A8731 Mobile Phone Xenon Photoflash Capacitor Charger With IGBT Driver Features and Benefits Description ▪ Low quiescent current draw (0.01 μA in shutdown mode) ▪ Primary-side output voltage sensing; no resistor divider required ▪ User-adjustable current limit from 0.4 to 1.2 A ▪ 1.1 V logic (VHI(min)) compatibility ▪ Integrated IGBT driver with internal gate resistors ▪ Flexible dual trigger inputs for IGBT driver ▪ Optimized for mobile phone, 1-cell Li+ battery applications ▪ No primary-side Schottky diode needed ▪ Zero-voltage switching for lower loss ▪ >75% efficiency ▪ Charge complete indication ▪ Integrated 40 V DMOS switch The Allegro® A8731 Xenon photoflash charger IC is designed to meet the needs of ultra-low power, small form factor cameras, particularly camera-phones. The charge time is adjustable by setting the charge current limit from 0.4 to 1.2 A maximum. By using primary-side voltage sensing, the need for a secondary-side resistive voltage divider is eliminated. This has the additional benefit of reducing leakage currents on the secondary side of the transformer. To extend battery life, the A8731 features very low supply current draw—typically 0.01 μA in shutdown mode and 10 μA in standby mode. The A8731 has a flash dual trigger IGBT driver. The IGBT driver also has internal gate resistors for minimum external component count. The charge and trigger voltage logic thresholds are set at 1.1 VHI (min) to support applications implementing low voltage control logic. The A8731 is available in a 10-contact 3 mm × 3 mm DFN package with a 0.75 nominal overall package height, and an exposed pad for enhanced thermal performance. Applications ▪ Mobile phone flash ▪ Digital and film camera flash Package: 10-contact DFN with exposed thermal pad (package EJ) Approximate Scale 1:1 Typical Applications 1 : 10 1 : 10 C2 Battery Input + 2.3 to 5.5 V C1 C2 COUT 100 μF 315 V VIN Battery Input + 2.3 to 5.5 V C1 VOUT Detect VOUT Detect SW ISET RSET SW ISET Control Block COUT 100 μF 315 V VIN ISW sense RSET Control Block ISW sense VPULLUP VPULLUP 100 kΩ DONE CHARGE DONE DONE VIN VIN TRIGGER1 IGBT Driver IGBT Gate TRIGGER1 IGBT Driver IGBT Gate GATE GATE TRIGGER2 TRIGGER2 GND Figure 1. Typical application with separate trigger inputs. A8731-DS, Rev. 1 100 kΩ DONE CHARGE GND Figure 2. Typical application with single trigger input. Mobile Phone Xenon Photoflash Capacitor Charger With IGBT Driver A8731 Selection Guide Part Number A8731EEJTR-T Package Packing 10-contact DFN Tape and reel, 1500 pieces per reel *Contact Allegro for additional ordering information. Absolute Maximum Ratings Characteristic Symbol Notes Rating Units –0.3 to 40 V –0.3 to 6.0 V –0.6 to VIN + 0.3 V V –0.3 to VIN + 0.3 V V DC voltage. SW Pin VSW VIN Pin VIN (VSW is self-clamped by internal active clamp and is allowed to exceed 40 V during flyback spike durations. Maximum repetitive energy during flyback spike: 0.5 μJ at frequency ≤ 400 kHz.) Care should be taken to limit the current when –0.6 V is applied to these pins. ¯¯N¯¯E¯ Pins CHARGE, TRIGGERx, ¯D¯¯O Remaining Pins Operating Ambient Temperature Maximum Junction Storage Temperature TA –40 to 85 ºC TJ(max) Range E 150 ºC Tstg –55 to 150 ºC Thermal Characteristics Characteristic Package Thermal Resistance Symbol RθJA Value Units On 2-layer PCB with 0.88 in.2 area of 2 oz. copper each side, based on JEDEC standard Test Conditions* 65 ºC/W On 4-layer PCB based on JEDEC standard 45 ºC/W *Additional thermal information available on Allegro website. Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com 2 Mobile Phone Xenon Photoflash Capacitor Charger With IGBT Driver A8731 Functional Block Diagram VIN SW VSW – VBAT DCM Detector ISET toff(max) ISET Buffer VDSref Control Logic DMOS 18 μs HmL Triggered Timer OCP S Q R Q ton(max) 18 μs Enable S Q R Q DONE One Shot CHARGE VIN IGBT Driver GATE TRIGGER1 TRIGGER2 GND Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com 3 Mobile Phone Xenon Photoflash Capacitor Charger With IGBT Driver A8731 Pin-out Diagram ISET 1 GATE 2 VIN 3 GND CHARGE 10 NC 9 DONE 8 TRIGGER1 4 7 SW 5 6 TRIGGER2 PAD (Contacts Down View) Terminal List Table Number Name 1 ISET 2 GATE 3 VIN Function Sets the maximum switch current; connect an external resistor to GND to set the desired peak current IGBT gate drive – sink/source Input voltage; connect to a 2.3 to 5.5 V battery supply 4 GND 5 CHARGE Ground connection 6 TRIGGER2 7 SW 8 TRIGGER1 9 ¯D¯¯O ¯¯N¯¯E¯ 10 NC No connection , electrically floating pin – PAD Exposed pad for enhanced thermal dissipation; connect to ground plane Pull high to initiate charging; pull low to enter low-power standby mode IGBT input trigger 2 Drain connection of internal power MOSFET switch; connect to transformer primary winding IGBT input trigger 1 Pulls low when output reaches target value and CHARGE pin is high; goes high during charging or whenever CHARGE pin is low Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com 4 A8731 Mobile Phone Xenon Photoflash Capacitor Charger With IGBT Driver ELECTRICAL CHARACTERISTICS typical values valid at VIN = 3.6 V, RSET = 33 kΩ, ISWlim = 1.0 A, and TA=25°C, unless otherwise noted Characteristics VIN Voltage Range UVLO Enable Threshold UVLO Hysteresis VIN Supply Current Symbol VIN VINUV VINUVhys IIN Test Conditions VIN rising Shutdown (CHARGE = 0 V, TRIGGER1 and TRIGGER2 = 0 V) Charging complete Charging (CHARGE = VIN, TRIGGER1 and TRIGGER2 = 0 V) Min. 2.3 – – Typ. – 2.05 150 Max. 5.5 2.2 – Unit V V mV – 0.01 0.5 μA – 10 50 μA – 2 – mA 1.08 – – – – – – 1.2 0.4 28 1.2 1000 0.25 – 1.32 – – – – – 2 A A kA/A V Ω Ω μA – – 0.5 μA – 1.1 – – – – – 36 – – 100 20 18 18 – – 0.4 – – – – μA V V kΩ us μs μs Current Limits Switch Current Limit1 SW / ISET Current Ratio ISET Pin Voltage While Charging ISET Pin Internal Resistance Switch On-Resistance Switch Leakage Current2 ISWlimMAX ISWlimMIN ISW/ISET VSET RSET(INT) RSWDS(on) ISWlk CHARGE Input Current ICHARGE CHARGE Input Voltage2 VCHARGE CHARGE Pull-Down Resistor Value CHARGE ON/OFF Delay Maximum Switch-Off Timeout Maximum Switch-On Timeout RCHPD tCH toffMAX tonMAX ¯D¯¯O ¯¯N¯¯E¯ Output Leakage Current2 IDONElk ¯D¯¯O ¯¯N¯¯E¯ Output Low Voltage2 VDONEL RSET = 26.7 kΩ RSET = 85 kΩ CHARGE = high CHARGE = high VIN = 3.6 V, ID = 800 mA, TA = 25°C VSW = VIN(max), over temperature range Combined VIN and SW leakage current at TA=25°C VIN= 5.5 V in Shutdown VCHARGE = VIN High, over input supply range Low, over input supply range Time between CHARGE = 1 and charging enabled – – 1 μA – 31 – – – 31.5 200 20 100 32 400 – mV V mV V/μs VTRIG(H) Input = logic high, over input supply range 1.1 – VTRIG(L) Input = logic low, over input supply range – – TRIGGER, TRIGGER2 Pull-Down Resistor RTRIGPD – 100 GATE Resistance to VIN RSrcDS(on) VIN = 3.6 V, VGATE =1.8 V – 23 GATE Resistance to GND RSnkDS(on) VIN = 3.6 V, VGATE = 1.8 V – 30 Propagation Delay (Rising) tDr – 110 Propagation Delay (Falling) tDf – 140 Measurement taken at pin, CL= 6500 pF, VIN = 3.6 V Output Rise Time tr – 290 Output Fall Time tf – 360 1Current limit guaranteed by design and correlation to static test. Refer to application section for peak current in actual circuits. 