NXP Semiconductors LPC2917, LPC2919 user manual Draft, Analog-to-digital converter

NXP Semiconductors

DRAFT	D	D		AFT
	RAFT	RAFT AFT
			DR	DR

DLPC2917/19

ARM9 microcontrollerRAFT withDRAFTCANDRAFTand LINDRAFT

		T DRAFT			T
		DRA		DRA		DR
		F	DRAFT		F
•		DRAFT				DRAF
	CLK_SYS_MSCSS_A clocks the AHB side of the AHB-to-VPB bus bridge
•	CLK_MSCSS_VPB clocks the subsystem VPB bus	DRAFT			DRAFT
•	CLK_MSCSS_MTMR0/1 clocks the timers
•	CLK_MSCSS_PWM0..3 clocks the PWMs.					D
				DRAFT
Each ADC has two clock areas; a VPB part clocked by CLK_MSCSS_ADCx_VPB (x = 1						DRA
or 2) and a control part for the analog section clocked by CLK_ADCx = 1 or 2), see

Section 7.2.2.

All clocks are derived from the BASE_MSCSS_CLK, except for CLK_SYS_MSCSS_A which is derived form BASE_SYS_CLK, and the CLK_ADCx clocks which are derived from BASE_CLK_ADC. If specific PWM or ADC modules are not used their corresponding clocks can be switched off.

8.7.5Analog-to-digital converter

8.7.5.1Overview

The MSCSS in the LPC2917/19 includes two 10-bit successive-approximation analog-to-digital converters.

The key features of the ADC interface module are:

•ADC1 and ADC2: Eight analog inputs; time-multiplexed; measurement range up to 3.3 V

•External reference-level inputs

•400 ksamples per second at 10-bit resolution up to 1500 ksamples per second at 2-bit resolution

•Programmable resolution from 2-bit to 10-bit

•Single analog-to-digital conversion scan mode and continuous analog-to-digital conversion scan mode

•Optional conversion on transition on external start input, timer capture/match signal, PWM_sync or ‘previous’ ADC

•Converted digital values are stored in a register for each channel

•Optional compare condition to generate a ‘less than’ or an ‘equal to or greater than’ compare-value indication for each channel

•Power-down mode

8.7.5.2Description

The ADC block diagram, Figure 9, shows the basic architecture of each ADC. The ADC functionality is divided into two major parts; one part running on the MSCSS Subsystem clock, the other on the ADC clock. This split into two clock domains affects the behavior from a system-level perspective. The actual analog-to-digital conversions take place in the ADC clock domain, but system control takes place in the system clock domain.

A mechanism is provided to modify configuration of the ADC and control the moment at which the updated configuration is transferred to the ADC domain.

LPC2917_19_1 © NXP B.V. 2007. All rights reserved.

Preliminary data sheet Rev. 1.01 — 15 November 2007 35 of 68