LPC1837FET256,551 NXP Semiconductors, LPC1837FET256,551 Datasheet - Page 636

• Manufacturer Part Number: LPC1837FET256,551
• Description: Microcontrollers (MCU) 32BIT ARM CORTEX-M3 MCU 136KB SRAM
• Manufacturer: NXP Semiconductors
• Series: LPC18xxr

Specifications of LPC1837FET256,551

• Core: ARM Cortex M3
• Core Processor: ARM® Cortex-M3™
• Core Size: 32-Bit
• Speed: 150MHz
• Connectivity: CAN, EBI/EMI, Ethernet, I²C, Microwire, SD/MMC, SPI, SSI, SSP, UART/USART, USB OTG
• Peripherals: Brown-out Detect/Reset, DMA, I²S, Motor Control PWM, POR, PWM, WDT
• Number Of I /o: 80
• Program Memory Size: 1MB (1M x 8)
• Program Memory Type: FLASH
• Eeprom Size: -
• Ram Size: 136K x 8
• Voltage - Supply (vcc/vdd): 2 V ~ 3.6 V
• Data Converters: A/D 16x10b; D/A 1x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 256-LBGA
• Lead Free Status / Rohs Status: Details
• Other names: 935293795551

NXP Semiconductors
<Document ID>
User manual
The MCPWM includes 3 channels, each of which controls a pair of outputs that in turn can
control something off-chip, like one set of coils in a motor. Each channel includes a
Timer/Counter (TC) register that is incremented by a processor clock (timer mode) or by
an input pin (counter mode).
Each channel has a Limit register that is compared to the TC value, and when a match
occurs the TC is “recycled” in one of two ways. In “edge-aligned mode” the TC is reset to
0, while in “centered mode” a match switches the TC into a state in which it decrements on
each processor clock or input pin transition until it reaches 0, at which time it starts
counting up again.
Each channel also includes a Match register that holds a smaller value than the Limit
register. In edge-aligned mode the channel’s outputs are switched whenever the TC
matches either the Match or Limit register, while in center-aligned mode they are switched
only when it matches the Match register.
So the Limit register controls the period of the outputs, while the Match register controls
how much of each period the outputs spend in each state. Having a small value in the
Limit register minimizes “ripple” if the output is integrated into a voltage, and allows the
MCPWM to control devices that operate at high speed.
The “downside” of small values in the Limit register is that they reduce the resolution of
the duty cycle controlled by the Match register. If you have 8 in the Limit register, the
Match register can only select the duty cycle among 0%, 12.5%, 25%, …, 87.5%, or
100%. In general, the resolution of each step in the Match value is 1 divided by the Limit
value.
This trade-off between resolution and period/frequency is inherent in the design of pulse
width modulators.
All information provided in this document is subject to legal disclaimers.
Rev. 00.13 — 20 July 2011
Chapter 26: LPC18xx Motor Control PWM (MOTOCONPWM)
UM10430
© NXP B.V. 2011. All rights reserved.
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