Quick Start Guide for Demonstration Circuits 1071: Main/CAM LED Controller LTC3210-2/LTC3210-3

Description

Demonstration circuit DC1071 is a multi-display LED controller featuring the LTC3210-2 or the LTC3210-3. These devices are low noise charge pumps designed to drive three or four MAIN LEDs and one high current CAM LED. The LTC3210-2/LTC3210-3 require only four small ceramic capacitors and two resistors to form a complete LED power supply and current controller.

The maximum display currents are set using external resistors: a 30.1K ohm resistor for up to 20mA for each Main LED, and a 24.3K ohm resistor for up to 378mA for the CAM display. Current for each LED is precisely controlled by an internal current source. The intensity of the displays is adjusted by strobing the ENM and ENC pins. Refer to the LTC3210-2/LTC3210-3 data sheet for more information on this process.

The DC1071 utilizes a PIC controller to interface between the DC590 board and the LTC3210-2/LTC3210-3 via a 2-wire I²C serial interface. The MAIN display supports 32 dimming states, and the CAM display supports 8 dimming states.

The charge pump optimizes efficiency based on the voltage across the LED current sources. The device powers up in 1X mode and automatically switches to boost mode when any enabled LED current source begins to drop out. The first dropout switches the part to 1.5X mode, and a subsequent dropout switches it into 2X mode. The part resets to 1X mode when shut down.

Design files for this circuit board are available. Contact the Linear Technology factory.

LTC and LT are registered trademarks of Linear Technology Corporation.

Quick Start Procedure

Demonstration circuit 1071 is easy to set up. Refer to the following procedure and Figure 1 for the proper measurement equipment setup.

1. Refer to the DC590 Quick Start guide for QuikEval™ setup and software installation details.
2. Ensure the USB cable is connected between the computer and the DC590 controller board.
3. Connect the DC1071 to the DC590 USB Serial Controller using the supplied 14-conductor ribbon cable, as shown in Figure 1.
4. Attach a 2.9V – 4.5V power source to the Vin and GND turrets of the DC1071 demo board. This provides the Vin power supply for the device. The DC1071 includes an extra 4.7µF de-coupling capacitor between Vin and GND to help accommodate long lead lengths. The DC590 board receives its power from the USB cable.
5. Run the QuikEval™ program. The program detects the DC1071 and displays the LTC3210-2/3 control window (shown in Figure 2).

Figure 1: Proper Measurement Equipment Setup for DC1071A

This diagram illustrates the physical connections required for operating the DC1071 demonstration circuit. It shows the DC1071 demo board connected to the DC590 USB Serial Controller via a 14-conductor ribbon cable. The DC590 controller is connected to a personal computer using a standard USB cable. A power supply providing a voltage between 2.9V and 4.5V is connected to the Vin and GND terminals on the DC1071 board.

Using the LTC3210-2/LTC3210-3 QuikEval Software

The QuikEval software provides controls for adjusting the brightness of the MAIN and CAM LEDs.

• UPDATE Button: This button updates the PIC controller and the LED displays to reflect the current settings shown in the LTC3210-2/LTC3210-3 demo control window. This is useful when power is first applied, after disconnecting the ribbon cable, or after the PIC RESET button is pressed.
• FLASH Button: When selected, this button causes the CAM LED to flash between the ENCT (Torch) setting and the ENCF (Flash) setting for a duration determined by the FLASH TIME drop-down window.
• FLASH TIME Drop-Down Window: Allows the user to select a flash time from 50ms to 1000ms in various increments. This sets the duration the CAM display remains at the ENCF intensity after the FLASH button is released.
• GRADATION Cycle Button: This button starts or stops a cycle that gradually increases and decreases the brightness of the MAIN and CAM LEDs. It illustrates how the LTC3210-2/LTC3210-3 can increment and decrement display intensity.
• LEDS OFF Button: This button turns off all LEDs and stops the GRADATION Cycle.
• VIEW LTC3210-2/3 PRODUCT PAGE Button: Clicking this button opens an internet browser and navigates to the Linear Technology Corporation website for more information on the LTC3210-2/3, provided an internet connection is available.

Control Element Descriptions

ENM Control

This vertical slider adjusts the MAIN display brightness from 0 to 20mA in 32 steps. Adjustment can be made by clicking the [up arrow] or [down arrow] buttons (one LSB per click), clicking in the vertical scroll bar (increments of 4 LSBs), or by clicking and dragging the slide pointer. The individual LED current and the number of pulses required for this current are displayed in two text boxes below the slider.

ENCT Control

This vertical slider adjusts the CAM display intensity from 0 to 162mA in 4 steps. The current is limited in software as some LEDs cannot handle large continuous currents. Intensity adjustment is similar to ENM control: using [up arrow]/[down arrow] buttons, clicking and dragging the pointer, or clicking the scroll bar. The LED current and required pulses are shown in text boxes below.

ENCF Control

This vertical slider sets the CAM display intensity during a flash condition, from 0 to 378mA in 8 steps. When the FLASH button is active, the CAM display illuminates at the ENCF intensity upon mouse button release, for the duration set in the FLASH TIME drop-down. Intensity adjustment methods are the same as ENM/ENCT. The LED flash current and required pulses are displayed in text boxes.

