DC1265A-B - ANALOG DEVICES - Datasheet.Directory

LTC3220/LTC3220-1

DESCRIPTION

WARNING!

Do not look directly at operating LED.

This circuit produces light that can damage eyes.

Demonstration circuit 1265 is a 360mA Universal 18-

Channel LED Driver with twelve white LEDs and two RGB

LEDs featuring the LTC3220/LTC3220-1.

The LTC3220/LTC3220-1 is a low noise charge pump

designed to drive 18 universal LED (ULED) current

sources. The LTC3220/LTC3220-1 requires only five

small ceramic capacitors to form a complete LED power

supply and current controller.

The maximum display currents are set with an internal

precision current reference. On/Off blinking, gradation,

intensity, and a software controlled shutdown are ac-

complished via an I

C serial interface. See the

LTC3220/LTC3220-1 data sheet for more information on

this process. There are 64 dimming states available for

the universal LEDs.

The charge pump optimizes efficiency based on the volt-

age across the LED current sources. The part powers up

in 1x mode and will automatically switch to boost mode

whenever any enabled LED current source begins to drop

out. The first dropout switches the part to 1.5x mode and

a subsequent dropout switches the part into 2x mode.

The part resets to 1x mode whenever a data byte is up-

dated via the I

C port.

Design files for this circuit board are available. Call

the LTC factory.

L, LTC, LTM, LT are registered trademarks of Linear Technology Corporation. Other product

names may be trademarks of the companies that manufacture the products.

PERFORMANCE SUMMARY

Specifications are at T

= 25°C

PARAMETER CONDITIONS MIN TYP MAX UNITS

Input Supply Range (V

)

2.9 5.5

VIN Shutdown Current 3.2 7 u

Operating Voltage 1.5 5.5

Shutdown Current 1 μ

CPO Regulation Voltage 1.5x Mode, I

CPO

= 20mA

2x Mode, I

CPO

= 20mA

4.5

5.03

Full-Scale LED Current ULED = 1V 18 20 22 m

Absolute Maximum LED Current Strong GPO Mode, external current limit needed 25 m

Minimum (I

LSB

) LED Current Step

0.314 m

Minimum Programmable Current ULED Data Register Programmed to 0b00000001 0.395 m

LED Current Matching Any Two Outputs, 50% Full-Scale

1.5 %

LED Dropout Voltage I

LED

= Full-Scale

120 m

LED Turn-on Delay From Stop Bit, Part Enabled

4 uS

Demo Circuit 1265

QUICK START GUIDE

LTC3220/LTC3220-1

360mA Universal 18-Channel

LED Driver

LTC3220/LTC3220-1

QUICK START PROCEDURE

Demonstration circuit 1265 is easy to set up to evaluate

the performance of the LTC3220/LTC3220-1. Refer to

Figure 1 for proper measurement equipment setup and

follow the procedure below:

NOTE.

When measuring the input or output voltage ripple, care

must be taken to avoid a long ground lead on the oscilloscope

probe. Measure the input or output voltage ripple by touching the

probe tip directly across the VIN and GND or CPO and GND

terminals. See Figure 2 for proper scope probe technique.

Refer to the DC590 Quick Start Guide for QuikEval

setup and software installation details.

Make sure the USB cable is connected between the

computer and the DC590 controller board.

NOTE.

If using the DC590B board, a specific DVCC voltage level

may be selected. This is done by setting the VCCIO jumper on the

DC590 board to one of the following settings: 3.3V, 5V, removed

for 2.7V or set to external if an external supply is desired to be

used.

Connect DC1265 to the DC590 USB Serial Controller

using the supplied 14-conductor ribbon cable as

shown in Figure 1.

With power off, connect a 5V, 1A power supply to VIN

and GND with a series ammeter and a voltmeter as

shown in Figure 1.

