LM3S8G62 Datasheet, PDF (51/1096 Pages) Texas Instruments – Stellaris® LM3S8G62 Microcontroller

OBSOLETE: TI has discontinued production of this device.
Stellaris^® LM3S8G62 Microcontroller
1.3.5.1
■ Two Quadrature Encoder Inputs (QEI)
The following provides more detail on these motion control functions.
PWM (see page 878)
Pulse width modulation (PWM) is a powerful technique for digitally encoding analog signal levels.
High-resolution counters are used to generate a square wave, and the duty cycle of the square
wave is modulated to encode an analog signal. Typical applications include switching power supplies
and motor control. The LM3S8G62 PWM module consists of three PWM generator blocks and a
control block. Each PWM generator block contains one timer (16-bit down or up/down counter), two
comparators, a PWM signal generator, a dead-band generator, and an interrupt/ADC-trigger selector.
Each PWM generator block produces two PWM signals that can either be independent signals or
a single pair of complementary signals with dead-band delays inserted.
Each PWM generator has the following features:
■ Four fault-condition handling inputs to quickly provide low-latency shutdown and prevent damage
to the motor being controlled
■ One 16-bit counter
– Runs in Down or Up/Down mode
– Output frequency controlled by a 16-bit load value
– Load value updates can be synchronized
– Produces output signals at zero and load value
■ Two PWM comparators
– Comparator value updates can be synchronized
– Produces output signals on match
■ PWM signal generator
– Output PWM signal is constructed based on actions taken as a result of the counter and
PWM comparator output signals
– Produces two independent PWM signals
■ Dead-band generator
– Produces two PWM signals with programmable dead-band delays suitable for driving a half-H
bridge
– Can be bypassed, leaving input PWM signals unmodified
■ Can initiate an ADC sample sequence
The control block determines the polarity of the PWM signals and which signals are passed through
to the pins. The output of the PWM generation blocks are managed by the output control block
before being passed to the device pins. The PWM control block has the following options:
■ PWM output enable of each PWM signal
July 24, 2012
51
Texas Instruments-Production Data