Freescale公司的MC9RS08KA2系列微控制器是超低成本低引腳數(shù)器件，特別適合家用電器，玩具和小型設(shè)備的應(yīng)用。創(chuàng)新的高亮LED解決方案在低成本應(yīng)用中迅速增長，但是低端高亮LED解決方案需要高級的系統(tǒng)控制和大恒流電流來維持色彩完整性和高的亮度輸出。本文介紹采用MC9RS08KA2的主要性能，以及用MC9RS08KA2控制的高亮LED解決方案的電路圖。

Innovative HBLED solutions are rapidly gaining popularity in low-cost applications
that require an extremely cost-effective bill-of-materials. However, low-end HBLED
applications still require a high level of system control as well as high constant-current to
maintain color integrity and high light output.
Freescale’s general-purpose ultra-low-end KA2 8-bit MCU offers an economical solution for this application. The on-chip analog comparator is designed to provide an accurate current measurement, which allows feedback control to maintain a constant level in the LED forward current.


MC9RS08KA2 Controlled High-Brightness LED



The MC9RS08KA2 Series microcontroller unit (MCU) is an extremely low-cost, small pin count device for home appliances, toys, and small geometry applications. This device is composed of standard on-chip modules including, a very small and highly efficient RS08 CPU core, 63 bytes RAM, 2K bytes Flash, an 8-bit modulo timer, keyboard interrupt, and analog comparator. The device is available in small 6- and 8-pin packages.



圖1。MC9RS08KA2系列方框圖

MC9RS08KA2主要特性：
8-Bit RS08 Central Processor Unit (CPU)
Simplified S08 instruction set with added high-performance instructions
LDA, STA, and CLR instructions support the short addressing mode; address $0000 to $001F can be accessed via a single-byte instruction
ADD, SUB, INC, and DEC instructions support the tiny addressing mode;
address $0000 to $000F can be accessed via a single-byte instruction with reduced instruction cycle
Shadow PC register instructions: SHA and SLA
Pending interrupt indication
Index addressing via D[X] and X register
Direct page access to the entire memory map through paging window
Memory
On-chip Flash EEPROM
MC9RS08KA2: 2048 bytes
MC9RS08KA1: 1024 bytes
63 bytes on-chip RAM
Power-Saving Modes
Wait and stop
Wakeup from power-saving modes using real-time interrupt (RTI), KBI, or ACMP
Clock Source
ICS — Trimmable 20-MHz internal clock source
Up to 10-MHz internal bus operation
0.2% trimmable resolution, 2% deviation over temperature and voltage range
System Protection
Computer operating properly (COP) reset running off bus-independent clock source
Low-voltage detection with reset or stop wakeup
Peripherals
MTIM — 8-bit modulo timer
ACMP — Analog comparator
Full rail-to-rail supply operation
Option to compare to fixed internal bandgap reference voltage
Can operate in stop mode
KBI — Keyboard interrupt ports
Three KBI ports in 6-pin package
Five KBI ports in 8-pin package
Development Support
Background debug system
Breakpoint capability to allow single breakpoint setting during in-circuit debug
Package Options
6-pin dual flat no lead (DFN) package
Two general-purpose input/output (I/O)pins
One general-purpose input pin
One general-purpose output pin
8-pin plastic dual in-line pin (PDIP) package
Four general-purpose input/output (I/O) pins
One general-purpose input pin
One general-purpose output pin
8-pin narrow body SOIC package
Four general-purpose input/output (I/O) pins
One general-purpose input pin
One general-purpose output pin


Innovative HBLED solutions are rapidly gaining popularity in low-cost applications
that require an extremely cost-effective bill-of-materials. However, low-end HBLED
applications still require a high level of system control as well as high constant-current to
maintain color integrity and high light output.
Freescale’s general-purpose ultra-low-end KA2 8-bit MCU offers an economical solution for this application. The on-chip analog comparator is designed to provide an accurate current measurement, which allows feedback control to maintain a constant level in the LED forward current.

KA2 HBLED Demo
Freescale demonstrates its ability to control the HBLED with a KA2 demo unit based on
a buck topology switching power supply.

This maximizes energy transfer between the battery and the HBLED. The KA2 microcontroller is used to measure the current through its on-chip analog comparator, then uses that feedback to control luminosity intensity on the LED. The user can toggle
between two MCU-controlled potential divider settings to vary the LED brightness levels. The demo unit also includes an open-source BDM interface for easy firmware evaluation.

下圖是MC9RS08KA2控制的高亮LED電路圖。