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AT1454/AT1454A/AT1454B
Preliminary Product Information Photoflash Capacitor Charger for DSC Feature * 2.5V to 5.5V Supply Voltage Operating * * * * * * * * * * *
Range. Low Current Consumption:1mA in operation. Adjustable Output Voltage. Adjustable Switch On-Time. Charge Complete Indicator. Built-in IGBT Driver. Soft-Start Circuitry. Thermal Protection Charges Any Size Photoflash Capacitor. AT1454 with Auto-Refresh Function. AT1454A/B without Auto-Refresh Function. Small 10-lead MSOP Package.
Description
The AT1454 series is a charger IC for Photoflash capacitor with soft-start function, an IGBT driver for igniting flash tube, adjustable output voltage and adjustable switch on-time to perform energy transition on each charge cycle. The output voltage can be adjusted by simply changing the turn ratio of transformer. AT1454B is sensed by voltage divider connecting to the anode of the rectifying diode. The voltage sensing path is cut off when charging function to be completed to maintain minimum output voltage decay. The device allows user to control automatic refresh rate on Charge pin. While the Ready pin signals that the capacitor is fully charged. AT1454/AT1454A/AT1454B MSOP-10 package. is available in
Application * Digital / Film Camera Flash * PDA / Cell Phone Flash.
Block Diagram
Aimtron reserves the right without notice to change this circuitry and specifications.
7F, No.9,PARK AVENUE. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 3/24/2006 REV:1.2 Email: service@aimtron.com.tw 1
AT1454/AT1454A/AT1454B
Preliminary Product Information Photoflash Capacitor Charger for DSC Pin Configuration
1 0
9
8
7
6
1454
1 2 3 4 5
Ordering Information
Part number AT1454M_GRE AT1454AM_GRE AT1454BM_GRE Package MSOP-10 , Green MSOP-10 , Green MSOP-10 , Green Marking AT1454, Date code with one bottom line AT1454A, Date code with one bottom line AT1454B, Date code with one bottom line
*For more marking information, contact our sales representative directly
Pin Description
Pin N0. Symbol 1 CHARGE 2 FB 3 TRIGGER 4 5 6 7 8 9 10 ISEC GND LX DRIVER VCC READY Rsense I/O I I I I P I O P O I Description Charge enable input Comparator input IGBT Trigger signal input. Detecting transformer secondary current. Take care to use the correct phasing of the transformer. Ground Power MOSFET N-channel Drain. Connect Primary transformer. Take care to use the correct phasing of the transformer. IGBT Driver output. Power supply. Charge ready open drain output. A resistor from Rsense to VCC or VBAT sets the constant On-time.
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AT1454/AT1454A/AT1454B
Preliminary Product Information Photoflash Capacitor Charger for DSC Absolute Maximum Ratings*1
Parameter VCC , TRIGGER , DRIVER , CHARGE , FB and READY voltage LX voltage SEC Current Continuous power dissipation (MSOP-10,Ta=+25 C) Junction Temperature Lead Temperature (Soldering 10 sec) HBM MM Storage Temperature ESD Susceptibility*2
O
Rated Value -0.3 to +6.0 +30 300 555 125 260 -40~125 2 200
Unit V V mA mW KV V
1. Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. 2. Device are ESD sensitive. Handling precaution recommended. The Human Body model is a 100pF capacitor discharged through a 1.5K resistor into each pin.