2Specifications over the range T = –40°C to 85°C; guaranteed by design and characterization. A – 0.4 – – – – – – – V V kΩ Ω Ω ns ns ns ns Output Comparator Trip Voltage2 Output Comparator Overdrive dV/dt Threshold of ZVS Comparator IGBT Driver TRIGGER, TRIGGER2 Input Voltage2 VOUTTRIP VOUTOV dV/dt ¯¯N¯¯E¯ pin 32 μA into ¯D¯¯O Measured as VSW – VIN Pulse width = 200 ns (90% to 90%) Measured at SW pin Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com 5 A8731 Mobile Phone Xenon Photoflash Capacitor Charger With IGBT Driver IGBT Drive Timing Definition TRIGGER 50% tDr 50% tr tDf 90% GATE 10% tf 90% 10% IGBT Drive Timing Characteristic Performance CGATE = 6200 pF. VIN = 3.6 V, Time = 200 ns/div; CH1 = TRIGGER input, 2 V/div, CH2 = Gate driver output, 1 V/div Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com 6 Mobile Phone Xenon Photoflash Capacitor Charger With IGBT Driver A8731 A8731 Operation Timing Diagram VIN UVLO CHARGE SW Target VOUT VOUT DONE T2 T1 T3 TRIGGER1 and TRIGGER2 IGBTDRV A B C D E F Explanation of Events A: Start charging by pulling CHARGE to high, provided that VIN is above UVLO level. B: Charging stops when VOUT reaches the target voltage. C: Start a new charging process with a low-to-high transition at the CHARGE pin. D: Pull CHARGE to low to put the controller in low-power standby mode. E: Charging does not start, because VIN is below UVLO level when CHARGE goes high. F: After VIN goes above UVLO , another low-to-high transition at the CHARGE pin is required to start the charging. T1, T2, T3 (Trigger instances): IGBT driver output pulled high whenever both TRIGGER pins are logic high. It is recommended to avoid applying any trigger pulses during charging. Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com 7 Mobile Phone Xenon Photoflash Capacitor Charger With IGBT Driver A8731 Performance Characteristics Charging Time at Various Peak Current Levels Common Parameters Symbol Parameter Units/Division C1 VOUT 50 V C2 VBAT 1V C3 IIN 100 mA t time 200 ms Conditions Parameter Value VBATT 3.6 V COUT 20 μF Conditions Parameter RSET ISWlim Value 26.7 kΩ ≈1.2 A VOUT VBAT C1 C2 IIN C1 C2 C3 C3 t VOUT C1 VBAT Conditions Parameter RSET ISWlim Value 33.2 kΩ ≈1.0 A C2 IIN C1 C2 C3 C3 t VOUT C1 VBAT Conditions Parameter RSET ISWlim Value 39 kΩ ≈0.9 A C2 IIN C1 C2 C3 C3 t Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com 8 Mobile Phone Xenon Photoflash Capacitor Charger With IGBT Driver A8731 Efficiency versus Battery Voltage Charge Time versus Battery Voltage Transformer Lp= 8 μH, N = 10.2; COUT= 20 μF / 330 V UCC; TA=25° Transformer Lp= 8 μH, N = 10.2; COUT= 20 μF / 330 V UCC; TA=25° 71 3.5 2.0 45 ≈ 0.8 67 39 ≈ 0.9 66 33.2 ≈ 1.0 65 26.7 ≈ 1.2 69 68 1.5 1.0 0.5 64 62 RSET (kΩ) 55 IP (A) ≈ 0.65 61 45 ≈ 0.8 60 39 ≈ 0.9 59 33.2 ≈ 1.0 58 26.7 ≈ 1.2 63 57 56 55 0 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 2.0 6.0 2.5 3.0 3.5 VBAT (V) COUT= 20 μF. For larger or smaller capacitances, charging time scales proportionally. 4.0 VBAT (V) 4.5 5.0 5.5 6.0 Special low-profile transformer with relatively low inductance (Lp= 8 μH) and high winding resistance (Rp = 0.37 Ω). Higher efficiency can be achieved by using transformers with higher Lp, which reduces switching frequency and therefore switching loses, and lower resistance, which reduces conduction losses. Average Input Current versus Battery Voltage XFM Lp= 8 μH, N = 10.2, COUT= 20 μF 330 V UCC, TA=25° 0.55 0.50 0.45 0.40 IIN (A) Time (s) 2.5 IP (A) ≈ 0.65 Efficiency (%) 3.0 70 RSET (kΩ) 55 0.35 0.30 RSET (kΩ) 26.7 IP (A) ≈ 1.2 33.2 ≈ 1.0 39 ≈ 0.9 45 ≈ 0.8 55 ≈ 0.65 0.25 0.20 0.15 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 VBAT (V) An increase in ISWlim with respect to VBAT actually keeps the average input current roughly constant throughout the battery voltage range. Normally, if ISWlim is kept constant, the average current will drop as VBAT goes higher. Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com 9 Mobile Phone Xenon Photoflash Capacitor Charger With IGBT Driver A8731 Application Information transformer primary inductance, Lp. If necessary, the The CHARGE pin enables the part and starts charging. following expressions can be used to determine ISWlim ¯ open-drain indicator is pulled low when The ¯¯¯ D¯ ¯O¯¯¯N¯¯E more accurately: CHARGE is high and target output voltage is reached. Pulling the CHARGE pin low stops charging and ISET = VSET / (RSET + RSET(INT) – K × RGND(INT) ), (2) forces the chip into low-power standby mode. where: Selection of Switching Current Limit RSET(INT) is the internal resistance of the ISET pin The A8731 features continuously adjustable peak (1 kΩ typical), switching current between 0.4 and 1.2A. This is done by selecting the value of an external resistor RSET, RGND(INT) is the internal resistance of the bonding connected from the ISET pin to GND, which deterwire for the GND pin (27 mΩ typical), and mines the ISET bias current, and therefore the switching current limit, ISWlim. K = (K′ + VIN × K″), with K′ = 24350 and To the first order approximation, ISWlim is related to K″ ≈ 1040 at TA = 25°C. Then, ISET and RSET according to the following equations: ISWlim = ISET × K + VBAT / LP × tD , (3) (1) ISWlim = ISET × K = VSET / RSET × K , where tD is the delay in SW turn-off (0.1 μs typical). where K = 28000 when battery voltage is 3.6 V. Figure 3 can be used to determine the relationship In real applications, the actual switching current limit is affected by input battery voltage, and also the between RSET and ISWlim at various battery voltages. General Operation Overview 1.3 1.2 1.1 VIN = 5.5 V VIN = 4.5 V ISWlim (A) 1.0 VIN = 3.6 V VIN = 3.0 V 0.9 VIN = 2.3 V 0.8 0.7 0.6 0.5 0.4 25 30 35 40 45 50 55 60 65 70 75 80 85 90 RSET (kΩ) Figure 3. Peak Current Limit versus ISET Resistance. VIN = VBAT, transformer LP = 8 μH, TA = 25°C. 10 Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com Mobile Phone Xenon Photoflash Capacitor Charger With IGBT Driver A8731 Smart Current Limit (Optional) With the help of some simple external logic, the user can change the charging current according to the battery voltage. For example, assume that ISET is normally 36 μA (for ISWlim = 1.0 A). Referring to figure 4, when the battery voltage drops below 2.5 V, the signal at BL (battery-low) goes high. The resistor RBL, connecting BL to the ISET pin, then injects 10 μA into RSET. This effectively reduces ISET current to 26 μA (for ISWLIM = 0.73 A). Timer Mode and Fast Charging Mode The A8731 achieves fast charging times and high efficiency by operating in discontinuous conduction mode (DCM) through most of the charging process The BL RBL ISET RSET relationship of Timer Mode and Fast Charging Mode is shown in figure 5. The IC operates in Timer Mode when beginning to charge a completely discharged photoflash capacitor, usually when the output voltage, VOUT, is less than approximately 15 to 20 V. Timer Mode is a fixed period, 18 μs, off-time control. One advantage of having Timer Mode is that it limits the initial battery current surge and thus acts as a “soft-start.” A timeexpanded view of a Timer Mode interval is shown in figure 6. As soon as a sufficient voltage has built up at the output capacitor, the IC enters Fast-Charging Mode. In this mode, the next switching cycle starts after the secondary side current has stopped flowing, and the switch voltage has dropped to a minimum value. A proprietary circuit is used to allow minimum-voltage switching, even if the SW pin voltage does not drop to 0 V. This enables Fast-Charging Mode to start earlier Figure 4. Smart Current Limit reference circuit VOUT Timer Mode Fast Charging Mode VBAT VSW VBAT IIN VOUT ISW Figure 5. Timer Mode and Fast Charging Mode. t =200 ms/div, VOUT =50 V/div, VBAT =1 V/div., IIN =100 mA/div., VBAT =3.6 V, COUT =20 μF/330 V, RSET=46 kΩ (ISWlim≈0.75 A). Figure 6. Timer Mode