In
RPM mode, the MAX6620 monitors four fan tachometer
logic outputs for precise (±1%) control of fan RPM and
detection of fan failure. In DAC mode, each fan is dri-
ven with a voltage resolution of 9 bits and the tachome-
ter outputs of the fans are monitored for failure.
The DAC_START input selects the fan power-supply
voltage at startup to ensure appropriate fan drive when
power is first applied. A watchdog feature turns the
fans fully on to protect the system if there are no valid
I
2
C communications within a preset timeout period.
The MAX6620 operates from a 3.0V to 5.5V power sup-
ply with low 250µA supply current, and the I
2
C-compati-
ble interface makes it ideal for fan control in a wide
range of cooling applications. The MAX6620 is avail-
able in a 28-pin TQFN package and operates over the
-40°C to +125°C automotive temperature range.
Applications
Consumer Products
Servers
Communications Equipment
Storage Equipment
Features
o Controls Up to Four Independent Fans With
Linear (DC) Drive
o Uses Four External Low-Cost Pass Transistors
o 1% Accuracy Precision RPM Control
o Controlled Voltage Rate-Of-Change for Best
Acoustics
o I
2
C Bus Interface
o 3.0V to 5.5V Supply Voltage Range
o 250µA (typ) Operating Supply Current
o 3µA (typ) Shutdown Supply Current
o Small 5mm x 5mm Footprint
MAX6620
TQFN
(5mm
×
×
5mm × 0.8mm)
TOP VIEW
26
27
25
24
10
9
11
SDA
GND
ADDR
DAC_START
SPINUP_START
12
SCL
+
DACFB2
GND
DACOUT3
TACH2
DACFB3
TACH3
12
GND
4567
2021 19 17 16 15
FAN
VCC
DACOUT4
GND
GND
X2
WD_START
DACOUT2
3
18
28
8
FAN_FAIL
X1
DACOUT1
23
13
DACFB4
DACFB1
22
14
TACH4
TACH1
Pin Configuration
Ordering Information
+
Denotes a lead-free package.
*
EP = Exposed paddle.
PART TEMP RANGE PIN-PACKAGE
MAX6620ATI+
-40°C to +125°C 28 TQFN-EP*
Typical Application Circuit appears at end of data sheet.

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