A8514KLPTR-T Allegro Microsystems Inc, A8514KLPTR-T Datasheet - Page 16

• 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

Figure 12. Percentage Error of the LED current versus PWM duty cycle
(at 200 Hz PWM frequency).
A8514
Another important feature of the A8514 is the PWM signal to
LED current delay. This delay is typically less than 500 ns, which
allows greater accuracy at low PWM dimming duty cycles, as
shown in figure 12.
APWM pin
The APWM pin is used in conjunction with the ISET pin (see fig-
ure 13). This is a digital signal pin that internally adjusts the ISET
current. When this pin is not used it should be tied to ground.
The typical input signal frequency is between 20 kHz and 1 MHz.
Figure 14. Output current versus duty cycle; 200 kHz APWM signal.
10
8
6
4
2
0
0.1
80
70
60
50
40
30
20
10
0
0
20
PWM Duty Cycle, D (%)
1
I
OUT
= 65 mA
APWM Duty Cycle (%)
40
I
OUT
60
10
= 80 mA
Worst-case
Typical
80
Wide Input Voltage Range, High Efficiency
100
100
The duty cycle of this signal is inversely proportional to the per-
centage of current that is delivered to the LEDs (figure 14).
To use this pin for a trim function, the user should set the maxi-
mum output current to a value higher than the required current by
at least 5%. The LED I
appropriate value. Another consideration that also is important
is the limitation of the user APWM signal duty cycle. In some
cases it might be preferable to set the maximum I
25% to 50% higher, thus allowing the APWM signal to have duty
cycles that are between 25% and 50%.
Figure 13. Simplified block diagram of the APWM and ISET circuit.
Figure 15. Percentage Error of the LED current versus PWM duty cycle;
200 kHz APWM signal.
12
10
R
8
6
4
2
0
ISET
0
Fault Tolerant LED Driver
APWM
ISET
PWM
20
SET
current is then trimmed down to the
115 Northeast Cutoff
1.508.853.5000; www.allegromicro.com
Allegro MicroSystems, Inc.
Worcester, Massachusetts 01615-0036 U.S.A.
Current
Mirror
ISET
APWM Duty Cycle (%)
40
I
OUT
I
OUT
= 80 mA
60
= 65 mA
Current
Adjust
Driver
LED
80
SET
A8514
current to be
100
16