LM3S2965-IQC20-A0T Luminary Micro, Inc., LM3S2965-IQC20-A0T Datasheet - Page 458

• Manufacturer Part Number: LM3S2965-IQC20-A0T
• Description: Microcontroller
• Manufacturer: Luminary Micro, Inc.

Pulse Width Modulator (PWM)
18
18.1
18.2
18.2.1
458
Pulse Width Modulator (PWM)
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 Stellaris
PWM generator block contains one timer (16-bit down or up/down counter), two PWM comparators,
a PWM signal generator, a dead-band generator, and an interrupt/ADC-trigger selector. The control
block determines the polarity of the PWM signals, and which signals are passed through to the pins.
Each PWM generator block produces two PWM signals that can either be independent signals
(other than being based on the same timer and therefore having the same frequency) or a single
pair of complementary signals with dead-band delays inserted. The output of the PWM generation
blocks are managed by the output control block before being passed to the device pins.
The Stellaris
such as those required by a simple charge pump. It can also generate paired PWM signals with
dead-band delays, such as those required by a half-H bridge driver. It can also generate the full six
channels of gate controls required by a 3-Phase inverter bridge.
Block Diagram
Figure 18-1 on page 458 provides a block diagram of a Stellaris
controller contains three generator blocks (PWM0, PWM1, and PWM2) and generates six independent
PWM signals or three paired PWM signals with dead-band delays inserted.
Figure 18-1. PWM Module Block Diagram
Functional Description
PWM Timer
The timer in each PWM generator runs in one of two modes: Count-Down mode or Count-Up/Down
mode. In Count-Down mode, the timer counts from the load value to zero, goes back to the load
value, and continues counting down. In Count-Up/Down mode, the timer counts from zero up to the
PWM Clock
®
®
PWM module provides a great deal of flexibility. It can generate simple PWM signals,
PWM module consists of three PWM generator blocks and a control block. Each
PWMnCOUNT
PWMnLOAD
16
Timer
Comparator A
Comparator B
PWMnCMPA
PWMnCMPB
zero
load
dir
cmpA
cmpB
Preliminary
Trigger Generate
Interrupt and
PWMnINTEN
PWMnGENA
PWMnGENB
Generator
PWMnRIS
PWMnISC
PWM
pwma
pwmb
PWM Generator Block
®
PWM module. The LM3S2965
PWMnDBRISE
PWMnDBCTL
PWMnDBFALL
Dead-Band
Generator
Fault
Interrupt
PWM Output
PWMENABLE
PWMINVERT
PWMFAULT
Control
June 04, 2007