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PDF CAT3224 Data sheet ( Hoja de datos )
| Número de pieza | CAT3224 | |
| Descripción | 4 Amp Supercapacitor Flash LED Driver | |
| Fabricantes | ON Semiconductor | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de CAT3224 (archivo pdf) en la parte inferior de esta página. Total 14 Páginas | ||
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CAT3224
4 Amp Supercapacitor Flash LED Driver
www.datasheet4u.com
FEATURES
2 Channels at 2A each in Flash Mode
2 Channels at 200mA each in Torch Mode
Adjustable charge current limit up to 1000mA
Flash/Torch current separate adjustment
Dual-mode 1x/2x charge pump
Dual Cell Supercapacitor Balancing
Flash Safety Timer and Ready Flag
Supercapacitor continuous charging
Shutdown CAP leakage 3µA
“Zero” current shutdown mode
80µA Standby Current (IVIN)
Over-voltage, Over-current Limiting
Thermal Shutdown Protection
Small 3mm x 3mm, 16-pad TQFN package
APPLICATION
High power LED flash
Systems with high peak loads
ORDERING INFORMATION
Part
Number
Package
Package
Marking
CAT3224HV3-GT2 TQFN-16 3 x 3mm(1) JAAT
Note: (1) NiPdAu Plated Finish (RoHS-compliant)
PIN CONFIGURATION
TQFN 16-Pad
(Top View)
DESCRIPTION
The CAT3224 is a very high-current integrated flash
LED driver which also supports the charging function
for a dual-cell supercapacitor applications. Ideal for
Li-ion battery-powered systems, it delivers up to 4A
LED flash pulses, far beyond the peak current
capability of the battery.
Dual-mode 1x/2x charge pump charges the stacked
supercapacitor to a nominal voltage of 5.4V, while an
active balance control circuit ensures that both
capacitor cell voltages remain matched. The nominal
charging current to be drawn from the battery is set
by an external resistor tied to the RC pin.
The driver also features two matched current sources.
External resistors provide the adjustment for the
maximum flash mode current (up to 4A) and the torch
mode current (up to 400mA). A built-in safety timer
automatically terminates the flash pulse beyond a
maximum duration of 300ms.
In addition to thermal shutdown and overvoltage
protection, the device is fully protected against
external resistor programming faults and fully
supports reverse output voltage for all conditions.
The device is packaged in the tiny 16-pad TQFN
3mm x 3mm package with a max height of 0.8mm.
TYPICAL APPLICATION CIRCUIT
16 15 14 13
RF
BAL
CAP
CAP
1
2
3
4
12 RT
11 RC
10 LEDA
9 LEDB
5678
© 2009 SCILLC. All rights reserved.
Characteristics subject to change without notice
1
Doc. No. MD-5043, Rev. A
1 page  
CAT3224
TYPICAL CHARACTERISTICS
VIN = 3.6V, C = 0.55F, TAMB = 25ºC, typical application circuit unless otherwise specified.
Idle Quiescent Current vs. Input Voltage
Charge Current vs. RC
www.datasheet4u.com 100
1.0
90
80
70
60
3.0
3.5 4.0 4.5 5.0
INPUT VOLTAGE [V]
5.5
Flash LED Current vs. RF
10.0
0.1
0.1
1
RC[kΩ]
10
Torch LED Current vs. RT
1000
1.0 100
0.1
0.1
1
RF [kΩ]
10
FLAG RDSON vs. Input Voltage
20
15
10
5
0
3.0
3.5 4.0 4.5 5.0
INPUT VOLTAGE [V]
5.5
© 2009 SCILLC. All rights reserved.
Characteristics subject to change without notice
5
10
0.1
1
RT [kΩ]
10
Doc. No. MD-5043 Rev. A
5 Page 
Capacitor Selection
The supercapacitor size depends on the flash
requirement including flash duration, LED current
and LED forward voltage. The minimum supercapa-
citor value is calculated as follows.
www.datasheet4Cu.c=om
IOUT × TFLASH
( )VCAP − IOUT RCAP−ESR + RLEDAB − VF
where VCAP is the initial CAP voltage (5.2V typical), and
VF is the LED forward voltage. Any interconnection
parasitic resistance is assumed negligible in the
calculation.
For example, for a 4A flash with 0.1s duration and
3.1V LED VF, the minimum capacitor value is:
C
=
5.2V
−
4A × 0.1s
4A(0.1Ω + 0.1Ω) −
3.1V
≅
0.3F
To support 4A flash pulses, we recommend using
the 0.55F supercapacitor HS206F from CAP-XX with
a voltage rating of 5.5V and a low ESR of 85mΩ.
In addition to the supercapacitor, a small 1μF
ceramic capacitor is recommended on the CAP
output in order to filter out the charge pump
switching noise due to the ESR of the
supercapacitor.
If a single cell supercapacitor is used, it is
recommended to connect a small 1μF ceramic
capacitor between the BAL pin and GND. This will
prevent any oscillation on the BAL pin and keep the
quiescent current low.
CAT3224
Thermal Dissipation
Thermal dissipation occurs in the CAT3224 device
due to the high current flowing in charge mode, as
well as in torch or flash mode. During charge mode,
in case the input voltage is high and the driver
operates in 2x charge pump mode, the power
dissipation may increase significantly. In torch and
flash modes, the power dissipation is proportional to
the difference between the CAP and LEDA/B pin
voltages. If the junction temperature exceeds 150ºC
typical, the device goes into thermal shutdown mode
and resumes normal operation as soon as the
temperature drops by about 20ºC. To improve the
thermal performance, the TQFN exposed pad
should be connected to the PCB ground plane
underneath.
Recommended Layout
The ground side of the three current setting
resistors, RC, RT, RF, should be star connected back
to the GND of the PCB. In charge pump mode, the
driver switches internally at a high frequency.
Therfore it is recommended to minimize trace length
to all four capacitors. A ground plane should cover
the area under the driver IC as well as the bypass
capacitors. Short connection to ground on capacitors
CIN and COUT can be implemented with the use of
multiple via. A copper area matching the TQFN
exposed pad (TAB) must be connected to the
ground plane underneath with a via.
In order to minimize the IR drop in flash mode, the
traces between the supercapacitor and the CAP
pins, and between LEDA/LEDB pins and the LED(s)
shout be kept as short as possible and wide enough
to handle the high current peaks. The
supercapacitor negative terminal and the LED
cathodes need to be connected to the ground plane
directly.
© 2009 SCILLC. All rights reserved.
Characteristics subject to change without notice
11
Doc. No. MD-5043, Rev. A.
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet CAT3224.PDF ] | |
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