A6210GEUTR-T Allegro Microsystems Inc, A6210GEUTR-T Datasheet - Page 6

• Manufacturer Part Number: A6210GEUTR-T
• Description: IC LED DRIVER HIGH BRIGHT 16-QFN
• Manufacturer: Allegro Microsystems Inc
• Type: HBLED Driverr

Specifications of A6210GEUTR-T

• Topology: PWM, Step-Down (Buck), Switched Capacitor (Charge Pump)
• Number Of Outputs: 1
• Internal Driver: Yes
• Type - Secondary: High Brightness LED (HBLED)
• Frequency: 100kHz ~ 2 MHz
• Voltage - Supply: 9 V ~ 46 V
• Voltage - Output: 46V
• Mounting Type: Surface Mount
• Package / Case: 16-WSQFN Exposed Pad
• Operating Temperature: -40°C ~ 105°C
• Current - Output / Channel: 3A
• Internal Switch(s): Yes
• Efficiency: 90%
• Led Driver Application: Power Supplies And Lamps
• No. Of Outputs: 1
• Output Current: 3A
• Output Voltage: 46V
• Input Voltage: 9V To 46V
• Dimming Control Type: PWM
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 620-1281-2

A6210
of physically small, low value inductors. An output capacitor is
not necessary either to reduce the ripple current or to close the
control loop.
High efficiencies are achieved via drive circuits optimized to
minimize switching losses and the current sense voltage has a
typical voltage drop of only 183 mV. The current in the LED
string can be pulse width modulated (PWM) via the DIS (Dis-
able/Enable) pin. See figure 4.
The actual current control is maintained on the valley of the cur-
rent ripple. The average LED current is the valley level plus half
the inductor ripple current, as shown in figure 2.
To avoid potential mistriggering issues, it is recommended that
the ripple current that flows through the sense resistor (R2) does
not develop a ripple voltage of less than 20 mV.
The average LED current can be found from:
substituting values:
where:
Figure 1. Switching frequency versus value of external resistor R1 on the
TON pin.
2000
1800
1600
1400
1200
1000
800
600
400
10
4
I
av
=
183 mV
I
av
1 LED
R2
t
on
=
I
=
VALLEY
+
V
V
LED
2 LEDs
IN




+V
1
2
+V
Resistor, R1
+
×
f
f
10
I
V
×
RIPPLE
5
IN
2
f
SW
1
L
–V
(kΩ)
LED
.
×
,
t
on
3 LEDs




4 LEDs
5 LEDs
,
3 A, 2 MHz Buck-Regulating LED Driver
10
6
(4)
(5)
(6)
Figure 2. Current control
Note: V
and sense resistor (R2). The valley current is determined by the
sense voltage (183 mV) divided by the sense resistor.
Worked example
This example uses the brief specification outlined in the typical
application circuit on page 1. The following information is used
as a starting point:
V
3 LEDs producing V
I
LED ripple current, I
The duty cycle can be found initially. Assume the forward voltage
drop of the re-circulation diode is 400 mV, and that the sense
resistor is 183 mV. Then:
One of the objectives is to maximize the switching frequency to
minimize the inductor value. When driving at very high switching
frequencies, the duty cycle may be limited due to the minimum
LED
IN
0
= 24 V ,
= 500 mA, and
f
is the forward voltage drop of the recirculation diode
t
on
t
on
D
+ t
=
off
Valley Current
V
V
= 1/ f
LED
IN
t
LED
RIPPLE
off
+V
+V
SW
f
f
= 12 V ,
=
115 Northeast Cutoff
1.508.853.5000; www.allegromicro.com
Allegro MicroSystems, Inc.
Worcester, Massachusetts 01615-0036 U.S.A.
= 60 mA .
12 + 0.58
24 + 0.58
Time
=
Average
LED Current
0.39
1
/
2
I
RIPPLE
.
(7)
6