Analog Devices DC2575A Demo Manual page 2

DEMO MANUAL DC2575A
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Table 1. Typical Performance Summary for DC2575A (LT8391A)
PARAMETER
Input Voltage PV Range
IN
Switching Frequency (f )
SW
Spread Spectrum (SSFM) Frequency Range
I
LED
V range
LED
Open LED Voltage V
OUT
Typical Efficiency (100% PWM DC)
Internally-Generated PWM Dimming Range
Internally-Generated PWM Dimming Frequency
Peak Switch Current Limit Boost Region
Peak Switch Current Limit Buck Region
PV Undervoltage Lockout (UVLO) falling
IN
PV Enable Turn-On (EN) Rising
IN
Demonstration circuit 2575A is easy to set up to evaluate
the performance of the LT8391A. Follow the procedure
below:
1. With power off, connect a string of LEDs that will run
with forward voltage less than or equal to 16V (at
+
1.5A) to the LED and LED
as shown in Figure 1.
2. Connect the EN/UVLO terminal to GND.
3. Set JP2 to EXT/ON and JP3 to ON for 100% always-
on LED operation. Set JP1 to NO SSFM/SYNC to run
without SSFM.
4. With power off, connect the input power supply to the
PV and GND banana jacks. Make sure that the DC
IN
input voltage will not exceed 60V.
5. Turn the input power supply on and make sure the
voltage is between 4V and 60V for proper operation.
6. Release the EN/UVLO-to-GND connection.
2
CONDITIONS
Operating V ≤16V
LED
R3 = 59.0k, JP1 = NO SSFM/SYNC
JP1 = SSFM ON
R2 = 0.056Ω 7.0V < PV
R9 = 90.9k, R10 = 113k
R5 = 1M, R6 = 54.9k
R5 = 1M, R6 = 54.9k
PV = 13V, V = 16V, I
IN LED
JP2 = INT, JP3 = INT
JP2 = INT, JP3 = INT R30 = 301k, R3 = 59.0k
R1 = 0.006Ω
R1 = 0.006Ω
R7 = 383k, R8 = 165k
R7 = 383k, R8 = 165k
–
banana jacks on the PCB
MIN
< 60V V ≤16V
IN LED
4.8V
= 1.5A
LED
1/128
7. Observe the LED string running at the programmed
LED current.
8. To change the brightness with analog dimming, sim-
ply attach a voltage source to either the CTRL1 or
CTRL2 terminal and set the voltage between 0V and
1.5V. See data sheet for details.
9. To change brightness with external PWM dimming,
set JP2 to EXT/ON and JP3 to EXT. Attach a 3V rect-
angular waveform with varying duty cycle to the PWM
terminal.
10. To change brightness with internally-generated PWM
dimming, set JP2 to INT and JP3 to INT. Adjust the
setting of the VR1 variable resistor with a small flat-
head screwdriver to toggle between 0% and 100%
PWM dimming duty cycle in 1/128 steps.
11. To enable spread spectrum frequency modulation, set
JP1 to SSFM ON.
TYP
4V
2.0MHz
f
SW
1.5A
18.2V
92%
488Hz
8.3A
8.3A
4.3V
5.1V
MAX
60V
f • 1.25
SW
16V
100%
Rev. A