Turn on and set the input power supply between 2.9 –

5.5V. The DC1265 has an extra 4.7uF de-coupling ca-

pacitor between VIN and GND to help accommodate

long VIN source lead lengths. The DC590 board gets

its power from the USB cable.

NOTE.

Make sure that the input voltage does not exceed 6V.

Run the QuikEval program. The program detects the

DC1265 and displays the LTC3220 control window

(shown in Figure 5).

LTC3220/LTC3220-1

Figure 1.

Proper Measurement Equipment Setup

VIN

GND

Figure 2.

Measuring Input or Output Ripple

LTC3220/LTC3220-1

USING THE LTC3220 QUIKEVAL SOFTWARE

through

U18

vertical sliders control the intensity for

associated ULED outputs from 0 to 20mA in 64 steps

when the AUTO SET ULEDs button is active or when the

SET SELECTED ULEDs, BLINK ULEDs, or other ULED

control buttons are selected. The ULED intensity slider

may be adjusted by clicking on the up or down arrows to

increment or decrement by one LSB or by clicking and

dragging the slide pointer. The hex code is displayed in

the box below the slider.

The LTC3220 program provides brightness controls, al-

lows the user to gradate the LEDs up or down, and blink

at a selected on-time and period. A software controlled

shutdown bit allows the user to go into shutdown and

return to the previous state at any time. The

LTC3220/LTC3220-1 also has an external reset pin which

resets all the internal registers and puts the part into

shutdown. The intensity of the LEDs may be set by se-

lecting the AUTO SET ULEDs button (green when se-

lected) and then setting the intensity in the associated

vertical slider.

SET SELECTED ULEDs

button sets all selected LEDs to

the chosen intensity settings.

LTC3220/LTC3220-1

select

button selects between the

LTC3220 and the LTC3220-1 I

C address to drive demo

boards with either the LTC3220 (DC1265A-A) or the

LTC3220-1 (DC1265A-B). If the button is not selected to

the correct address and an Acknowledge is not received,

an Error message box pops up as shown in Figure 3.

Select OK to return to the program to correct the prob-

lem or select Cancel to quit the program.

AUTO SET ULEDs

button is green when activated. When

a ULED vertical slider is changed while this button is ac-

tivated, the associated LED immediately updates. When

this button is not activated (yellow), the SET SELECTED

ULEDs, BLINK ULEDs, GPO MODE, or one of the grada-

tion buttons must be used to set or change the LED in-

tensity.

SELECT ALL

selects all ULED outputs to change when

the SET SELECTED ULEDs, CLEAR SELECTED ULEDs, or

other ULED control buttons are selected.

DESELECT ALL

deselects all selected ULED outputs and

prevents the ULED outputs from changing intensity or

modes when the SET SELECTED ULEDs, CLEAR

SELECTED ULEDs, or other ULED control buttons are

selected. The ULED intensity will still change when the

AUTO SET ULEDs button is activated.

Figure 3.

Acknowledge not received Error Message Box

QUICK WRITE

button uses the LTC3220/LTC3220-1

Quick Write feature to set all LEDs to the same intensity

and mode as ULED1. The intensity of ULED1 is updated

to the value indicated on the U1 vertical slider. All vertical

sliders and register text boxes on the LTC3220 Control

Window are updated to match the IC settings. The U1

select button does not need to be selected for this button

to work.

VIEW LTC3220 PRODUCT PAGE

button opens an inter-

net browser and searches the Linear Technology Corpo-

ration web site for information on the LTC3220 when an

internet connection is available.

REG0

through

REG19

text box windows display the

hexadecimal value that has been written to the corre-

sponding registers of the selected LTC3220/LTC3220-1.

These values are updated when the LTC3220/LTC3220-1

button is selected to show what was written last to the

associated part.

INTENSITY TRACKING

button adjusts the vertical sliders

U2-U18 to the same setting as vertical slider U1 when

the U1 vertical slider is changed with the Intensity Track-

ing button is selected.

through

U18

select buttons (located above the verti-

cal sliders) are used to individually select or deselect the

modes or intensity of the ULED outputs.

