DC1217A - Demo Manual

Demo Circuit 1217
QUICK STARTLTC3230
GUIDE
LTC3230
5-LED Main/Sub Display Driver
with Dual LDO
DESCRIPTION
WARNING!
Do not look directly at operating LED.
This circuit produces light that can damage eyes.
Demonstration circuit 1217 is a 5-LED Main/Sub Display
Driver with Dual LDO featuring the LTC3230.
The LTC3230 is a low noise charge pump DC/DC converter designed to drive a four LED Main display and a
one LED Sub display via a single wire interface. The
LTC3230 also contains two 200mA Low Dropout (LDO)
linear regulators, each with three selectable preset output
voltages and independent enable pins.
The charge pump only requires four external capacitors
and the program resistor to form a complete LED power
supply and current controller. The program resistor sets
the maximum LED current. There are 32 dimming
states available for the Main and Sub displays. The
charge pump efficiency is optimized by sensing the voltage across the LED current sources and automatically
switching to 1.5x mode, and subsequently 2x mode,
whenever an LED current source approaches dropout.
Design files for this circuit board are available. Call
the LTC factory.
L, LTC, and LT are trademarks of Linear Technology Corporation. Other product names may
be trademarks of the companies that manufacture the products.
PERFORMANCE SUMMARY Specifications are at TA = 25°C
PARAMETER
Input Supply Range
LDO1 Output Voltage
LDO2 Output Voltage
CPO Output Voltage
CONDITIONS
MIN
2.7
V1 Jumper, JP1 = 1.8V, ENLDO1 Jumper, JP3 = HI, ILOAD <= 200mA
V1 Jumper, JP1 = 1.5V, ENLDO1 Jumper, JP3 = HI, ILOAD <= 200mA
V1 Jumper, JP1 = 1.2V, ENLDO1 Jumper, JP3 = HI, ILOAD <= 200mA
V2 Jumper, JP2 = 3.3V, ENLDO2 Jumper, JP4 = HI, ILOAD <= 200mA, VIN => 3.55V
V2 Jumper, JP2 = 2.8V, ENLDO2 Jumper, JP4 = HI, ILOAD <= 200mA, VIN => 3.05V
V2 Jumper, JP2 = 1.8V, ENLDO2 Jumper, JP4 = HI, ILOAD <= 200mA
1x Mode, ICPO = 0mA
1.5x Mode, ICPO = 0mA
2x Mode, ICPO = 0mA
VIN = 3.6V, ENM = ENS = ENLDO1 = ENLDO2 = LOW
VIN Shutdown Current
LED Current Ratio (ILED/IRSET)
LED Dropout Voltage
VIN = 3.6V, ILED = 15mA
ILED Main/Sub LEDs
RSET = 1.74K, 1 ENM/ENS Strobe (FS)
RSET = 1.74K, 31 ENM/ENS Strobes (FS/31)
TYP
1.8
1.5
1.2
3.3
2.8
1.8
VIN
4.55
5.05
3
545
100
25
0.806
MAX
5.5
UNITS
V
V
V
V
7
μA
A/A
mV
mA
mA
OPERATING PRINCIPLES
The maximum LED currents are set with a 17.4KΩ
resistor for the Main and Sub displays. Current for
each LED is controlled with a precision internal current source driven by a 5-bit linear DAC. The intensity
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LTC3230
of the displays are adjusted by strobing the ENM and
ENS pins. See the LTC3230 data sheet for more information on this process. The DC1217 uses a PIC
micro-controller to interpret commands sent by the
DC590 board via a 2-wire I2C serial interface. The micro-controller then sets the LED displays by strobing
the ENM and ENS pins appropriately. An external
pulse generator may also be used to control the ENM
and ENS pin by setting the ENM Control jumper (JP5)
and ENS Control Jumper (JP6) to external and connecting a pulse generator to the EXT ENM and EXT
ENS terminals.
LDO1 and LDO2 may be enabled by setting the
ENLDO1 jumper (JP3) and the ENLDO2 jumper (JP4)
to the HI position. The LDO output voltages are selected by setting the output voltage jumpers V1 (JP1)
and V2 (JP2) to the desired voltages.
QUICK START PROCEDURE
Demonstration circuit 1217 is easy to set up to evaluate
the performance of the LTC3230. 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 or LDO and GND terminals. See Figure 2 for proper scope probe
technique.
1. Place jumpers in the following positions:
JP1 V1: 1.8V
JP2 V2: 3.3V
JP3 ENLDO1: LO
JP4 ENLDO2: LO
JP5 ENM CONTROL: DC590
JP6 ENS CONTROL: DC590
2. With power off, connect the input power supply to the
VIN and GND terminals.
