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CAT3224 4 Amp Supercapacitor Flash LED Driver
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 4 A 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 5.4 V, 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 4 A) and the torch mode current (up to 400 mA). A built-in safety timer automatically terminates the flash pulse beyond a maximum duration of 300 ms. 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 3 mm x 3 mm package with a max height of 0.8 mm.
Features
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TQFN-16 HV3 SUFFIX CASE 510AD
PIN CONNECTIONS
GND VIN CN CP
RF BAL CAP CAP
1
RT RC LEDA LEDB
TORCH
CHRG
* * * * * * * * * * * * * * *
2 Channels at 2 A Each in Flash Mode 2 Channels at 200 mA Each in Torch Mode Adjustable Charge Current Limit up to 1000 mA 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 3 mA "Zero" Current Shutdown Mode 80 mA Standby Current (IVIN) Over-voltage, Over-current Limiting Thermal Shutdown Protection Small 3 mm x 3 mm, 16-pad TQFN Package This Device is Pb-Free, Halogen Free/BFR Free and RoHS Compliant
(Top View)
MARKING DIAGRAM
JAAT
JAAT = Specific Device Code
ORDERING INFORMATION
Device Package Shipping 2,000/ Tape & Reel CAT3224HV3-GT2 TQFN-16 (Pb-Free)
Note: NiPdAu Plated Finish (RoHS-compliant)
Applications
* High Power LED Flash * Systems with High Peak Loads
(c) Semiconductor Components Industries, LLC, 2009
December, 2009 - Rev. 0
1
FLASH
Publication Order Number: CAT3224/D
FLAG
CAT3224
1 mF VIN (2.5 V to 5.5 V) 1 mF VIN CAT3224 FLAG CHRG FLASH TORCH RC RF 826 W 261 W RT CP CN CAP CAP BAL LEDA LEDB GND 562 W GND 2A 2A - Dual-Cell Supercapacitor 1 mF + 0.55 F
Figure 1. Typical Application Circuit Table 1. ABSOLUTE MAXIMUM RATINGS
Parameter VIN, RC, RF, RT voltage CAP, CP, CN voltage CHRG, FLASH, TORCH, FLAG voltage (Note 1) BAL, LEDA, LEDB Storage Temperature Range Junction Temperature Range Lead Temperature ESD Rating HBM (Human Body Model) ESD Rating MM (Machine Model) Rating GND-0.3 to 6 GND-0.3 to 7 GND-0.3 to 6 GND-0.3 to CAP+0.3 -65 to +160 -40 to +150 300 2000 200 Unit V V V V _C _C _C V V
Stresses exceeding Maximum Ratings may damage the device. Maximum Ratings are stress ratings only. Functional operation above the Recommended Operating Conditions is not implied. Extended exposure to stresses above the Recommended Operating Conditions may affect device reliability.
Table 2. RECOMMENDED OPERATING CONDITIONS
Parameter VIN Ambient Temperature Range LEDA, LEDB current (in flash mode) LEDA, LEDB current (in torch mode) Input Current Limit FLAG pull-up resistor current LED Forward Voltage Range (Vf) Rating 2.0 to 5.5 -40 to +85 up to 2 10 to 200 up to 1 0 to 10 1.3 to 4.2 Unit V _C A mA A mA V
Table 3. PACKAGE THERMAL IMPEDANCE
Parameter TQFN 3 mm x 3 mm 16-Lead qJA (Note 2) Range 42 Unit _C/W
Table 4. PACKAGE TRANSIENT THERMAL IMPEDANCE
Parameter TQFN 3 mm x 3 mm 16-Lead Transient qJA (Note 3) (100 ms pulse) Range 7 Unit _C/W
1. Pins can be driven above VIN with no leakage current or change in operation. 2. qJA (Junction to Ambient thermal resistance) is calculated with 2 square inches of copper connected to package exposed pad. 3. Transient qJA is calculated for a 100 ms pulse at 5 watts with 2 square inches of copper connected to package exposed pad.
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CAT3224
Table 5. ELECTRICAL OPERATING CHARACTERISTICS (VIN = 3.6 V, EN = 1.3 V, TAMB = 25C unless otherwise stated.)
