RT9591

Preliminary RT9591 Smart Photoflash Capacitor Charger with IGBT Driver General Description The RT9591 is a highly integrated photoflash charging solution in digital and film cameras. It is targeted for applications that use either two AA batteries or a single lithium-ion battery. The RT9591 integrates a constant current controller for charging high voltage photoflash capacitor quickly and efficiently, an IGBT driver for igniting flash tube, and a voltage detector. Only a few external components are used to reduce PCB space and cost. RT9591 is available in VQFN-16L 3x3 package. Features 1.8V to 6.5V Battery Input Voltage Range Charges Any Size Photoflash Capacitor Adjustable Input Current Uses Standard Transformers Adjustable Output Voltage Charge Complete Indicator Built-in IGBT Driver for IGBT Application Built-in Voltage Detector 16-Lead VQFN Package RoHS Compliant and 100% Lead (Pb)-Free Applications Ordering Information RT9591 Package Type QV : VQFN-16L 3x3 (V-Type) Operating Temperature Range P : Pb Free with Commercial Standard G : Green (Halogen Free with Commercial Standard) Digital Still Camera Film Camera Flash Unit Camera Phone Flash Pin Configurations (TOP VIEW) GNDDRV 12 11 10 9 DRVOUT VDRV IMCD VDOUT FBVD Note : RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020. Suitable for use in SnPb or Pb-free soldering processes. 100% matte tin (Sn) plating. FB PGND EXT GND 1 2 3 4 VDD CS DRVIN CHARGE STAT VBAT Richtek Pb-free and Green products are : 16 15 14 13 GND 17 5678 Marking Information For marking information, contact our sales representative directly or through a Richtek distributor located in your area, otherwise visit our website for detail. VQFN-16L 3x3 Patent Pending DS9591-07 August 2007 www.richtek.com 1 RT9591 Typical Application Circuit Delta 86A-3145 T1 1 : 15 CIN R6 1.5M 10uF SW AO3400 Q1 Preliminary VBAT 1.8V to 6.5V VOUT GSD2004S + COUT 100uF/ 300V Flash-Tube R1 150k 0805 10 VBAT IMCD EXT R7 1M VDD 3.3V 1uF 16 8 5 3 FBVD VDD 5V R8 100k 6 RT9591 VDOUT 7 Strobe DRVIN 14 11 VDRV 12 13 1 R2 150k 0805 DRVOUT GNDDRV GND 9 CS STAT CHARGE 2 PGND 0.1uF FB R4 1M R5 2M 15 4 R3 1k Figure 1. Photoflash Capacitor Charger Application VBAT 1.8V to 6.5V ASATECH ST-532553A T1 1 : 14 CIN 10uF SW AO3400 Q1 VOUT GSD2004S + COUT 47uF/ 300V Flash-Tube R1 150k 0805 10 16 3 VBAT EXT 8 FBVD VDD 5V 14 12 13 1 VDD 3.3V 1uF 5 R8 100k 6 RT9591 7 DRVIN 11 VDRV DRVOUT GNDDRV Strobe 0.1uF R2 150k 0805 VDOUT GND 9 CS STAT CHARGE 2 PGND IMCD FB 15 4 R4 560k R3 1k Figure 2. Photoflash Capacitor Charger Application for Low Charging Current Patent Pending www.richtek.com 2 DS9591-07 August 2007 Preliminary RT9591 VOUT VBAT 1.8V to 6.5V R5 1.5M Delta 86A-3145B T1 1 : 15 CIN 10uF 1 14 GSD2004S + SW AO3400 Q1 1 COUT 100uF/ 300V Flash-Tube R1 19k VBAT FBVD VDD EXT 8 5 IMCD R6 1M VDD 3.3V 16 3 10 5V 14 1uF R7 100k 6 RT9591 7 DRVIN 11 VDRV DRVOUT 12 Strobe 0.1uF VDOUT GND 9 CS STAT CHARGE 2 PGND GNDDRV FB 13 1 R3 1M R4 2M 15 4 R2 1k Figure 3. Photoflash Capacitor Charger Application with Center-Tap Transformer Patent Pending DS9591-07 August 2007 www.richtek.com 3 RT9591 Function Block Diagram VBAT Preliminary Charging Block VDD Constant Peak Current Control 1M One Shot Charging Block Enable Q S CHARGE GND FBVD 1.0V Reference DRVIN IGBT Driver VDRV DRVOUT GNDDRV One Shot Voltage Detector HV Detector FB VDOUT Latch R S Q Driver EXT PGND VDD CS +36mV 3.6Ω IMCD Chip Enable Latch R Functional Pin Description Pin No. 1 2 3 4 5 6 Pin Name FB PGND EXT GND VDD Feedback Voltage Pin. Power Ground. Output Pin for driving external NMOS on Flyback topology. Ground. Power Input Pin of RT9591. Charge Enable Pin, the charge function is executed when CHARGE pin is set from CHARGE Low to High. And the RT9591 gets into Shutdown mode when CHARGE pin is set to Low. 7 8 9 10 11 12 13 14 15 16 STAT FBVD VDOUT IMCD VDRV Charge Status Output. Open Drain output. When target output voltage is reached, N-MOSFET turns off. This pin needs a pull up resistor. Voltage