1FEATURES
23456· Remote Temperature Sensor:
±2°C Accuracy, 0.125°C Resolution
· Local Temperature Sensor:
±2°C Accuracy, 0.125°C Resolution
· PWM Controller
· PWM Frequency: 10Hz to 40kHz
Duty Cycle: 0% to 100%, 8 Bits
· Automatic Fan Speed Control Loops
· SMBus Interface
· Power: 2.7V to 5.5V
· Package (Green): QSOP-16 (4mm ´ 5mm)
· RoHS Compliant

APPLICATIONS
· Notebook and Desktop PCs
· Network Servers
· Telecommunications Equipment
· PC-Based Equipment
· DLP™ and LCD Projectors

DESCRIPTION
The AMC6821 is an intelligent temperature monitor
and pulse-width modulation (PWM) fan controller. It is
designed for noise-sensitive or power-sensitive
applications that require active system cooling. Using
either a low-frequency or a high-frequency PWM signal, this device can simultaneously drive a fan,
monitor remote sensor diode temperatures, and
measure and control the fan speed so that it operates
with minimal acoustic noise at the lowest possible
speed.
The AMC6821 has three fan control modes: Auto
Temperature-Fan mode, Software-RPM mode, and
Software-DCY mode. Each mode controls the fan
speed by changing the duty cycle of a PWM output.
Auto Temperature-Fan mode is an intelligent,
closed-loop control that optimizes fan speed
according to user-defined parameters. This mode
allows the AMC6821 to run as a stand-alone device without CPU intervention; the fan can continue to be
controlled (based on temperature measurements)
even if the CPU or system locks up. Software-RPM
mode is a second closed-loop control. In this mode,
the AMC6821 adjusts the PWM output to maintain a
consistent fan speed at a user-specified target value;
that is, the device functions as a fan speed regulator.
Software-RPM mode can also be used to allow the
AMC6821 to operate as a stand-alone device. The
third mode, Software-DCY, is open-loop. In
Software-DCY mode, the PWM duty cycle is set
directly by the value written to the device.
The AMC6821 has a programmable SMBALERT
output to indicate error conditions and a dedicated
FAN-FAULT output to indicate fan failure. The
THERM pin is a fail-safe output for over-temperature
conditions that can be used to throttle a CPU clock.
Additionally, the OVR pin indicates the
over-temperature limit as well. All of the alarm
thresholds are set through the device registers. The
AMC6821 is available in a QSOP-16 package.