Symbol IQVIN IQCAP Name Quiescent Current on VIN pin (IIN - 2 x IOUT) Quiescent Current on CAP pin Conditions CAP Charged & idle CAP Charging 2x Mode CAP Charged & idle Shutdown mode Shutdown, VIN = 0 V IQSHDN GFLASH GTORCH GCHARGE VRX IRX_MAX IIN_MAX VC_OFF VC_HYST VF_ON VF_HYST RLEDAB RCP FOSC TFLASH VFLAG REN VEHI VELO VBAL TSD THYS VUVLO Shutdown Current Flash Gain (IFLASH / IRF) Torch Gain (ITORCH / IRT) Input Current Limit Gain (ICHRG / IRC) RSET Regulated Voltage (VRF VRT VRC) Rset Current limit (IRF IRT IRC) Input current limit in charge mode CAP Charge off voltage CAP Charge Hysteresis CAP voltage FLAG pulled low CAP voltage FLAG Hysteresis LEDA/B Combined Dropout Resistance Charge Mode Resistance IFLASHAB = 4 A 1x mode 2x mode, VIN = 3.5 V Charge Pump Frequency Flash Timeout Duration Flag low voltage threshold (Open Drain) CHRG, FLASH, TORCH Pin Internal Pull-down Resistor Logic High Level Logic Low Level Active Balance Control (VCAP / 2) Thermal Shutdown Thermal Hysteresis Undervoltage lockout (UVLO) threshold 5 mA Load on BAL FLAG Driven low 100 mA pull-up 150 1.3 0.4 -2 150 20 1.9 +2 CHRG = FLASH = TORCH = 0 V IFLASH = 2 A ITORCH = 200 mA ICHARGE = 400 mA IRX = 0.1 mA VRX = 0 V VRC = 0 V RC = 2 kW 0.59 900 120 400 0.6 3.5 1.4 5.4 0.2 5.2 0.2 110 2 4 800 300 0.2 0.61 V mA A V V V V mW W W kHz ms V kW V V % C C V Min Typ 80 6 10 3 3 1 Max Units mA mA mA mA mA mA
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CAT3224
Cap Voltage and Flag Output The timing diagram in Figure 2 shows the CAP output voltage and the FLAG output in charge mode (with CHRG input high).
CAP VOLTAGE
VC OFF VC HYST VF ON VF HYST
TIME
Charge Current 0A
FLAG
FLASH
LED Current 0A
Figure 2. Supercapacitor Charge Timing Diagram
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CAT3224
TYPICAL CHARACTERISTICS
(VIN = 3.6 V, C = 0.55 F, TAMB = 25C, typical application circuit unless otherwise specified.) 100 1.0
90 ICHARGE (A) 3.0 3.5 4.0 4.5 5.0 5.5 0.1 0.1 IQVIN (mA)
80
70
60
1.0 RC (kW)
10
INPUT VOLTAGE (V)
Figure 3. Idle Quiescent Current vs. Input Voltage
10 1,000
Figure 4. Charge Current vs. RC
ITORCH (mA) 0.1 1.0 RF (kW) 10
IFLASH (A)
1.0
100
0.1
10
0.1
1.0 RT (kW)
10
Figure 5. Flash LED Current vs. RF
20
Figure 6. Torch LED Current vs. RT
15 RDSON (W)
10
5
0
3.0
3.5
4.0
4.5
5.0
5.5
INPUT VOLTAGE (V)
Figure 7. FLAG RDSON vs. Input Voltage
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CAT3224
TYPICAL CHARACTERISTICS
(VIN = 3.6 V, C = 0.55 F, TAMB = 25C, typical application circuit unless otherwise specified.) 630 620 610 600 590 580 570 VRC (mV) 0 0.5 1.0 IFLASH (A) 1.5 2.0 VRF (mV) 630 620 610 600 590 580 570 0 0.2 0.4 0.6 0.8 1.0
ICHARGE (A)
Figure 8. VRF vs. IFLASH
630 620 5.5 VC_OFF (V) 610 VRT (mV) 600 590 580 570 4.0 6.0
Figure 9. VRC vs. ICHARGE
5.0
4.5
0
50
100 ITORCH (mA)
150
200
0
0.5
1.0
1.5 RC (kW)
2.0
2.5
3.0
Figure 10. VRT vs. ITORCH
500 400 300 200
Figure 11. VCAP idle vs. RC
IOUT (mA)
Vled = 2.9 V 100 0
3.0
3.5
4.0 VCAP (V)
4.5
5.0
5.5
Figure 12. Torch Output Current vs. VCAP
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CAT3224
TYPICAL CHARACTERISTICS
(VIN = 3.6 V, C = 0.55 F, TAMB = 25C, typical application circuit unless otherwise specified.)
