MAX31790_15 Datasheet, PDF (1/43 Pages) Maxim Integrated Products – 6-Channel PWM-Output Fan RPM Controller

MAX31790
EVALUATION KIT AVAILABLE
6-Channel PWM-Output Fan RPM Controller
General Description
The MAX31790 controls the speeds of up to six fans
using six independent PWM outputs. The desired fan
speeds (or PWM duty cycles) are written through the I²C
interface. The outputs drive “4-wire” fans directly, or can
be used to modulate the fan’s power terminals using an
external pass transistor.
Tachometer inputs monitor fan tachometer logic outputs
for precise (Q1%) monitoring and control of fan RPM as
well as detection of fan failure. Six pins are dedicated
tachometer inputs. Any of the six PWM outputs can also
be configured to serve as tachometer inputs.
The PWM_START inputs select the PWM output status
at startup to ensure appropriate fan drive when power is
first applied.
To ensure low acoustic impact of fan control, all changes
in PWM duty cycle take place at a controlled, program-
mable rate.
The MAX31790’s 3.0V to 5.5V supply voltage range and
I²C-compatible interface make it ideal for fan control in
a wide range of cooling applications. The MAX31790 is
available in a 28-pin TQFN package and operates over
the -40NC to +125NC temperature range.
Benefits and Features
●● Provides Precise Fan Control and Monitoring for
Large Fan Count Applications
• Controls Up to Six Independent Fans with PWM
Drive
• Up to 12 Tachometer Inputs
• Controlled Duty Cycle Rate-of-Change for Best
Acoustics
●● Improves System Reliability
• Versatile Startup Configurations Provide Reliable
Fan Control at Power-up without Having to Wait for
System µC Direction
• I²C Bus Interface with Timeout and Watchdog
Applications
●● Servers
●● Networking
●● Telecom
Ordering Information appears at end of data sheet.
For related parts and recommended products to use with this part,
refer to: www.maximintegrated.com/MAX31790.related
Typical Operating Circuit
HOST
INTERFACE
SET
POWER-UP
VALUES
CRYSTAL
(OPTIONAL)
VCC
3.0V TO 5.5V
VCC
12pF
RPU
SDA
SCL
FAN_FAIL
FULL_SPEED
XTAL1 XTAL2
12pF
VCC
MAX31790
0.1µF
VCC
PWMOUT1
TACH1
PWMOUT2
V4-WIRE FAN
FAN1
CLKOUT
PWM_START1
PWM_START0
FREQ_START
SPIN_START
WD_START
ADD1
ADD0
I²C INTERFACE,
REGISTERS,
AND
CONTROL LOGIC
TACH2
PWMOUT3
PWM OUTPUT
DRIVER,
TACH MONITOR
TACH3
PWMOUT4
TACH4
PWMOUT5
TACH5
PWMOUT6
TACH6
GND
6 CHANNELS
19-6540; Rev 2; 1/15