Recommended Operation Conditions
Parameter Power supply voltage Operating temperature LX voltage Symbol VCC Top VLX Min. 2.5 -30 VCC Values Typ. +25 Max. +5.5 +85 28 Unit V V
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AT1454/AT1454A/AT1454B
Preliminary Product Information Photoflash Capacitor Charger for DSC Electrical Characteristics
(VCC=3.3V, Ta=+25, unless otherwise noted)
Parameter Input operating voltage Input under-voltage threshold VCC UVLO hysteresis Feedback voltage Shutdown current Quiescent Current Primary side current limit Secondary side transit current LX Switch On-Resistance LX Leakage Current IGBT Driver Rising time IGBT Driver Falling time IGBT Trigger signal high IGBT Trigger signal low Charge input voltage high Charge input voltage low Charge pin Bias current Ready output signal high Ready output signal low Thermal Shutdown
Symbol VCC VUVLO VFB IOFF Icc ILX(MAX) Isec
Test Condition VCC falling Ta=+25 CHARGE pin=GND No Switching , FB=1.2V
Min. 2.5 1.08
0.45Vc c
Typ. Max. Units 2.1 100 1.10 0.01 40 2.5 5 0.17 0.01 55 90 55 90 3 3.27 1.0 140 5.5 1.12 1 60 6
0.3Vcc
V V mV V A A A mA A ns ns ns ns V V V V A V mV
RLX(ON) ILX=2A ILC tr tf VLX=28V VCC=3.3V, CL=3900pF VCC=3.3V, CL=8200pF VCC=3.3V, CL=3900pF VCC=3.3V, CL=8200pF
VON VOFF VCHARGE =3.3V 100k from Vcc to Ready pin 33A into Ready pin 0.1V hysteresis 0.9
0.8 0
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AT1454/AT1454A/AT1454B
Preliminary Product Information Photoflash Capacitor Charger for DSC Timing Chart
Vcc
Trige
READY
VOUT
CHARGE
Charge On Timing Power OFF Timing
Shutdown
Charging
Auto charge to Refresh
Storbe
AT1454 Auto-Refresh Mode
Vcc
Trige
READY
VOUT
CHARGE
Charge On Timing
Power OFF Timing
Shutdown
Charging
Toggling CHARGE to Refresh
Storbe
1.uP Detected READY pin Low ->High(Charge Complete) -->allow enter refresh mode or strobe tube 2.Use uP to delay Photoflash Capacitor self-discharge time Ts 3.Toggling CHARGE pin high->low->high, force the IC into refresh charging mode.
AT1454A/B Charge Toggle-Refresh (Soft-ware control)Mode
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AT1454/AT1454A/AT1454B
Preliminary Product Information Photoflash Capacitor Charger for DSC Typical Operating Characteristics
VLX & Primary Current Time(1us/Div) [CH2:VLX; CH4:IPRI]
Vout=100V
VLX(5V/Div)
IPRI(1A/Div)
Vout=100
VLX & Primary Current Time(1us/Div) [CH2:VLX; CH4:IPRI]
Vout=300V
VLX(10V/Div)
IPRI(1A/Div)
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AT1454/AT1454A/AT1454B
Preliminary Product Information Photoflash Capacitor Charger for DSC
VLX & Secondary Current Time(1us/Div) [CH2:VLX; CH4:ISEC]
Vout=100V
VLX(5V/Div)
ISEC(50mA/Div
Charging waveform without auto-refresh function , Time(1 s/Div) VCC=3.3V, VBAT=4.2V, C=120uF
CH1:READY CH2:CHARGE CH3:Output Voltage
CH4:Input Current
7F, No.9,PARK AVENUE. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 3/24/2006 REV:1.2 Email: service@aimtron.com.tw 7
AT1454/AT1454A/AT1454B
Preliminary Product Information Photoflash Capacitor Charger for DSC
Charging waveform with auto-refresh function , Time(1 s/Div) VCC=3.3V, VBAT=3.0V, C=47uF
CH1:READY CH2:CHARGE
CH3:Output Voltage
CH4:Input Current
7F, No.9,PARK AVENUE. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 3/24/2006 REV:1.2 Email: service@aimtron.com.tw 8
AT1454/AT1454A/AT1454B
Preliminary Product Information Photoflash Capacitor Charger for DSC Application Circuit
7F, No.9,PARK AVENUE. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 3/24/2006 REV:1.2 Email: service@aimtron.com.tw 9
AT1454/AT1454A/AT1454B
Preliminary Product Information Photoflash Capacitor Charger for DSC
7F, No.9,PARK AVENUE. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 3/24/2006 REV:1.2 Email: service@aimtron.com.tw 10
AT1454/AT1454A/AT1454B
Preliminary Product Information Photoflash Capacitor Charger for DSC
7F, No.9,PARK AVENUE. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 3/24/2006 REV:1.2 Email: service@aimtron.com.tw 11
AT1454/AT1454A/AT1454B
Preliminary Product Information Photoflash Capacitor Charger for DSC Application Information AT1454 series is designed to precise control of switching current to charge photoflash capacitors quickly and efficiently. When the Charge pin is first driven high, a one shot set SR latches in the correct state. The built-in power MOSFET turns on and primary current ramps up linearly according to VBAT and primary inductance. Comparator monitors the switch On-time and when the switch on-time reaches limit value, MOSFET is turned off. During this phase, stored energy of primary transformer is delivered to the photoflash capacitor via the secondary and diode. The secondary current is decreased linearly at a rate determined by the secondary inductance. The secondary current is monitored by the Isec pin. When the secondary current drops below 10mA, the fires a one shot will turn on MOSFET. The charging cycle repeats to deliver power to the output. AT1454 series can adjust external resistance RSENSE to set N-MOS switch on-time, but switch on-time value must match with electrical characteristic of transformer. It is usually equal to or less than saturation current of transformer otherwise transformer will be saturated. Therefore, efficiency will be reduced. The output voltage is detected by a voltage divider connecting to output capacitor. When the output voltage reaches the desired voltage set by resistive voltage-divider, comparator output goes high which resets the master latch and disable the charging block. The N-channel MOSFET is turned off pulling the Ready pin high, indicating that the part has finished charging. Power delivery can be restarted automatically when feedback voltage is less than 90% of reference voltage. Power delivery can only be restarted by toggling the Charge pin. The Charge pin gives full control of the part to the user. The IGBT buffer will provide a sufficient current to drive IGBT to ignite flash tube.