CHRG 5V/div
CHRG 5V/div
CAP 2V/div Input Current 1A/div 1s/div
CAP 2V/div Input Current 500mA/div 2s/div
Figure 13. Charge Cycle, 1 A Input Current
Figure 14. Charge Cycle, 500 mA Input Current
CHRG 5V/div
FLASH 5V/div
CAP 2V/div Input Current 500mA/ div
LED Current 1A/div
4s/div
40 ms/div
Figure 15. Charge Cycle, 300 mA Input Current
Figure 16. FLASH Transient Response
CHRG 5V/div Input Current 500mA/div CAP 2V/div FLAG 5V/div 2s/div
Figure 17. Charge Cycle with FLAG
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CAT3224
Table 6. PIN DESCRIPTION
Pin # 1 2 3, 4 5 6 7 8 9 10 11 12 13 14 15 16 TAB Name RF BAL CAP CHRG FLASH TORCH FLAG LEDB LEDA RC RT VIN CP CN GND TAB Flash Current Setting Resistor terminal Active Supercapacitor Balance Control Supercapacitor Positive Connection Charge Supercapacitor Enable Flash Enable Torch Enable Flash Ready Flag output, Open drain (Active low) LED B channel anode (+) connection LED A channel anode (+) connection Charge Current Setting Resistor terminal Torch Current Setting Resistor terminal Positive supply connection to battery Bucket capacitor Positive terminal Bucket capacitor Negative terminal Device ground connection Connect to GND on the PCB Function
Pin Function VIN is the supply pin for the device and for the supercapacitor charger circuit. A small 1 mF ceramic bypass capacitor is required between the VIN pin and ground near the device. GND is the ground reference for the charge pump. This pin must be connected to the ground plane on the PCB. TAB is the exposed pad underneath the package. For best thermal performance, the tab should be soldered to the PCB and connected to the ground plane. CAP is the positive connection to the supercapacitor. Current sinks or sources from this pin to the capacitor depending on the mode of operation. CP, CN pins are connected to each side of the ceramic bucket capacitor used in the 2x charge pump mode. LEDA, LEDB are connected internally to the current sources and must be connected to the LED anodes. Each output is independently current regulated. These pins enter a high-impedance `zero' current state whenever the device is placed in shutdown mode or FLASH and TORCH are low. BAL is connected to the center-point between the two supercapacitor cells. An active circuit forces the BAL pin to remain at half of the voltage of the CAP output. RF is connected to a resistor (RF) to set the current in the LED channels in flash mode. The voltage on the pin is regulated to 0.6 V in flash mode (FLASH high). RT is connected to a resistor (RT) to set the current in the LED channels in torch mode. The voltage on the pin is regulated to 0.6 V in torch mode (TORCH high). RC is connected to a resistor (RC) to set the current limit on VIN when charging the supercapacitor. The voltage on the pin is regulated to 0.6 V in charge mode (CHRG high). CHRG is the charge mode enable pin. When high, the 1x/2x charge pump is enabled and allows to charge the supercapacitor and monitors its voltage. FLASH is the flash mode enable pin. When high, the LED current sources are enabled in flash mode. If FLASH is kept high for longer then 300 ms typical, the LED channels are automatically disabled. TORCH is the torch mode enable pin. When high, the LED current sources are enabled in torch mode. FLAG is an active-low open-drain output that notify to the microcontroller that the supercapacitor is fully charged by pulling the output low. When using the flag, this pin should be connected to a positive rail via an external pull-up resistor.
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CAT3224
Block Diagram
Figure 18. Functional Block Diagram
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CAT3224
Basic Operation The CAT3224 integrates in a single device two main functions: a dual cell supercapacitor charger and an LED driver. Two LED channels provide accurately regulated and matched current up to 2 A per channel. The charging mode is activated when the CHRG control input is pulled high and can remain active even during torch or flash mode. This allows continuous torch mode operation. The two modes, torch and flash, are activated using separate control inputs repectively TORCH and FLASH.
