LMD18201

SNVS092D – APRIL 1998 – REVISED APRIL 2013

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APPLICATION INFORMATION

TYPES OF PWM SIGNALS

The LMD18201 readily interfaces with different forms of PWM signals. Use of the part with two of the more

popular forms of PWM is described in the following paragraphs.

Simple, locked anti-phase PWM consists of a single, variable duty-cycle signal in which is encoded both

direction and amplitude information (see Figure 9). A 50% duty-cycle PWM signal represents zero drive, since

the net value of voltage (integrated over one period) delivered to the load is zero. For the LMD18201, the PWM

signal drives the direction input (pin 3) and the PWM input (pin 5) is tied to logic high.

Figure 9. Locked Anti-Phase PWM Control

Sign/magnitude PWM consists of separate direction (sign) and amplitude (magnitude) signals (see Figure 10).

The (absolute) magnitude signal is duty-cycle modulated, and the absence of a pulse signal (a continuous logic

low level) represents zero drive. Current delivered to the load is proportional to pulse width. For the LMD18201,

the DIRECTION input (pin 3) is driven by the sign signal and the PWM input (pin 5) is driven by the magnitude

signal.

Figure 10. Sign/Magnitude PWM Control

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