AT1450 Preliminary Product Information Photoflash Capacitor Charger for DSC Features General Description • 2.5 to 13 V supply voltage operating range. • Low current consumption: 6 mA in operation, • 20 kHz to 1 MHz operation frequency range. • Provides a fixed output current with minimal supply voltage fluctuations by using an external resistor to set the output current. • Totem-pole output. • Built-in soft start circuit. • Built-in auto-discharge function. The AT1450 is a single-channel PWM control IC for Photoflash capacitor charger with soft start function and auto-discharge circuit. Adjustable soft start is programmed with an external capacitor on SS pin. Applications •Digital Still Cameras flash unit Block Diagram Aimtron reserves the right without notice to change this circuitry and specifications. 2F, No.10, Prosperity RD. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 WWW: http://www.aimtron.com.tw Fax: 886-3-563-0879 Email: [email protected] 1 AT1450 Preliminary Product Information Photoflash Capacitor Charger for DSC Pin Configuration Ordering Information Part number AT1450S AT1450S_Green Package SOP8 SOP8,Green Marking AT1450S AT1450S, date code with one bottom line Pin Description Pin No. Symbol I/O 1 2 3 4 5 6 7 INSS VCC BR/CTL OUT GND OSC I — — I O — — 8 FB O Description Error amplifier inverting input Soft start setting capacitor connection Power supply Output current setting Totem-pole type output Ground Capacitor and resistor connection pin for setting the oscillation frequency Error amplifier output 2F, No.10, Prosperity RD. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 WWW: http://www.aimtron.com.tw Fax: 886-3-563-0879 Email: [email protected] 2 AT1450 Preliminary Product Information Photoflash Capacitor Charger for DSC Absolute Maximum Ratings (Ta=+250C) Parameter Power supply voltage Output source current Output sink current Allowable dissipation Operating temperature Storage temperature ESD Classification Symbol Condition VCC IO+ IOPD PD TOP TSTG — — — SOP-8, Ta ≦+25°C TSSOP-8, Ta ≦+25°C — — Rated Value Min. Max. — 15 — -50 — 50 — 570 — 430 -30 +85 -55 +125 MIL-STD-883 Class 2 Unit V mA mA mW mW 0 C 0 C * : When mounted on a 10 cm square double-sided epoxy board WARNING: Do not exceed these ratings. IC devices can be permanently damaged by stress (voltage, current, temperature, etc.) in excess of absolute maximum ratings. Recommended Operating Conditions (Ta=+250C) Parameter Symbol Values Unit Min. Typ. Max. Power supply voltage VCC 2.5 -13.5 Ｖ Error amplifier input voltage VI -0.2 -1.0 Ｖ BR/CTL pin input voltage VBR -0.2 -VCC Ｖ Output source current IO+ -20 --ｍＡ Output sink current IO--40 ｍＡ SS pin capacitance CPE -0.1 -μＦ Phase compensation capacitance CP -0.1 -μＦ Output current setting resistance RB 150 390 5000 Ω Timing resistance RT 1.0 3.0 10.0 ｋΩ Timing capacitance CT 100 270 10000 pF Oscillation frequency fOSC 10 500 1000 kHz Operating temperature TOP -30 +25 +85 °C WARNING: Recommended operating conditions are normal operating ranges for the IC device. All the device’s electrical characteristics are warranted for operation within these ranges. Use IC devices only within the recommended operating conditions. Operation outside these ranges may adversely affect the reliability and can result in device failure. 2F, No.10, Prosperity RD. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 WWW: http://www.aimtron.com.tw Fax: 886-3-563-0879 Email: [email protected] 3 AT1450 Preliminary Product Information Photoflash Capacitor Charger for DSC Electrical Characteristics (VCC=+3.0V, Ta=+250C) Parameter VCC Under voltage Reset voltage for Lockout falling Vcc. OUT (U.V.L.O.) remains off if Vcc is below this level. Startup voltage for rising Vcc. Soft start Charging current Voltage at soft start completion Invalid threshold voltage of SS Oscillation frequency Sawtooth waveform oscillator (OSC) Frequency input Stability Frequency variation with temperature Input threshold Voltage VT input stability Error amplifier Idle period adjustment section VT variation with Temperature Input bias current Voltage gain Frequency bandwidth Maximum output voltage range Output source current Output sink current Maximum duty cycle Output voltage Output section Output current Setting section/ Control section Symbol VR Values Unit Min. Typ. Max. -- 2.24 -- V -VTH ISS VSS 2.4 VSS=0V --- 2.5 2.6 V -1.5 -1.0 -0.7 μA 1.000 1.150 1.260 V -- 0.8 -- V fOSC RT=3kΩ, CT=270pF 400 500 600 kHz f∆V VCC=2.5V to 13.5V -- 2 10 % f∆T Ta =-300C to 850C -- 5 -- % VT VFB = 450mV 480 500 520 mV VT∆V VCC=2V to 13.5V -- 5 20 mV VT∆T Ta = -300C to 850C -- 1 -- % IB AV BW VOM+ VOM_ IOM+ IOM_ TDUTY VIN = 0V VOH1 VOH2 VOL1 VOL2 Output source current Output sink current Pull down resistance Pin voltage Input off condition Input on condition Pin current range Condition IO+ IORO VBR IOFF ION IBR -AV = 0 dB -- VFB = 450mV RT=3.3kΩ, CT=270pF fOSC = 500KHz RB= 390Ω, IO= -15 mA RB= 750Ω, VCC = 3.0V IO= -10 mA RB= 390Ω, IO= -15 mA RB= 750Ω, VCC = 3.0V IO= -10 mA RB= 390Ω, VO = 0.9V RB= 390Ω, VO = 0.3V -RB= 390Ω -- -1.0 -0.2 70 100 -6 0.78 0.87 -- 0.05 --40 24 40 -85 1.0 μA 145 V/V -- MHz -V 0.2 V -24 μA -- μA 87 % 1.0 0.8 1.2 1.0 --- V V --- 0.1 0.1 0.2 0.2 V V --40 -30 mA 40 70 -mA 20 30 40 ｋΩ 0.10 0.19 0.25 V -20 -0 μA ---45 μA -1.8 --0.1 ｍＡ 2F, No.10, Prosperity RD. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 WWW: http://www.aimtron.com.tw Fax: 886-3-563-0879 Email: [email protected] 4 AT1450 Preliminary Product Information Photoflash Capacitor Charger for DSC Stand-by current ICCS Average supply current ICC Entire device BR/CTL pin open or VCC RB= 390, VCC =2.5~13.5V -- -- 200 -- 6 10.0 ｍＡ μA Timing Chart 2F, No.10, Prosperity RD. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 WWW: http://www.aimtron.com.tw Fax: 886-3-563-0879 Email: [email protected] 5 AT1450 Preliminary Product Information Photoflash Capacitor Charger for DSC CH1:SS CH2:OUT Soft-Start and Auto Dis-Charge function CSS=1µF CSS=10µF 2F, No.10, Prosperity RD. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 WWW: http://www.aimtron.com.tw Fax: 886-3-563-0879 Email: [email protected] 6 AT1450 Preliminary Product Information Photoflash Capacitor Charger for DSC Typical Application Schematic 2F, No.10, Prosperity RD. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 WWW: http://www.aimtron.com.tw Fax: 886-3-563-0879 Email: [email protected] 7 AT1450 Preliminary Product Information Photoflash Capacitor Charger for DSC Functional Description Soft Start At power-on, the AT1450 enters the soft-start mode to prevent current spike and overshoot. The capacitor CS is charged from 0.2V at a constant current of 1µA. The soft-start time for the duty cycle t S ( s ) = 0.8 × CS ( µF ) Setting Oscillating Frequency The oscillator circuit generates a triangular sawtooth wave with a peak of 0.8V and a trough of 0.1V using the timing capacitor (CT) and the timing resistor (RT) that are connected to the OSC pin. This oscillator can provide oscillating frequency in the range from 20KHz to 1MHz. The waveform of the OSC pin is shown as Figure 2. Figure 2 Oscillator Waveform The cycle (T) can be determined as follows: VX ) VH T = −CT × RT × log e (0.1 / 0.8) = 2.1 × CT × RT [s ] VX = VHe − t CT × RT t = −CT × RT × log e ( Switching Regulator Function (1) Reference voltage circuit A temperature-compensated reference voltage (~1.25V) is generated by the reference voltage circuit from the voltage supplied by the power supply pin (pin 3). The circuit also sets the idle period besides providing the reference voltage for the switching regulator. 2F, No.10, Prosperity RD. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 WWW: http://www.aimtron.com.tw Fax: 886-3-563-0879 Email: [email protected] 8 AT1450 Preliminary Product Information Photoflash Capacitor Charger for DSC (2) Error amplifier The error amplifier detects the output voltage of the switching regulator and sets the PWM control signal. The voltage gain is fixed. The system is made stable by connecting a phase compensation capacitor to the FB pin (pin 8). (3) PWM comparator The voltage comparator includes one inverting and three non-inverting inputs. The comparator is a voltage to pulse width converter that controls the ON time of the output pulse depending on the level of input voltage. The output level remains high when the sawtooth wave is lower than the error amplifier output voltage, the soft start setting voltage, and the idle period setting voltage. (4) Output circuit The output circuit can drive an external NPN transistor directly and has a totem pole configuration. The value of the ON/OFF current can be set by a resistor connected to the BR/CTL pin (pin 4). Stand-by mode (supply current 1µA or less) can be set by connecting the BR/CTL pin (pin4) to VCC or by making the pin open. (5) Under-Voltage Lockout (UVLO) Transients during powering on or instantaneous glitches in the supply voltage can cause the control IC to malfunction and damage the system. To prevent malfunction at low input voltage, the circuit compares the supply voltage to the internal reference voltage to detect a low input voltage. Once detected, the circuit sets the output pin low. To cancel the status, set VCC below the reset voltage VR (0.9V) and then set VCC up to the recommended operation range and the latch will be restored to operate normally. 2F, No.10, Prosperity RD. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 WWW: http://www.aimtron.com.tw Fax: 886-3-563-0879 Email: [email protected] 9 AT1450 Preliminary Product Information Photoflash Capacitor Charger for DSC Small Outline SYMBOL A B C D E F H J K M L e1 α 8-pin Plastic SOL INCHES MIN MAX 0.188 0.197 0.149 0.158 0.228 0.244 0.050 BSC 0.013 0.020 0.004 0.010 0.053 0.069 0.011 0.019 0.007 0.010 0.016 0.050 0.150 REF 450 0 80 0 MILLIMETERS MIN MAX 4.80 5.00 3.80 4.00 5.80 6.20 1.27 BSC 0.33 0.51 0.10 0.25 1.35 1.75 0.28 0.48 0.19 0.25 0.40 1.27 3.81 REF 450 0 0 80 NOTES - 2F, No.10, Prosperity RD. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C. Tel: 886-3-563-0878 WWW: http://www.aimtron.com.tw Fax: 886-3-563-0879 Email: [email protected] 10