Detector Feedback Pin. Voltage Detector Output Pin, Open Drain output. Minimum Current Detection Pin. IGBT Driver Power Pin. Pin Function DRVOUT IGBT Driver Output Pin. GNDDRV IGBT Driver Ground Pin. DRVIN CS VBAT IGBT Driver Input Pin. Input Current Setting Pin. Battery Supply Voltage Input Pin. The exposed pad must be soldered to a large PCB and connected to GND for maximum power dissipation. Exposed Pad (17) GND Patent Pending www.richtek.com 4 DS9591-07 August 2007 + STAT Preliminary Absolute Maximum Ratings (Note 1) RT9591 Supply Voltage, VDD, VBAT, VDRV -------------------------------------------------------------------------------- −0.3V to 7V EXT -------------------------------------------------------------------------------------------------------------------- −0.3V to (VDD + 0.3V) DRVOUT -------------------------------------------------------------------------------------------------------------- −0.3V to (VDRV + 0.3V) IMCD ------------------------------------------------------------------------------------------------------------------ −0.5V to 7V Other I/O Pin Voltage ---------------------------------------------------------------------------------------------- −0.3V to 7V Power Dissipation, PD @ TA = 25°C VQFN-16L 3x3 ------------------------------------------------------------------------------------------------------ 1.67W Package Thermal Resistance VQFN-16L 3x3, θJA ------------------------------------------------------------------------------------------------- 60°C/W Junction Temperature ---------------------------------------------------------------------------------------------- 150°C Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------ 260°C Storage Temperature Range ------------------------------------------------------------------------------------- −65°C to 150°C ESD Susceptibility (Note 2) HBM (Human Body Mode) --------------------------------------------------------------------------------------- 2kV MM (Machine Mode) ----------------------------------------------------------------------------------------------- 200V Electrical Characteristics (VDD = 3.3V, VVDRV = 3.3V, TA = 25°C, Unless Otherwise specification) Parameter VDD Operating Voltage VDD UVLO Rising VDD UVLO Hysteresis VBAT Voltage Rising VBAT UVLO Hysteresis FB Voltage Symbol VDD Test Conditions Min 1.8 -30 Typ -1.6 60 1.6 300 0.98 --1 0.01 0.01 10 3 3 16 Max 6.5 1.8 -1.81 -1 8 7 10 1 1 12 6 6 19 Units V V mV V mV V mV mV uA uA uA mA Ω Ω Ω VBAT(MIN) -190 VFB ｜ΔVFB｜ 1.8V< VDD < 3V 3V < VDD < 6.5V 0.96 -----8 VDD = 3.3V VDD = 3.3V VDD = 3.3V ---- Line Regulation Switch-Off Current Switch-Off Current Shutdown Current IVDD+IVBAT EXT On Resistance to VDD EXT On Resistance to GND STAT On Resistance to GND IVDD_SW_OFF VFB = 1.1V IVBAT_SW_OFF VFB = 1.1V IOFF Charge pin = 0V, VDD = 4.5V Minimum Current on Secondary Side IIMCD To be continued Patent Pending DS9591-07 August 2007 www.richtek.com 5 RT9591 Parameter Charge Input High Threshold Charge Input Low Threshold Minimum Off Time IGBT Driver IGBT Driver Supply Voltage DRVIN Input High Threshold DRVIN Input Low Threshold DRVOUT On Resistance to VVDRV DRVOUT On Resistance to GND Propagation Delay (Rising) Propagation Delay (Falling) Voltage Detector Voltage Detector Trip (Falling) VDOUT On Resistance to GND VFBVD VVDRV Symbol Preliminary Test Conditions Min -0.4 VBAT = 1.8V to 6.5V VDD = 1.8V to 6.5V 280 Typ 0.7 0.7 360 Max 1.3 -430 Units V V ns 2.0 -0.4 VVDRV = 3.3V VVDRV = 3.3V VBAT = 1.8V to 6.5V VDD = 1.8V to 6.5V VVDRV = 2V to 6.5V(Note 3) FBVD Falling VDD = 3.3V ----- -1.0 1 6 6 --- 5.5 1.3 -8 8 20 200 V V V Ω Ω ns ns 0.96 -- 0.99 16 1.02 19 V Ω Note 1. Stresses listed as the above "Absolute Maximum Ratings" may cause permanent damage to the device. These are for stress ratings. 