3. Refer to the DC590 Quick Start guide for QuikEvalTM
setup and software installation details.
4. Make sure the USB cable is connected between the
computer and the DC590 controller board.
5. Connect DC1217 to the DC590 USB Serial Controller using the supplied 14-conductor ribbon cable as
shown in Figure 1.
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6. Turn on the power at the input.
NOTE. Make sure that the input voltage does not exceed 6V.
7. Run the QuikEval program. The program detects the
DC1217 and displays the LTC3230 control window
(shown in Figure 3).
8. Check that the voltages at LDO1 and LDO2 are equal
to 0V.
9. Move the ENLDO1 jumper from the LO position to the
HI position. Check for the proper output voltage, LDO1
= 1.74V to 1.86V
10. Move the ENLDO2 jumper from the LO position to
the HI position. Check for the proper output voltage,
LDO2 = 3.2V to 3.4V
11. Once the proper output voltages are established,
connect and adjust the loads within the operating
range and observe the output voltage regulation, ripple voltage, efficiency and other parameters.
12. Repeat step 12 with the V1 jumper set to 1.5V and
then 1.2V. LDO1 = 1.45V to 1.55V and 1.16V to 1.24V
respectively.
13. Repeat step 12 with the V2 jumper set to 2.8V and
then 1.8V. LDO2 = 2.71V to 2.89V and 1.74V to 1.86V
respectively.
LTC3230
Figure 1. Proper Measurement Equipment Setup
GND
VIN
Figure 2. Measuring Input or Output Ripple
USING THE LTC3230 QUIKEVAL SOFTWARE
The program provides brightness controls for the
Main and Sub LED displays. The UPDATE button
updates the PIC controller with the appropriate
pulse timing information and sets the LED displays
to the current settings on the LTC3230 demo control window. This button must be selected after
power is applied, the DC590 board was disconnected, or the PIC RESET button was depressed.
The LEDS OFF button sets all LEDs to zero and
stops the gradation cycle.
VIEW LTC3230 PRODUCT PAGE Button – This button opens an internet browser and searches the Linear Technology Corporation web site for information
on the LTC3230 when an internet connection is
available.
ENM Control – This vertical slide control adjusts the
Main LEDs from 0 to 25mA in 32 steps. This is ac-
3
LTC3230
complished by clicking on the up or down arrows to
increment by one LSB, by clicking and dragging the
slide pointer, or by clicking in the vertical scroll bar.
The individual LED current and the number of
pulses required to achieve this current are displayed
in the two text boxes below the slider.
ENS Control – This vertical slide control adjusts the
Sub LED from 0 to 25mA in 32 steps. This is accomplished by clicking on the up or down arrows to
increment by one LSB, by clicking and dragging the
slide pointer, or by clicking in the vertical scroll bar.
The individual LED current and the number of
pulses required to achieve this current are displayed
in the two text boxes below the slider.
GRADATION STEP TIME Drop-Down Window – This
window allows the user to select the length of time
for each gradation step while running the
GRADATION Cycle. See GRADATION Cycle button
for more details on this function. The gradation step
time may be adjusted from 10ms to 200ms in various increments.
GRADATION Cycle Button – This button may be selected to start or stop the GRADATION Cycle. The
GRADATION Cycle cycles through the brightness
levels of all the LEDs starting from the lowest to the
highest intensity and then back to the lowest. To
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increase the LED intensity, the enable pins are held
low for 250us prior to the first pulse of each step.
After the highest intensity is reached, the intensity is
then decreased by a single 5us pulse. This decrements the internal counter by one from the previous
setting. This is done until the lowest setting is
reached. This cycle is repeated until the
GRADATION Cycle button is selected again or until
the LEDS OFF button is selected.
UPDATE Button – When this button is selected, the
PIC is updated with the pulse timing and the LED
displays are updated to the present settings on the
LTC3230 control window. This is necessary after
power is applied to the demo board, the ribbon cable has been disconnected, or when the PIC RESET
push button has been depressed.
LEDS OFF Button – This button turns off all of the
LEDs and turns off GRADATION Cycle.
PIC RESET Push Button (SW1) – This button is located on the DC1217 demo board. It Resets the PIC
when depressed. The reset button will not update or
change the demo control window. The UPDATE button on the LTC3230 control window may be used to
update the PIC to the current control window settings.
LTC3230
Figure 3. LTC3230 Control Window
5
LTC3230
6
LTC3230
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