AMC8500 Datasheet, PDF (17/27 Pages) List of Unclassifed Manufacturers – TWO PHASE VARIABLE SPEED FAN MOTOR CONTROLLER

Preliminary Specification
aMC8500
Figure 33- Pin Function Description
Pin
Function
Description
1 Phase 2 Output
This output directly drives phase 2 of a unipolar motor. It is active low when the voltage applied to the Hall -
input exceeds that of Hall +.
This input is left unconnected for a maximum motor drive current sink current of 1100 mA. The sink current
2 Current Limit Set can be programmed to a lower level by connecting a resistor from this input to ground. Most applications will
require a 10 nF bypass capacitor on this pin to prevent noise pick up.
3 Hall +
This input connects to the output of an unbuffered differential type Hall sensor.
4 Hall -
This input connects to the output of an unbuffered differential type Hall sensor.
This is the reference output and is capable of sourcing in excess of 10 mA. It is also used to selectively
5 Reference Output enable or disable the automatic power down feature. Automatic power down is enabled if the reference load
current is 1.0 mA or less, and disabled if it is 2.0 mA or more.
This input is used in conjunction with the Reference Output to program the minimum motor speed or the
6
Minimum Speed
Set
threshold for automatic power down. If continuous minimum speed operation is desired, the automatic power
down feature must be disabled. The minimum speed set feature is not available when controlling motor
speed from a variable duty cycle digital pulse train and this input must be disabled by connected it to Pin 14.
7
Non-Inverting Input
This is the non-inverting input of the Op Amp. It has an operating voltage range that extends from ground to
4.2 V.
8 Inverting Input
This is the inverting input of the Op Amp. It has an operating voltage range that extends from ground to
4.2 V.
9 Op Amp Output
This is the Op Amp output and it is capable of sinking or sourcing up to of 10 mA. The Op Amp can be used
in conjunction with the Reference for scaling a speed control signal derived from a temperature sensor.
10
Speed Control
Input
A voltage level that ranges from 1.0 V to 3.0 V or a variable duty cycle pulse is applied to this input for
controlling the motor speed. A positive or negative speed control slope can be selected via Pin 14.
11 Signal Gnd
This pin is the ground return for the control circuitry. It connects directly to the power source ground terminal.
Internally this pin connects to the device substrate and the exposed thermal pad.
12 V_DD
This pin is the control circuit positive supply. It connects to the power source positive terminal.
13 Power Ground
This pin is the ground return for the motor drive MOSFETs. It connects to the power source ground terminal.
This input selects between a positive or a negative speed control slope. When connected to ground, an
14 Slope Select
increasing voltage at Pin 6 or 10 increases motor speed. When not connected, an increasing voltage at Pin 6
or 10 decreases motor speed. This input has an internal 10 μA current source pull-up.
This output provides a digital square wave signal that switches at the Hall sensor frequency and is active low
15
Freq. Generator /
Rotor Lock
when the voltage applied to the Hall - input exceeds that of the Hall +. If the motor turns too slow or is
stalled, the output will assume a high state. This is an active low open drain output and it requires a pull-up
resistor.
16 Phase 1 Output
This output directly drives phase 1 of a unipolar motor. It is active low when the voltage applied to the Hall +
input exceeds that of Hall -.
Layout Considerations
High frequency printed circuit layout techniques are required to prevent pulse jitter and the possibility of erratic operation.
This can be caused by excessive noise pick-up imposed upon the Hall or Error Amplifier inputs. The printed circuit layout
should contain as much copper ground as possible with separate low current signal and high current motor drive grounds
that return back to the power supply input filter capacitor. Ceramic 0.1 µF bypass capacitors connected close to the
integrated circuit V_DD and V_ref pins may also be required depending upon circuit board layout and the source voltage
impedance. The use of bypass capacitors will provide a low impedance path to ground for filtering out high frequency noise.
The signal and power ground pins along with the exposed thermal pad must be connected together at the package. All high
current loops should be kept as short as possible with wide traces to minimize the generation of radiated electro magnetic
interference, EMI. Wide copper trace connections with copious amounts of foil placed under the device will greatly enhance
the devices ability to dissipate power.
© Andigilog, Inc. 2006
- 17 -
www.andigilog.com
August 2006 - 70A04018