expanded view. VOUT ≤ 14 V, t = 2 μs / div., VBAT = 3.6 V, RSET = 33.2 kΩ. 11 Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com A8731 Mobile Phone Xenon Photoflash Capacitor Charger With IGBT Driver than previously possible, thereby reducing the overall charging time. Minimum-voltage switching is shown in figure 7. During Fast-Charging Mode, when VOUT is high enough (over 50 V), true zero-voltage switching (ZVS) is achieved. This further improves efficiency as well as reduces switching noise. A ZVS interval is shown in figure 8. IGBT Gate Driver Inputs The TRIGGER1 and TRIGGER2 pins are ANDed together inside the IC to control the IGBT gate driver. If only one trigger signal is needed, tie both trigger pins together and use as a single input. Ambient Light Sensing Ambient Light Sensing (ALS) can be easily implemented for the A8731 using the TRIGGER2 pin plus three external components. This configuration is shown in figure 9. The phototransistor current is proportional to the intensity of the light that it receives. When there is sufficient ambient light (for example, during daylight outdoor photographing), a current of about 30 μA can flow through the phototransistor. This forces the voltage at TRIGGER2 pin to fall to 0.8 V or lower, so it prohibits TRIGGER1 from firing the flash. The exact threshold of ambient light required to prohibit flash firing can be adjusted by RTGR1. The smaller this resistance, the brighter the ambient light must be to prohibit flash firing. When ambient conditions are dark, the current flowing through the phototransistor is in less than 1 μA. Because the TRIGGER2 pin is biased at 1.4 V or higher, TRIGGER1 is allowed to activate the IGBT gate driver (and thereby fire the flash). The capacitor CTGR1 and resistor RTGR1 form an integrator for light exposure. When the flash fires, bright light bounces back from subject and enters the phototransistor. In example A in figure 10, the flash terminates after just 30 μs, without fully discharging the photoflash capacitor. VOUT Minimum Voltage Switching VSW VSW VBAT VOUT ISW Figure 7. Minimum voltage switching. VOUT ≥ 15 V; t =1 μs/div., VBAT = 3.6 V, RSET = 33.2 kΩ. Zero Voltage Switching VSW VBAT VBAT ISW VOUT ISW Figure 8. Zero voltage switching. VOUT = 120 V. t = 0.2 μs/div., VBAT = 3.6 V, RSET = 33.2 kΩ. 12 Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com Mobile Phone Xenon Photoflash Capacitor Charger With IGBT Driver A8731 Battery Input 2.5 to 5.5 V If the subject is far away, the reflected light intensity is lower, so the phototransistor current is also lower. In example B, the flash stays on for longer time (60 μs) and discharges more energy from the photoflash capacitor. Using a larger CTGR1 causes the time constant of the integrator to increase, so a longer pulse is required before the flash is terminated. 1 : 10 + C1 C2 COUT 100 μF 315 V VIN VOUT Detect ISET SW Control Block RSET ISW sense VPULLUP DONE CHARGE DONE VIN IGBT Driver TRIGGER1 A IGBT Gate GATE RTGR1 100 kΩ PNZ121S Phototransistor TRIGGER2 CTGR1 1 μF GND A It is recommend to use a regulated system voltage for the bias. If battery voltage is used, the ALS sensitivity will vary with battery voltage, and there would be a small leakage current even when the camera is turned off. Figure 9. ALS typical application VOUT C1 VOUT VTRIGGER2 VTRIGGER2 C2 C2 C3 VTRIGGER1 C3 VGATE C1 C4 t (A) VTRIGGER1 C2 C1 C2 C3 C3 C4 VGATE C1 C4 Common Parameters Symbol Parameter Units/Division C1 VOUT 50 V C2 VTRIGGER2 1V 5V C3 VTRIGGER1 C4 VGATE 5V t time 20 μs C4 t (B) Figure 10. Adaptive timing of photoflash. (A) Subject near to camera, and (B) subject far from camera. 