LTC3220/LTC3220-1

CLEAR SELECTED ULEDs

button turns off and clears the

GRADATION TIME

option buttons set the desired time to

gradate up to or down from the selected ULED intensity

when the GRADATE UP or GRADATE DOWN buttons are

selected. If the DISABLED option button is selected, the

ULED outputs will not gradate when any of the

GRADATION control buttons are selected.

GRADATE UP

button gradates the selected ULED outputs

up to the desired intensity and disables gradation when

done. The associated ULED select button above the verti-

cal slider is highlighted purple to indicate that gradation

mode has been enabled.

GRADATE DOWN

button gradates the selected ULED

outputs down from the set intensity and disables grada-

tion when done. The associated ULED select button

above the vertical slider is highlighted purple to indicate

that gradation mode has been enabled.

BLINK ONt/PERIOD

option buttons set the desired blink-

ing on-time and period to blink after the BLINK ULEDs

button has been selected.

BLINK ULEDs

button blinks or stops blinking the se-

lected ULED outputs at the on-time and period selected

by the BLINK ONt/PERIOD option buttons and at the se-

lected ULED intensity. The associated ULED select button

above the vertical slider is highlighted green to indicate

that blink mode has been enabled.

CHARGE PUMP MODE

option buttons allow the user to

select between Auto switching (not forced to any mode),

Force 1x, Force 1.5x, and Force 2x charge pump modes.

GPO MODE

button disables or enables dropout for the

selected ULED outputs. When dropout is disabled the

ULED output will not cause the charge pump to switch

into 1.5x or 2x modes and the pin may be used as a gen-

eral-purpose output (GPO).

When GPO mode is initiated with a ULED intensity value

greater than 0, then the Current Limited GPO Mode is

set. The GPO is current limited to the current set with

the associated vertical slider. The associated ULED select

button above the vertical slider is highlighted orange to

indicate that GPO mode has been initiated.

If GPO is initiated with the ULED intensity set to 0, then

the Strong Pull-Down GPO Mode is set. The Strong Pull-

Down mode is not current limited and only consumes

3uA of quiescent current per GPO. When this mode is

invoked a pop-up window warns the user that a current

limit resistor is needed to prevent the current from ex-

ceeding 25mA as shown in Figure 4. Select OK to con-

tinue into Strong GPO Mode or Cancel to return to the

program without setting the ULED output to Strong GPO

Mode.

NOTE.

When Strong GPO mode is used, the LED should be removed and

a current limiting resistor should be installed to make sure that the

current does not exceed the Absolute Maximum rated current. Since CPO

is limited by a weak pull-up during shutdown, CPO should not be used as

source to any output in Strong GPO mode during shutdown.

Figure 4.

Strong GPO Mode Warning Message Box

UPDATE ALL REG

button updates the data registers to

the data displayed in the register text boxes.

/RESET

button resets all internal registers using the ex-

ternal /RST pin when this button is not set (red). When

this button is set (green) then the /RESET button is set to

DVCC.

SHUTDOWN

button, when set (red), sets the

SHUTDOWN bit in the command register and puts the

LTC3220 into shutdown. When this button is not set

(green), it clears the SHUTDOWN bit in the command

DEMO 1

button

may be selected to start or stop Demo 1.

Demo 1 cycles through some of the colors that the RGB

LEDs can produce using the LTC3220/LTC3220-1’s gra-

dation feature. Once the RGB color demo is complete,

the demo then blinks the two RGB LEDs and gradates up

the white LEDs two at time. Then all LEDs are set to blink

together using the Quick Write feature. Lastly, all LEDs

are gradated up and down together prior to repeating the

entire sequence.

LTC3220/LTC3220-1

Figure 5.

LTC3220 Control Window

LTC3220/LTC3220-1