FLASH Button

When selected and released, this button causes the CAM LED to flash at the intensity set by the ENCF control for the period selected in the FLASH TIME drop-down window. This is achieved by holding the ENC pin low for a set PULSE TSD time, then applying pulses on the ENC pin upon mouse button release. After the flash duration, the CAM display returns to the ENCT setting by holding ENC low for a set PULSE TSD time and applying pulses.

FLASH TIME Drop-Down Window

Allows selection of a flash time from 50ms to 1000ms in various increments. This determines how long the CAM display stays at the ENCF setting after the FLASH button is activated.

PULSE TON Drop-Down Window

Allows selection of the pulse ON time for the ENM and ENC pulses. The ON time can be adjusted from 5µs to 20µs in 5µs increments.

PULSE TOFF Drop-Down Window

Allows selection of the pulse OFF time for the ENM and ENC pulses. The OFF time can be adjusted from 5µs to 20µs in 5µs increments.

PULSE TSD (RESET) Drop-Down Window

Allows selection of the pulse TSD time for the ENM and ENC pins. This is the duration the ENM and ENC pins are held low to reset internal counters and DACs before pulses are sent to the enable pins. This time can be adjusted from 250µs to 1000µs in various increments.

GRADATION STEP TIME Drop-Down Window

Allows selection of the duration for each step in the GRADATION Cycle. This time can be adjusted from 50ms to 250ms in various increments.

UPDATE Button

When selected, this button updates the PIC controller with the timing and ENM/ENC information, and refreshes the LED displays to match the current settings in the demo control window.

GRADATION Cycle Button

This button starts or stops the GRADATION Cycle. The cycle progresses through the brightness levels of all LEDs, starting from the lowest to the highest intensity for the Main display, then returning to the lowest. It then cycles through the CAM display intensities, and finally both displays. To increase LED intensity, enable pins are held low for the set PULSE TSD time before each step's pulse. After reaching the highest intensity, it decreases by a low pulse equal to the PULSE TOFF time for each step, decrementing the internal counter until the lowest setting is reached. The cycle repeats until the GRADATION Cycle button is pressed again or the LEDS OFF button is selected.

LEDS OFF Button

This button turns off all LEDs and stops the GRADATION Cycle.

PIC RESET Push Button

Located on the DC1071 demo board, this button resets the PIC microcontroller when depressed. Pressing this button does not update or change the demo control window; the UPDATE button should be used to synchronize the PIC with the current demo control window settings.

Figure 2: LTC3210-2/3 Control Window

This image displays the graphical user interface (GUI) for controlling the LTC3210-2/3 LED controller via the QuikEval software. The window features several control elements:

• ENM Slider: A vertical slider labeled "ENM" controls the Main LED brightness, with a scale indicating current (0 mA to Max).
• ENC TORCH Slider: A vertical slider labeled "ENC TORCH" controls the CAM LED intensity in a non-flashing mode, with a scale indicating current (0 mA to Max).
• ENC FLASH Slider: A vertical slider labeled "ENC FLASH" controls the CAM LED intensity during a flash event, with a scale indicating current (0 mA to Max).
• PULSE TON Input: An input field labeled "PULSE TON" allows setting the pulse ON time, with a default value of 5 µs.
• PULSE TOFF Input: An input field labeled "PULSE TOFF" allows setting the pulse OFF time, with a default value of 5 µs.
• PULSE TSD (RESET) Input: An input field labeled "PULSE TSD (RESET)" allows setting the reset time, with a default value of 250 µs.
• FLASH TIME Input: An input field labeled "FLASH TIME" allows setting the flash duration, with a default value of 100 ms.
• GRADATION STEP TIME Input: An input field labeled "GRADATION STEP TIME" allows setting the duration for each step in the gradation cycle, with a default value of 100 ms.
• UPDATE Button: A button labeled "UPDATE" to apply settings.
• FLASH Button: A button labeled "FLASH" to initiate the CAM LED flash sequence.
• GRADATION START Button: A button labeled "START" within a "GRADATION Cycle" section to begin the brightness gradation.
• LEDS OFF Button: A button labeled "LEDS OFF" to turn off all LEDs.
• Current/Pulses Displays: Sections below the sliders show the current (I ENM, I ENC, I ENC FL) in mA and the number of PULSES, all initialized to 0.
• Product Page Link: A button labeled "VIEW LTC3210-2/3 PRODUCT PAGE" is present.
• Warning Text: A warning about bright LEDs is displayed prominently.

Circuit Diagram Overview

The document includes a detailed schematic diagram illustrating the electronic components and their interconnections for the DC1071 demonstration circuit. This diagram shows the integration of the LTC3210EUD-2/3 LED controller, a PIC16F6301/ST microcontroller, and other support components such as resistors, capacitors, and LEDs. It details the connections for the MAIN LEDs (D1-D4), the CAM LED (D5), and the interfaces for communication with the DC590 controller (ENM, ENC, SDA, SCL) and power supply (Vin, GND).