A8514KLPTR-T Allegro Microsystems Inc, A8514KLPTR-T Datasheet - Page 15

• Manufacturer Part Number: A8514KLPTR-T
• Description: IC LED DVR WHT 4X80MA 16-ETSSOP
• Manufacturer: Allegro Microsystems Inc

Specifications of A8514KLPTR-T

• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

A8514
LED current setting and LED dimming
The maximum LED current can be up to 80 mA per channel,
and is set through the ISET pin. To set the I
a resistor, R
following formula:
where I
rent through the LEDs, referred to as the 100% current. Standard
R
PWM dimming
The LED current can be reduced from the 100% current level
by PWM dimming using the PWM/EN pin. When the PWM/EN
pin is pulled high, the A8514 turns on and all enabled LEDs sink
100% current. When PWM/EN is pulled low, the boost converter
and LED sinks are turned off. The compensation (COMP) pin is
floated, and critical internal circuits are kept active. The typical
PWM dimming frequencies fall between 200 Hz and 1 kHz. Fig-
ures 11A to 11D provide examples of PWM switching behavior.
Figure 11A. Typical PWM diagram showing V
well as the PWM signal. PWM dimming frequency is 500 Hz at 50% duty
cycle; shows V
5 V/div.), and I
C2
C1
C3
C4
ISET
values, at gain equals 653, are as follows:
Standard Closest R
LED
Resistor Value
is in A and R
ISET
LED
OUT
10.2
16.5
22.1
(kΩ)
, between this pin and ground, according to the
8.25
(ch4, 50 mA/div.), time = 500 μs/div.
(ch1, 10 V/div.), COMP (ch2, 2 V/div.), PWM (ch3,
R
ISET
ISET
ISET
= (1.003 × 653) / I
COMP
V
PWM
OUT
I
LED
is in Ω. This sets the maximum cur-
t
LED current per LED, I
OUT
, I
LED
LED
LED
(mA)
current, connect
80
65
40
30
, and COMP pin as
Wide Input Voltage Range, High Efficiency
LED
(2)
Figure 11B. Typical PWM diagram showing V
well as the PWM signal. PWM dimming frequency is 500 Hz at 1% duty
cycle ; shows V
5 V/div.), and I
Figure 11C. Delay from rising edge of PWM signal to LED current; shows
PWM (ch1, 2 V/div.), and I
Figure 11D. Delay from falling edge of PWM signal to LED current turn off;
shows PWM (ch1, 2 V/div.), and I
C1
C2
C1
C3
C4
C2
C1
C2
LED
Fault Tolerant LED Driver
OUT
(ch4, 50 mA/div.), time = 500 μs/div.
(ch1, 10 V/div.), COMP (ch2, 2 V/div.), PWM (ch3,
COMP
PWM
LED
V
I
LED
OUT
(ch2, 50 mA/div.), time = 200 ns/div.
115 Northeast Cutoff
1.508.853.5000; www.allegromicro.com
Allegro MicroSystems, Inc.
Worcester, Massachusetts 01615-0036 U.S.A.
LED
t
t
t
PWM
PWM
I
(ch2, 50 mA/div.), time = 200 ns/div.
LED
I
LED
OUT
, I
LED
, and COMP pin as
15