Charge Mode
current should be less than half the charging current. If the requested torch current is greater than half the input current, the LEDs will dim progressively according to the input current.
Flash Mode
When the FLASH input is set high, the driver is in flash mode and the LED channel current is set according to the external resistor connected between the RF pin and ground. The flash mode LED channel current can be calculated by the following equation (approximation).
I FLASH [ 900 I RF + 900 V RF + 900 RF 0.6 V RF
When the CHRG input is set high, the driver is in charge mode and the input supply current cannot exceed the current limit set by an external resistor connected between the RC pin and ground. The charging current limit is calculated by the following equation (approximation).
I IN [ 400 I RC + 400 V RC + 400 RC 0.6 V RC
Table 7 shows some standard resistor values for RF and the corresponding LED channel current.
Table 7. RSET Resistor Settings
LED Current per Channel [A] 1 1.5 2 RF [W] 549 360 261
If the CAP output voltage is lower than the charge threshold, the charging cycle starts. The driver charge pump initially starts in 1x mode and remains there as long as the supply voltage VIN is high enough to drive the CAP output voltage directly. In 1x mode, the output current charging the supercapacitor is approximately equal to the input current. The driver enters the 2x charge pump mode when the CAP pin voltage approaches VIN (VCAP VIN - 0.3 V). In 2x mode, the output current is approximately half of the input current. The charge cycle stops when either the CHRG input is pulled low or when the CAP output reaches the "CAP charge off voltage" threshold. As soon as the CAP output reaches the "CAP voltage FLAG pulled low" threshold, the FLAG output is pulled low. There is an hysteresis on the FLAG output which is illustrated in the timing diagram on Figure 2. The charge time is a function of the input voltage, input current setting, supercapacitor value, final CAP voltage. The RC pin has a current limit of 3.5 mA typical. If the RC pin is shorted to ground, the maximum charge current is 400 x 3.5 mA or 1.4 A.
Torch Mode
The maximum flash duration where the LED current is regulated depends on the initial CAP voltage, capacitor value, LED forward voltage and the LED flash current setting. The flash pulse duration can be calculated as follows.
T FLASH + C DV CAP I FLASH
where C is the total supercapacitor value, VCAP is the drop in the CAP voltage during the flash. See the Capacitor Selection section for more details. The RF pin has a current limit of 3.5 mA typical. If the RF pin is shorted to ground, the maximum flash LED current is 1000 x 3.5 mA or 3.5 A. During flash mode, the LEDs stay in regulation as long as their forward voltage does not exceed a maximum voltage calculated as follows:
V Fmax + V CAP * IOUT R CAP-ESR ) R LEDAB
The torch mode allows the LEDs to run for extended time duration but at a lower current than in the flash mode. When the TORCH input is set high, the driver is in torch mode and the LED channel current is set according to the external resistor connected between the RT pin and ground. The torch mode LED current per channel follows the equation:
I TORCH [ 120 I RT + 120 V RT + 120 RT 0.6 V RT
How long the LED current is regulated depends on the initial CAP voltage, capacitor value, the charge current, LED forward voltage and the LED torch current setting. In order to maintain regulation in 2x mode, the torch output
where IOUT is the CAP total output current, RCAP-ESR is the supercapacitor ESR (equivalent series resistance), and RLEDAB is the LEDA/B combined dropout resistance of the CAT3224. The transient waveform in Figure 19 shows the CAP output voltage during a 4 A flash pulse (2 A per LED channel) with CHRG low (not in charge mode). The initial drop on the CAP voltage (Vesr) is due to the supercapacitor ESR. In this example, it is calculated as follows.
Vesr + 2 I LED R CAP-ESR + 2x 2A 0.1 W + 0.4 V
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CAT3224
To support 4 A flash pulses, we recommend using the 0.55 F supercapacitor HS206F from CAP-XX with a voltage rating of 5.5 V and a low ESR of 85 m. In addition to the supercapacitor, a small 1 mF 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 1 mF ceramic capacitor between the BAL pin and GND. This will prevent any oscillation on the BAL pin and keep the quiescent current low.