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 remain possibility to affect device reliability. Note 2. Devices are ESD sensitive. Handling precaution recommended. Note 3. VDRV is the IGBT gate driving power. Therefore, setting VDRV voltage must consider IGBT gate threshold voltage, and its driving capability. Patent Pending www.richtek.com 6 DS9591-07 August 2007 Preliminary Typical Operating Characteristics 10.0 9.0 RT9591 Charge Time vs. VBAT (47uF COUT) 4.5 4.0 3.5 Charge Time vs. VBAT (100uF COUT) VOUT = 0V to 300V COUT = 100uF VDD = 3.3V 1 8.0 7.0 VOUT = 0V to 300V COUT = 47uF VDD = 3.3V Charge Time (s) Charge Time (s) 3.0 2.5 2.0 1.5 1.0 0.5 0.0 6.0 5.0 4.0 3.0 2.0 1.0 0.0 1.8 2.8 3.8 4.8 5.8 6.8 IPK-PRI = 1A IPK-PRI = 1A IPK-PRI = 1.5A IPK-PRI = 1.5A 1.8 2.8 3.8 4.8 5.8 6.8 VBAT (V) VBAT (V) Efficiency vs. Output Voltage 90 85 Secondary Minimum Current vs. Temperature 11.0 VIN = 5V VIN = 2.5V VIN = 3.3V Secondary Minimum Current (mA) IPK-PRI = 1.5A COUT = 100uF VDD = VBAT = VIN 10.5 10.0 9.5 9.0 8.5 8.0 7.5 7.0 6.5 6.0 -50 -25 0 25 50 75 100 125 ) Efficiency (%) 80 75 70 65 60 55 50 50 100 150 200 250 300 VIN = 1.8V Output Voltage (V) Temperature (°C) Output Voltage vs. Temperature 350 340 350 340 Output Voltage vs. Input Voltage VDD = VIN VBAT = VIN TA = 25°C VOUT set 300V Output Voltage (V) Output Voltage (V) 330 320 310 300 290 280 270 260 250 -50 -25 0 25 50 75 100 125 330 320 310 300 290 280 270 260 250 1.8 2.8 3.8 4.8 5.8 6.8 Temperature (℃ ) °C) Patent Pending DS9591-07 August 2007 Input Voltage (V) www.richtek.com 7 www.richtek.com 8 I PRI (1A/Div) VSW (10V/Div) VOUT = 100V VOUT = 300V RT9591 Output Voltage (100V/Div) STAT (2V/Div) I PRI (1A/Div) VSW (10V/Div) Time (1us/Div) Time (1us/Div) STAT & Output Voltage Preliminary Patent Pending VSW is the drain-to-source voltage of NMOS. I SEC (50mA/Div) VOUT = 300V VSW & Primary Current VSW is the drain-to-source voltage of NMOS. VSW & Primary Current Time (1s/Div) VSW (10V/Div) I SEC (50mA/Div) VSW (10V/Div) VOUT = 100V VSW & Secondary Current VSW & Secondary Current Time (1us/Div) Time (1us/Div) DS9591-07 August 2007 VSW is the drain-to-source voltage of NMOS. VSW is the drain-to-source voltage of NMOS. Preliminary Application Information The RT9591 integrates a constant peak current controller for charging photoflash capacitor, an IGBT driver for igniting flash tube, and a voltage detector with open drain output to provide a cost effective photoflash solution. The photoflash capacitor charger uses constant primary peak current and constant secondary valley current control to efficiently charge the photoflash capacitor. Pulling the CHARGE pin high initiates the charging cycle. During ON time, the primary current ramps up linearly according to VBAT and primary inductance. A resistor connecting to CS pin determines the ON time of primary NMOS and consequently the primary peak current. During the OFF time, the energy stored in the flyback transformer is boosted to the output capacitor. The secondary current decreases linearly at a rate determined by the secondary inductance and the output voltage (neglecting the voltage drop of the diode). The secondary current is monitored by the IMCD pin. When the secondary current drops below 10mA, ON time starts again. The charging cycle repeats itself and charges the output voltage. The output voltage is sensed by a voltage divider connecting to the anode of the rectifying diode. When the output voltage reaches the desired voltage set by resistor divider, the HV detector will terminate the charging cycle, disable the charging block and pull high the STAT pin. The voltage sensing path is cut off when charging completed to minimize the output voltage decay. Both the CHARGE and STAT pins can be easily interfaced to a microprocessor in a digital system. Transformer The flyback transformer should be appropriately designed to ensure effective and efficient operation. 