13 Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com Mobile Phone Xenon Photoflash Capacitor Charger With IGBT Driver A8731 Transformer Selection 1. The transformer turns ratio, N, determines the output voltage: N = NS / NP , VOUT = 31.5 × N – Vd , (4) (5) where 31.5 is the typical value of VOUTTRIP , and Vd is the forward drop of the output diode. 2. The primary inductance, LP , determines the on-time of the switch: ton = (–LP / R ) × ln (1 – ISWlim × R /VIN) , (6) where R is the total resistance in the primary current path (including RSWDS(on) and the DC resistance of the transformer). If VIN is much larger than ISWlim × R, then ton can be approximated by: ton = ISWlim × LP /VIN . (7) The minimum pulse width for toff determines what is the minimum LP required for the transformer. For example, if ISWlim = 0.7 A, N = 10, and VOUT = 315 V, then LP must be at least 9 μH in order to keep toff at 200 ns or longer. These relationships are illustrated in figure 11. In general, choosing a transformer with a larger LP results in higher efficiency (because a larger LP means lower switch frequency and hence lower switching loss). But transformers with a larger LP also require more windings and larger magnetic cores. Therefore, a trade-off must be made between transformer size and efficiency. Component Selection Selection of the flyback transformer should be based on the peak current, according to the following table: IPeak Range 3. The secondary inductance, LS, determines the offtime of the switch. Given: LS / LP = N × N , then toff = (ISWlim / N) × LS /VOUT (8) = (ISWlim × LP × N) /VOUT . (9) ton LP (A) Supplier Part Number 0.4 to 1.0 TDK LDT565630T-002 14.5 0.5 to 1.2 TDK LDT565630T-003 10.5 LDT565620ST-203 8.2 0.7 to 1.0 TDK 0.7 to 1.2 Mitsumi 0.8 to 1.2 Tokyo Coil (μH) C5-KT2.2L 8.0 T-19-243 6.5 toff VSW ISW Vr tf VIN VIN ISW VSW tneg Figure 11. Pulse width relationship definitions. 14 Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com Mobile Phone Xenon Photoflash Capacitor Charger With IGBT Driver A8731 Package EJ, 3 mm x 3 mm 10-Contact DFN with Exposed Thermal Pad 0.30 3.00 ±0.15 0.85 0.50 10 10 3.00 ±0.15 1.64 3.10 A 1 2 1 11X D SEATING PLANE 0.08 C +0.05 0.25 –0.07 C C 2.38 PCB Layout Reference View 0.75 ±0.05 0.50 1 For Reference Only (reference JEDEC MO-229WEED) Dimensions in millimeters Exact case and lead configuration at supplier discretion within limits shown 2 0.40 ±0.10 1.64 B 10 2.38 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 SON50P300X300X80-11WEED3M); 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) 15 Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com Mobile Phone Xenon Photoflash Capacitor Charger With IGBT Driver A8731 Revision History Revision Revision Date Rev. 1 April 19, 2012 Description of Revision Miscellaneous format changes Copyright ©2008-2012, Allegro MicroSystems, Inc. Allegro MicroSystems, Inc. reserves the right to make, from time to time, such departures from the detail specifications as may be required to permit improvements in the performance, reliability, or manufacturability of its products. Before placing an order, the user is cautioned to verify that the information being relied upon is current. Allegro’s products are not to be used in life support devices or systems, if a failure of an Allegro product can reasonably be expected to cause the failure of that life support device or system, or to affect the safety or effectiveness of that device or system. The information included herein is believed to be accurate and reliable. However, Allegro MicroSystems, Inc. assumes no responsibility for its use; nor for any infringement of patents or other rights of third parties which may result from its use. For the latest version of this document, visit our website: www.allegromicro.com 16 Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com