Thermal Dissipation Figure 19. CAP Output Transient during 4 A Flash Flash Rate
Between two consecutive flash pulses, the supercapacitor needs some time to recharge. The supercapacitor time needed to fully recharge after a flash pulse is a function of the flash current and duration, and the charging current. Assuming the driver is in 2x mode, the charging time is calculated as follows.
T CHARGE + 2 I OUT IIN T FLASH
where IOUT is the total LED current, TFLASH is the flash duration and IIN is the input current. For example, a 60 ms 4 A flash pulse with a charge current of 300 mA corresponds to a recharge time:
T CHARGE + 2 Capacitor Selection 4A 0.3 A 0.06 s + 1.6 s
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 150C typical, the device goes into thermal shutdown mode and resumes normal operation as soon as the temperature drops by about 20C. To improve the thermal performance, the TQFN exposed pad should be connected to the PCB ground plane underneath.
Recommended Layout
The supercapacitor size depends on the flash requirement including flash duration, LED current and LED forward voltage. The minimum supercapacitor value is calculated as follows.
C+ I OUT T FLASH V CAP * I OUT R CAP-ESR ) R LEDAB * V F
where VCAP is the initial CAP voltage (5.2 V typical), and VF is the LED forward voltage. Any interconnection parasitic resistance is assumed negligible in the calculation. For example, for a 4 A flash with 0.1 s duration and 3.1 V LED VF, the minimum capacitor value is:
C+ 4A 0.1 s 5.2 V * 4 A 0.1 W ) 0.1 W * 3.1 V ^ 0.3 F
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. Therefore 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) should 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.
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CAT3224
PACKAGE DIMENSIONS
TQFN16, 3x3 CASE 510AD-01 ISSUE A
A
D
e
b L
E
E2
PIN#1 ID
PIN#1 INDEX AREA TOP VIEW
A1 SIDE VIEW
D2 BOTTOM VIEW
SYMBOL A A1 A3 b D D2 E E2 e L
MIN 0.70 0.00 0.18 2.90 1.40 2.90 1.40 0.30
NOM 0.75 0.02 0.20 REF 0.25 3.00 --- 3.00 --- 0.50 BSC 0.40
MAX 0.80 0.05 0.30 3.10 1.80 3.10 1.80 0.50 A1 FRONT VIEW A3
A
Notes: (1) All dimensions are in millimeters. (2) Complies with JEDEC MO-220.
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CAT3224
Example of Ordering Information (Note 4)
Prefix CAT Device # 3224 Suffix HV3 -G T2
Company ID (Optional)
Product Number 3224
Package HV3: TQFN
Lead Finish G: NiPdAu
Tape & Reel (Note 8) T: Tape & Reel 2: 2,000 / Reel
4. 5. 6. 7. 8.
The device used in the above example is a CAT3224HV3-GT2 (TQFN, NiPdAu, Tape & Reel, 2,000 / Reel). All packages are RoHS-compliant (Lead-free, Halogen-free). The standard lead finish is NiPdAu. For additional package and temperature options, please contact your nearest ON Semiconductor sales office. For information on tape and reel specifications, including part orientation and tape sizes, please refer to our Tape and Reel Packaging Specifications Brochure, BRD8011/D.
ON Semiconductor and are registered trademarks of Semiconductor Components Industries, LLC (SCILLC). SCILLC reserves the right to make changes without further notice to any products herein. SCILLC makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does SCILLC assume any liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation special, consequential or incidental damages. "Typical" parameters which may be provided in SCILLC data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. All operating parameters, including "Typicals" must be validated for each customer application by customer's technical experts. SCILLC does not convey any license under its patent rights nor the rights of others. SCILLC products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other applications intended to support or sustain life, or for any other application in which the failure of the SCILLC product could create a situation where personal injury or death may occur. Should Buyer purchase or use SCILLC products for any such unintended or unauthorized application, Buyer shall indemnify and hold SCILLC and its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that SCILLC was negligent regarding the design or manufacture of the part. SCILLC is an Equal Opportunity/Affirmative Action Employer. This literature is subject to all applicable copyright laws and is not for resale in any manner.
PUBLICATION ORDERING INFORMATION
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CAT3224/D

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