1. Turns Ratio The turns ratio of transformer (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 the following formula: VOUT: Target Output Voltage RT9591 VDS(MAX): Maximum drain to source voltage of NMOS 2. Primary Inductance Each switching cycle, energy transferred to the output capacitor is proportional to the primary inductance for a constant primary current. The higher the primary inductance is, the higher the charging efficiency will be. Besides, the RT9591 has a 360ns minimum-off time for correct current and voltage sensing. To ensure the charger operating in continuous conduction mode, the primary inductance should be high enough according to the following formula: -9 LPRI ≥ 430 x 10 VOUT N x IPK - PRI VOUT: Target Output Voltage N : Transformer turns ratio IPK-PRI : Primary peak current 430 x 10−9 : The maximum value of minimum-off time. 3. Leakage Inductance and Parasitic Capacitance The leakage inductance of the transformer results in the first spike voltage when NMOS turns off as shown in Figure 4. 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. Wellcoupling winding design decreases the leakage inductance. However, well-coupling winding design usually results in large parasitic capacitance between windings. The parasitic capacitance consequently causes initial current swing when NMOS turns on as shown in Figure 5. Trade off is necessary between leakage inductance and parasitic capacitance. N(MIN) ≥ VOUT VDS(MAX) - VBAT Patent Pending DS9591-07 August 2007 www.richtek.com 9 RT9591 Spike voltage Preliminary Spike Voltage @Switching The peak reverse voltage of the diode is approximately: VPK-R ≈ VOUT + (N x VBAT) The peak current of the diode equals primary peak current divide transformer turn ratio as the following equation: IPK-SEC = IPK-PRI/N Note: N is transformer turns ratio. VSW (10V/Div) I PRI (1A/Div) NMOS The NMOS is the switching component of the flyback converter. Select adequate drain to source voltage and NMOS turn ON drain current is very important. For the RT9591 typical application circuit, If VOUT = 300V, VBAT = 6.5V, transformer turn ratio N = 15. VDS(MIN) = 300/15 + 6.5 = 26.5V. The NMOS minimum drain to source voltage should be greater than 26.5V. Time (250ns/Div) Figure 4 Swing Current @Switching VSW (20V/Div) Swing Current In addition, make sure that VDD is higher than VGS(th) (Gate threshold voltage) so as to sufficiently turn on the MOSFET. Capacitor X5R ceramic capacitor ≥ 10uF/10V is recommended for input capacitor to well decouple the switching current. Figure 6 and Figure 7 compare the input current waveforms with different input capacitors. I PRI (1A/Div) Time (1us/Div) Figure 5 Input Average Current & Output Voltage 4. Transformer Secondary Capacitance Any capacitance on the secondary can severely affect the efficiency. A small secondary capacitance is multiplied by N2 when reflected to the primary side. This capacitance forms a resonant circuit with the primary leakage inductance of the transformer. Therefore, both the primary leakage inductance and secondary side capacitance should be minimized. Rectifying Diode The rectifying diode should be with short reverse recovery time (small parasitic capacitance). Large parasitic capacitance increases switching loss and lowers charging efficiency. In addition, the peak reverse voltage and peak current of the diode should be sufficient. www.richtek.com 10 Input Average Current (500mA/Div) VBAT = 3.3V CIN = 4.7uF Output Voltage (100V/Div) Time (1s/Div) Figuer 6 Patent Pending DS9591-07 August 2007 Preliminary Input Average Current & Output Voltage Input Average Current (500mA/Div) VBAT = 3.3V CIN = 10uF RT9591 Adjustable Output Voltage The RT9591 senses output voltage by a voltage divider connecting to the anode of the rectifying diode during OFF time. This eliminates power loss at voltage-sensing circuit when charging completed. R3 to (R1+R2) ratio determines the output voltage as shown in the application circuit Figure1. The feedback reference voltage is 0.98V. If VOUT = 300V, in Figure 1 Photoflash Capacitor Charger Application according to the following equation: VOUT = VFB × (1+ R1+ R2 R3 ), so R1+ R2 R3 = 305 Output Voltage (100V/Div) Time (1s/Div) Figure 7 Adjustable Input Current The RT9591 simply adjusts peak primary current by a