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ZXBM1021JB20TC Datasheet(PDF) 7 Page - Diodes Incorporated |
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ZXBM1021JB20TC Datasheet(HTML) 7 Page - Diodes Incorporated |
7 / 24 page ZXBM1021 Document number: DS Draft Rev. 1 7 of 24 www.diodes.com June 2013 © Diodes Incorporated ZXBM1021 Functional Descriptions H-Bias – Hall Bias Output This is a 1.75V nominal voltage source to bias a differential un-buffered Hall element sensor. If a Hall element requires a lower voltage than the H-Bias output, connect an appropriate value resistor between the H-Bias pin and the Hall element supply pin. H+ and H- – Hall Inputs The rotor position is detected by a Hall sensor, with the output applied to the H+ and H-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 H+ and H- pins. For a buffered Hall sensor the Hall device output is attached to the H+ pin, with a pull-up attached if needed, whilst the H- pin has an external potential divider attached to hold the pin at half VThRef. When H+ is high in relation to H-, Ph2 is the active drive. ThRef – Output Reference Voltage This is a 5V nominal reference output voltage. It is designed to 'source' current and therefore it will not 'sink' any current from a higher voltage. The total current drawn from the ThRef pin by any external circuitry, such as the minimum speed potential divider to SMIN pin, should not exceed 10mA. SPD –Speed control DC Voltage Input The voltage applied to the SPD pin provides control over the fan motor speed by varying the Pulse Width Modulated (PWM) drive ratio at the Ph1Lo and Ph2Lo outputs. The control signal takes the form of a variable DC voltage input of range 3V to 1V, representing 0% to 100% drive respectively. If variable speed control is not required this pin can be tied to an external potential divider to set a fixed speed or tied to ground to provide full speed i.e. 100% PWM drive. If required this pin can also be used as an enable pin. The application of a voltage >3.0V on this pin will force the PWM drive fully off, in effect disabling the drive, providing the minimum speed function is not active (see SMIN pin section below). To use a minimum speed setting or current control in DC voltage speed control mode, add a series resistor 10k or greater (R11 in typical application circuit for DC control in page 2) between speed control DC voltage input source and SPD pin. PWMSPD – Speed Control PWM Signal Input The duty ratio of the speed control PWM signal input to this pin controls the fan motor speed by varying the output drive PWM ratio at the Ph1Lo and Ph2Lo outputs. In the PWM speed control mode, the PWMSPD pin and the CSPD pin work together to the control the speed. The PWM signal input on the PWMSPD pin is integrated by the capacitor on the CSPD pin (See CSPD pin description). PWM control input signal to the PWMSPD pin needs to be a TTL logic levels. CSPD – PWM Speed Control Signal Integrator Output When PWM input signal is used to control the motor speed, PWM signal is integrated to DC voltage between 1V to 3V to for speed control. If PWMSPD pin input is TTL low, the output voltage on CSPD is 3V and if PWMSPD pin is TTL high, the CSPD pin output is at 1V. In order for the integrator function to be fulfilled an external capacitor is required. This would normally be a 0.1 F capacitor for a 25kHz input PWM frequency applied to the PWMSPD input. In PWM speed control mode, connect 0.1 F capacitor from CSPD pin to ground and connect CSPD pin to SPD pin. When in DC voltage speed control mode keep PWMSPD and CSPD pins unconnected. SMIN – Minimum Speed Setting A voltage can be set on this pin via a potential divider between the ThRef and GND pins. This voltage is monitored by the SPD pin to clamp the SPD control voltage so that it does not rise above SMIN voltage. As a higher voltage on the SPD pin represents a lower speed, the SMIN setting prevents the motor speed going lower than the minimum speed set by the SMIN pin. If this feature is not required the pin is left tied to ThRef so no minimum speed will be set. If the fan is being controlled from an external voltage source onto the SPD pin then either this feature should not be used or if the minimum speed setting is required then a 10k or greater resistor should be placed in series with the SPD pin. |
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