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PDF A6210 Data sheet ( Hoja de datos )
| Número de pieza | A6210 | |
| Descripción | 3A 2MHz Buck-Regulating LED Driver | |
| Fabricantes | Allegro MicroSystems | |
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A6210
3 A, 2 MHz Buck-Regulating LED Driver
Features and Benefits
▪ User-configurable on-time, achieving switching
frequencies up to 2.0 MHz
▪ Brightness control through PWM of DIS pin
▪ Minimal external components required
▪ No output capacitor required
▪ Wide input voltage range: 9 to 46 V
▪ Low 0.18 V sense voltage for higher efficiency
▪ Output Current: up to 3.0 A
▪ Low standby current <100 μA
▪ Thermal shutdown
▪ Supplied in a thermally-enhanced 4 mm QFN package
Applications:
▪ High brightness LEDs
▪ LED driver modules, power supplies and lamps, such as
MR16 and MR11
Package 16-contact QFN (suffix EU):
4 mm × 4 mm × 0.75 mm
Description
The A6210 is a buck regulator that uses valley current-mode
control. This control scheme allows very short switch on-times
to be achieved, making it ideal for applications that require
high switching frequencies combined with high input voltages
and low output LED span voltages.
Low system cost is accomplished through high switching
frequencies of up to 2.0 MHz, allowing smaller and lower value
inductors and capacitors. In addition, few external components
are required through high levels of integration. Optimal drive
circuits minimize switching losses.
The switching frequency is maintained constant, as the on-time
is modulated by the input voltage. This feed-forward control
ensures excellent line correction. The on-time is set by an
external resistor pulled-up to the input supply.
Internal housekeeping and bootstrap supplies are provided
which require the addition of only one small ceramic capacitor.A
top-off charge pump ensures correct operation at light loads.
Internal diagnostics provide comprehensive protection against
input undervoltages and overtemperatures.
The device package is a 16-contact, 4 mm × 4 mm, 0.75 mm
nominal overall height QFN, with exposed pad for enhanced
thermal dissipation. It is lead (Pb) free, with 100% matte tin
leadframe plating.
6210-DS, Rev. 2
VIN
24 V
R1
150 kΩ
C1
1.0 μF
Typical Application
VIN BOOT
LX
TON A 6210
ISEN
PWM or Switch
DIS
SGND
NC GND
C2
22 nF
L1
68 μH
D1
R2
390 mΩ
LED1
LED2
LED3
LED span voltage = 10.5 V
Average LED current = 500 mA
Peak to peak current = 60 mA
Switching frequency = 1.4 MHz
Efficiency = 90.5%
Suggested Parts
Name Description
C1 1 μF, 25V, X5R or X7R ceramic, 1210
C2 22 nF, 50V, X5R or X7R ceramic, 0805
D1 1 A, 30 V, Schottky diode
L1 68 μH, 1 A inductor
R1 180 kΩ, 1%, 0805
R2 390 mΩ, 1%, 0805
Manufacturer - Part Number
Taiyo Yuden, TDK
Taiyo Yuden - NR 6045T 680M
1 page  
A6210
3 A, 2 MHz Buck-Regulating LED Driver
Functional Description
Basic Operation
The A6210 is a buck regulator that utilizes valley current mode
control. The on-time is set by the amount of current that flows
into the TON pin. This is determined by the value of the TON
resistor chosen (R1 in the Functional Block diagram) and the
magnitude of the input voltage, VIN. Under a specific set of
conditions, an on-time can be set that then dictates the switching
frequency. This switching frequency remains reasonably con-
stant throughout load and line conditions as the on-time varies
inversely with the input voltage.
At the beginning of the switching cycle, the buck switch is turned
on for a fixed period that is determined by the current flowing
into TON. Once the current comparator trips, a one-shot mono-
stable, the On Timer, is reset, turning off the switch. The current
through the inductor then decays. This current is sensed through
the external sense resistor (R2), and then compared against the
current-demand signal. After the current through the sense resis-
tor decreases to the valley of the current-demand signal, the On
Timer is set to turn the buck switch back on again and the cycle is
repeated.