resistor RCS connecting to CS pin as shown in Function Block Diagram. RCS paralleled with internal 1MΩ resistor determines the ON time of primary NMOS. During the ON time, the primary current ramps linearly with a slope = VBAT/LPRI. Consequently, the current setting resister (RCS) could be calculated as: Ra = (IPK - PRI − 8 x 10 -3 x N) x LPRI 30 x 10 -12 1M x Ra (Ω) 1M − Ra R3 is recommend 1KΩ; R1 and R2 are used 150KΩ for reducing parasitic capacitance coupling effect of FB pin. R1 and R2 MUST be greater than 0805 size resister for enduring secondary HV. Lower Charging Current at Low Battery Voltage The RT9591 integrates a voltage detector with open drain output. This voltage detector is specially designed for lowering peak primary current and minimizing the impact to battery voltage at low VBAT condition as shown in Figure 8. The voltage detector senses VBAT through a resister divider R6 and R7 and compares it with internal 1V reference voltage. When the sensed voltage is lower than the reference voltage, VDOUT pin goes low and changes the resistance connecting to CS pin and the ON time. For example, if R6 equal 1.5MΩ and R7equal 1MΩ, VDOUT pin change status form open to ground when VBAT voltage under 2.5V. And current setting resister R4 and R5 can set different resistance for different input current when VBAT voltage under detector voltage. Figure 9 shows the lower charging current waveform. When VBAT voltage under 2.5V, the input average current become approximately 600mA to 460mA. RCS = Where IPK-PRI is the primary peak current and N is the turns ratio of transformer. Users could select appropriate RCS according to the battery capability and required charging time. Minimum IPK-PRI Limitation The IPK - PRI setting must ≥ 430 x 10 -9 x VOUT , N x LPRI where 430 x 10-9 is the maximum value of minimum off time. If lower IPK-PRI setting limitation is required, you may change transformer to incease N x LPRI product. Patent Pending DS9591-07 August 2007 www.richtek.com 11 RT9591 V BAT Preliminary T1 1 : 15 V OUT + C IN 10uF R6 1.5M Q1 R1 150k 100uF/3 00V C OUT FBVD VDD V DD 10uF R8 100k VBAT RT9591 VDOUT STAT CHARGE PGND DRVOUT GNDDRV GND CS FB IMCD EXT R7 1M R2 150k DRVIN VDRV R4 1M R5 2M R3 1k Figure 8. Lower Charging Current Application Circuit Lower Charging Current (1V/Div) Under 2.5V Δt Δt (200mA/Div) VBAT Input Average Current Output Voltage ΔV DRVIN Change input current ΔV Δt ≥ 2.5 V μs (100V/Div) Figure 10. IGBT Driver Input Signal Time (1s/Div) Figure 9 IGBT Driver Input Signal The slew rate of IGBT driver input DRVIN should be higher than 2.5V/μs for normally triggering the IGBT as shown in Figure 10. Layout Guide 1.Both of primary and the secondary power paths should be as short as possible. 2.Keep FB node area small and far away from nodes with voltage switching to reduce parasitic capacitance coupling effect. 3.The NMOS ground and feedback ground should be connect to VBAT ground for reduce switching noise. Patent Pending www.richtek.com 12 DS9591-07 August 2007 Preliminary Outline Dimension SEE DETAIL A L 1 RT9591 D D2 E E2 1 1 2 e A A1 A3 b 2 DETAIL A Pin #1 ID and Tie Bar Mark Options Note : The configuration of the Pin #1 identifier is optional, but must be located within the zone indicated. Symbol A A1 A3 b D D2 E E2 e L Dimensions In Millimeters Min 0.800 0.000 0.175 0.180 2.950 1.300 2.950 1.300 0.500 0.350 0.450 Max 1.000 0.050 0.250 0.300 3.050 1.750 3.050 1.750 Dimensions In Inches Min 0.031 0.000 0.007 0.007 0.116 0.051 0.116 0.051 0.020 0.014 0.018 Max 0.039 0.002 0.010 0.012 0.120 0.069 0.120 0.069 V-Type 16L QFN 3x3 Package Richtek Technology Corporation Headquarter 5F, No. 20, Taiyuen Street, Chupei City Hsinchu, Taiwan, R.O.C. Tel: (8863)5526789 Fax: (8863)5526611 Richtek Technology Corporation Taipei Office (Marketing) 8F, No. 137, Lane 235, Paochiao Road, Hsintien City Taipei County, Taiwan, R.O.C. Tel: (8862)89191466 Fax: (8862)89191465 Email: marketing@richtek.com DS9591-07 August 2007 www.richtek.com 13