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.