AM9468

Document number: DS38663 Rev. 1 - 2

9 of 16

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May 2016

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AM9468

Application Note

HIN-Bias

– Hall Bias Output

This is a 1.25V nominal voltage source to bias a differential un-buffered Hall element sensor. If a Hall element requires a lower voltage than the

HIN-Bias output, connect an appropriate value resistor between the HIN-Bias pin and the Hall element supply pin.

HIN+ and HIN-

– Hall Inputs

The rotor position is detected by a Hall sensor, with the output of Hall sensor applied to the HIN+ and HIN- pins. This sensor can be either a 4

pin 'naked' Hall device or of the 3 pin buffered switching type. For a 4 pin device the differential Hall output signal is connected to the HIN+ and

HIN- pins. For a buffered Hall sensor the Hall device output is attached to the HIN+ pin, with a pull-up attached if needed, whilst the HIN- pin has

PWM Pin - External PWM Signal Input for PWM Speed Control Mode

In PWM speed control mode, external PWM signal is applied at this PWM pin to control the motors speed. The duty ratio of the PWM signal input

to this pin controls the fan motor speed by varying the output PWM drive directly.

CPWM Pin

triangular wave of 36kHz (typ). The VCONT and RMI signals are compared with this triangular wave to generate the speed control PWM drive

and minimum speed control clamp points. The output PWM drive frequency is same as the triangular waveform frequency.

FG/RD Pin

FG is the Frequency Generator (tachometer) output and is a buffered signal from the Hall sensor. RD is the fan locked status detector. FG and

RD are open-drain outputs and will require external pull-up resistors. Typically a pull-up resistor of 10k

Ω is recommended from FG and RD pins

to the supply voltage.

RF Pin

The current limiter is activated when the voltage between current detection resistor exceeds 0.25V between GND and RF. The current limiter is

RMI Pin

– Minimum Speed Setting Pin

RMI is the minimum speed setting pin. DC voltage on this pin sets minimum speed value; If you do not use RMI (minimum speed control), please

connect it to 5VREG.

VCONT Pin

– DC Voltage Speed Control

VCONT is DC voltage inputs speed control pin. The voltage on the VCONT pin is compared with the triangular oscillation on the CPWM pin to

generate the output drive PWM signal. For the control method, refer to the timing chart.

.

REGH/5VREG Pin

Please insert capacitor value 1µF between 5VREG and GND for regulated output voltage stabilization; insert capacitor value 1µF value between

OUT1 and OUT2 pin

OUT1 and OUT2 pins provide H-bridge driver output for fan and motor coil connection.

This provides the supply for the device.

GND

– Supply Return

This is the device supply ground return pin for control signal.