Disable/Enable The regulator is enabled by pulling the DIS pin
low. To disable the regulator, the DIS pin can simply be discon-
nected (open circuit).
Shutdown The regulator is disabled in the event of either an
overtemperature event, or an undervoltage on VIN (VINUV) or on
an internal housekeeping supply.
As soon as any of the above faults have been removed and
assuming DIS = 0, the output is restored.
Switch On Time and Switching Frequency The switch
on-time effectively determines the operating frequency of the
converter. To minimize the size of the power inductor and input
filtering it is recommended to run with as high a frequency
as possible. The MOSFET drivers are optimized to minimize
switching losses.
An important consideration in selecting the switching frequency
is to ensure that the on time (60 ns) and off time (350 ns) limita-
tions are not reached under extreme conditions:
• the minimum on time occurs at maximum input voltage
• the minimum off time occurs at minimum input voltage
The following table takes into account the above maximum off
time figure and outlines the typical switching frequencies that can
be achieved for a given number of LEDs and input voltage. Note
that it is highly recommended that worst case values are used
when considering any design.
Switching
Frequency
(MHz)
2.0
1.7
1.0
0.300
12 V
LED
Quantity Span
of LEDs Voltage
(V)
1 3.5
1 3.5
2 7.0
3 10.5
Input Voltage
24 V
Quantity
of LEDs
LED
Span
Voltage
(V)
2 7.0
3 10.5
4 14.0
6 21.0
36 V
Quantity
of LEDs
LED
Span
Voltage
(V)
3 10.5
4 14.0
6 21.0
9 31.5
The switch on time is programmed by the current flowing into
the TON pin. The current is determined by the input voltage, VIN ,
and the resistor, R1. The on time, Ton, can be found:
Ton =
R1
VIN × 2.05 × 1010
+ 10 × 10–9
.
(1)
To calculate the actual switching frequency, fsw, the Ton from the
above calculation can be used in conjunction with the transfer
function of the converter, as follows:
fSW =
VOUT + Vf
VIN + Vf
×
1
Ton
.
(2)
A simplified approach to selecting the Ton resistor (R1), to
accomplish an approximate switching frequency, can be found
from the following formula:
R1 =
VIN × 2.05 × 1010
fSW
.
(3)
Figure 1 illustrates a range of switching frequencies that can be
achieved with a given resistor and LED voltage. Each LED is
assumed to have a voltage drop of 3.5 V.
High Brightness LED Driving
The A6210 can be configured as a very simple, low cost, high
brightness LED driver. The solution can drive high brightness
LEDs up to more than 3 A, while achieving very high efficien-
cies, in excess of 90%.
The solution uses valley current mode control. This architecture
is optimized for high switching frequencies, allowing the use
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
5
5 Page 
A6210
3 A, 2 MHz Buck-Regulating LED Driver
Package EU, 16-Contact QFN
4.00 ±0.15
16
1A
2
4.00 ±0.15
17X D
0.08 C
0.30 ±0.05
0.65
SEATING C
PLANE
0.75 ±0.05
0.40 ±0.10
2
1
B
16
2.70
2.70
16
0.95
1
2
0.35
0.65
2.70 4.10
2.70
4.10
C PCB Layout Reference View
For Reference Only
(reference JEDEC MO-220WGGC)
Dimensions in millimeters
Exact case and lead configuration at supplier discretion within limits shown
A Terminal #1 mark area
B Exposed thermal pad (reference only, terminal #1
identifier appearance at supplier discretion)
C Reference land pattern layout (reference IPC7351
QFN65P400X400X80-17W2M)
All pads a minimum of 0.20 mm from all adjacent pads; adjust as necessary
to meet application process requirements and PCB layout tolerances; when
mounting on a multilayer PCB, thermal vias at the exposed thermal pad land
can improve thermal dissipation (reference EIA/JEDEC Standard JESD51-5)
D Coplanarity includes exposed thermal pad and terminals
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
11
11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet A6210.PDF ] | |
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