Transformer Design The Fly-back transformer is a key element for AT1454 series. It must be designed carefully and checked that it does not cause excessive current or voltage on any pin of the part. The first transformer parameter that needs to be set is the turns ratio N, should be high enough so that the absolute maximum voltage rating for the NMOS drain to source voltage is not exceeded. Choose the minimum turns ratio according to following formula:
N MIN VOUT V DS ( MAX ) - V BAT
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AT1454/AT1454A/AT1454B
Preliminary Product Information Photoflash Capacitor Charger for DSC Vout: Target Output Voltage VDS(MAX):Maximum drain to source voltage of NMOS. Adjustable Output Voltage The AT1454/1454A/B senses output voltage by a voltage divider connecting to output terminal. R7 to (R8+R9) ratio determines the output voltage as shown in the application circuit Figure 1. The feedback reference voltage is 1.1V. Calculate the remaining resistors with following equations:
VOUT = V FB x (1 + R8 + R9 ) R7
R8and R9 must be greater than 0805 size resistor for enduring secondary HV. Rectifying Diode The rectifying diode should be low capacitance type with sufficient reverse recovery-voltage and forward current ratings. The peak reverse recovery-voltage that diode is approximately: VPK-R VOUT + (N x VCC) The peak current of the diode is simply: IPK-SEC= IPK-PRI / N
Primary Inductance A fly-back transformer needs to store substantial amounts of energy in the core during each switching cycle. The transformer will generally require an air gap. The use of an air gap in the core makes the energy storage. While the power switch is off, energy transferred to the output capacitor is proportional to the primary inductance for a constant primary current. The primary inductance needs to be equal or larger than a certain minimum value to ensure that AT1454 series has adequate time to respond to the fly-back waveform. The switch off time should be 500ns or larger for the AT1454 series. The minimum inductance can be calculated with the following formula: 500 x 10 -9 x VOUT LPRI N x I PK - PRI Vout: Target Output Voltage N: Transformer Turns Ratio IPK-PRI: Primary Peak Current
7F, No.9,PARK AVENUE. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 3/24/2006 REV:1.2 Email: service@aimtron.com.tw 13
AT1454/AT1454A/AT1454B
Preliminary Product Information Photoflash Capacitor Charger for DSC Leakage Inductance and Parasitic Capacitance The leakage inductance on the primary of the transformer results in the first spike voltage when NMOS turns off. The spike voltage is proportional to the leakage inductance. The spike voltage must not exceed the dynamic rating of the NMOS drain to source voltage. It is important not to minimize the leakage inductance to a very low level. Although this would result in a very low leakage spike, the parasitic capacitance of the transformer will be high between windings. This will result in the initial spike of current in the primary becoming excessively high while the NMOS turns on. Therefore, trade off is necessary between leakage inductance and parasitic capacitance.
Spike Voltage @SwitchingTime(1us/Div) VLX(5V/Div) , IPRI(1A/Div) Swing Current @SwitchingTime(1us/Div) VLX(10V/Div) , IPRI(1A/Div)
Spike Voltage CH1
Swing Current CH2
CH1:VLX; CH2:Input Current
Transformer Secondary Capacitance The total capacitance on the secondary of the transformer will severely affect the efficiency of the circuit. Any secondary capacitance is multiplied by N2 when reflected to the primary. Since this capacitance forms a resonant circuit with the primary leakage inductance of the transformer. As such, both the primary leakage inductance and secondary side capacitance should be minimized.
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AT1454/AT1454A/AT1454B
Preliminary Product Information Photoflash Capacitor Charger for DSC Adjustable Input Current The AT1454/1454A/B can adjust N-MOS switch on-time by a resistor connecting to Rsense pin. This resistor determines the primary peak current and on-time of primary N-MOS as the following equation:
I PK - PRI = TON = V BAT x 2 x 10 -6 25 K , V Rsense = V BAT (or , VCC ) x V Rsense x L PRI R4 + 25 K
I PK - PRI x L PRI V BAT
where LPRI: primary inductance (H) IPK-PRI: peak primary current (A) R4: It is recommended several K grade If setting constant on-time by a resistor R10 is connected to VCC, then R4 resistor need to remove from application circuitry. In this case, on-time is a constant. At another topology, if R4 connect to VBAT to set constant on-time, then R10 need to remove from application circuitry. However, on-time can change dependent on VBAT because battery voltage level is different from full energy to low power. External capacitor Css is connected to VCC and Rsense to perform soft-start function to reduce inrush current on VBAT input current and avoid the internal switching noise.
L1 33uH /Option C1 22u/6V3 T1 ST-982610A 1:25 10uH/6.1mH
VBAT VCC R10
R4
Css 0.1uF VCC Rsense LX
Isec AT1454/AT1454A/AT1454B
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AT1454/AT1454A/AT1454B
Preliminary Product Information Photoflash Capacitor Charger for DSC Auto-Refresh AT1454 supports auto-refresh function required in some DCS application. When the output capacitor is charged complete, the READY pin will goes high and Vout will decrease slightly due to leakage current. The refresh block trip point is VFBx90%. While the Vout is decreased to the refresh trip point, it enables the charge block, disable the refresh block and pull low the READY pin. This cycle of recharge operation will repeat again until charge pin is pulled low. Thermal-Overload Protection Thermal-overload protection limits total power dissipation in the AT1454 series. When the junction temperature exceeds Tj=140 , a thermal sensor activates the thermal protection, which shuts down the IC, allowing the IC to cool. Once the device cools down by 15 , IC will automatically recover normal operation. For continuous operation , do not exceed the absolute maximum junction-temperature rating of Tj=130 . Prevent the Leakage of READY pin
VCC
CHARGE
READY
READY
If pull-high resistor of READY signal connect to Charge pin, then it can reduce power consumption on pull-high resistor of READY during charge pin goes low.
Board Layout The high voltage operation of the AT1454/AT1454A/AT1454B demands careful attention to board layout. You will not get advertised performance with careless layout. Keep the area for the high voltage end of the secondary as small as possible. Also note the larger than minimum spacing for all high voltage nodes in order to meet breakdown voltage requirements for the circuit board. Remember that lethal voltages are present in this circuit. Use caution when working with the circuit.
7F, No.9,PARK AVENUE. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 3/24/2006 REV:1.2 Email: service@aimtron.com.tw 16
AT1454/AT1454A/AT1454B
Preliminary Product Information Photoflash Capacitor Charger for DSC Outline 10-pin MSOP
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AT1454/AT1454A/AT1454B
Preliminary Product Information Photoflash Capacitor Charger for DSC Reflow Profiles
Profile Feature
Average ramp-up rate (TL to TP) Preheat -Temperature Min(Tsmin) -Temperature Max (Tsmax) -Time (min to max)(ts) Tsmax to TL -Ramp-up Rate Time maintained above: -Temperature (TL) -Time (tL) Peak Temperature(TP) Time within 5C of actual Peak Temperature (tP) Ramp-down Rate Time 25C to Peak Temperature
Sn-Pb Eutectic Assembly Large Body Small Body Pkg. thickness Pkg. thickness <2.5mm or Pkg. 2.5mm or Pkg. 3 volume <350mm3 volume 350mm 3C/second max.
Pb-Free Assembly Large Body Small Body Pkg. thickness Pkg. thickness 2.5mm or Pkg. 2.5mm or Pkg. 3 volume 350mm volume 350mm3 3C/second max.
100C 150C 60-120 seconds
150C 200C 60-180 seconds 3C/second max.
183C 60-150 seconds 225+0/-5C 10-30 seconds 240+0/-5C 10-30 seconds
217C 60-150 seconds 245+0/-5C 10-30 seconds 250+0/-5C 20-40 seconds
6C/second max. 6 minutes max.
3C/second max. 8 minutes max.
*All temperatures refer to topside of the package, measured on the package body surface.
7F, No.9,PARK AVENUE. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 Fax: 886-3-563-0879 WWW: http://www.aimtron.com.tw 3/24/2006 REV:1.2 Email: service@aimtron.com.tw 18

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