AT1380A Preliminary Product Information Switching Regulator Controller for LCD Bias Features General Description • 2.5 to 15 V supply voltage operating range. • Low current consumption: 6 mA in operation, 1 µA or less in stand-by. • 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 timer-latch short circuit detection and protection circuit (SCP). The AT1380A is a single-channel PWM control IC for DC/DC conversion with soft start function and short circuit detection. Adjustable soft start is programmed with an external capacitor on SCP pin. The AT1380A is ideal for up, down and flyback conversion. Applications • LCD Displays • PDAs • Digital Still Cameras 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 AT1380A Preliminary Product Information Switching Regulator Controller for LCD Bias Pin Configuration Ordering Information Part number AT1380AS AT1380AS_PBF AT1380AS_GRE AT1380AP AT1380AP_PBF AT1380AP_GRE Package SOP8 SOP8, Pb-Free SOP8, Green TSSOP8 TSSOP8, Pb-Free TSSOP8, Green Marking AT1380AS AT1380AS, Date Code with one bottom line AT1380AS, Date Code with two bottom line AT1380AP AT1380AP, Date Code with one bottom line AT1380AP, Date Code with two bottom line Pin Description Pin No. Symbol I/O 1 2 3 4 5 6 7 INSCP VCC BR/CTL OUT GND OSC I — — I O — — 8 FB O Description Error amplifier inverting input Soft start and SCP 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 AT1380A Preliminary Product Information Switching Regulator Controller for LCD Bias 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 — — MIL-STD-883 Rated Value Min. Max. — 15 — -50 — 50 — 570 — 430 -30 +85 -55 +125 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 SCP 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 AT1380A Preliminary Product Information Switching Regulator Controller for LCD Bias 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. Charging current Voltage at soft start completion Short circuit Charging current detection (S.C.P.) Threshold voltage Oscillation frequency Sawtooth waveform Frequency input oscillator (OSC) Stability Frequency variation with temperature Input threshold Voltage VT input stability VT variation with Temperature Input bias current Error amplifier Voltage gain Frequency bandwidth Maximum output voltage range Output source current Output sink current Idle period Maximum duty cycle adjustment section Soft start Output voltage Output section Symbol VR Values Unit Min. Typ. Max. -1.8 1.9 V -VTH ICS Vts VSCP=0V ICPC VtPC fOSC f∆V VSCP=0V f∆T Ta =-300C to 850C VT VFB = 450mV -- -RT=3kΩ, CT=270pF VCC=2.5V to 13.5V VT∆V VT∆T VCC=2V to 13.5V Ta = -300C to 850C IB AV BW VOM+ VOM_ IOM+ IOM_ TDUTY VIN = 0V VOH1 VOH2 VOL1 VOL2 Output source current Output sink current Pull down resistance Condition IO+ IORO -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 -- 2.4 2.5 2.6 V -1.5 0.7 -1.0 0.8 -0.7 0.9 μA V -1.5 0.7 400 -- -1.0 0.8 500 2 -0.7 0.9 600 10 μA V kHz % -- 5 -- % 480 500 520 mV --- 5 1 20 -- mV % -1.0 -0.2 70 100 -6 0.78 0.87 -- 0.05 --40 24 40 75 -- 1.0 μA 145 V/V -- MHz -V 0.2 V -24 μA -- μA 85 % 1.0 0.8 1.2 1.0 --- V V --- 0.1 0.1 0.2 0.2 V V -40 20 -40 70 30 -30 -40 mA mA ｋΩ 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 AT1380A Preliminary Product Information Switching Regulator Controller for LCD Bias Output current Setting section/ Control section Pin voltage Input off condition Input on condition Pin current range Stand-by current VBR IOFF ION IBR ICCS Average supply current ICC Entire device 0.10 0.19 0.25 V -20 -0 μA ---45 μA -1.8 --0.1 ｍＡ BR/CTL pin open or --1 μA VCC RB= 390, -6 10.0 ｍＡ VCC =2.5~13.5V RB= 390Ω -- 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 AT1380A Preliminary Product Information Switching Regulator Controller for LCD Bias 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] 6 AT1380A Preliminary Product Information Switching Regulator Controller for LCD Bias 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 AT1380A Preliminary Product Information Switching Regulator Controller for LCD Bias Functional Description Soft Start SCP Figure 1. Soft-Start SCP circuit At power-on, the AT1380A enters the soft-start mode to prevent current spike and overshoot. The capacitor CS is charged from 0V at a constant current of 1µA. The soft-start time for the duty cycle t S = 0.8 × CS ( µF ) When VSCP reaches 0.8V, the AT1380A leaves the soft-start mode to enter the normal mode and enable the SCP function. If the output load conditions change rapidly causing the output to drop suddenly, the external capacitor CS will start to charge because the error amplifier output (FB pin) is fixed at VOM+. When the external capacitor is charged above 0.8V, the output pin is set low. Once the latch circuit has set, the capacitor CS will be discharged to low state and the latch circuit will not reset until power is turned off or the power supply is restarted. Short-circuit detection time (or full soft-start time) : t PE = 0.8 × CS ( µF ) 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 AT1380A Preliminary Product Information Switching Regulator Controller for LCD Bias 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. (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 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 AT1380A Preliminary Product Information Switching Regulator Controller for LCD Bias 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] 10 AT1380A Preliminary Product Information Switching Regulator Controller for LCD Bias 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] 11 AT1380A Preliminary Product Information Switching Regulator Controller for LCD Bias Small Outline SYMBOL A B C D E F H K M α 8-pin TSSOP INCHES MIN MAX 0.114 0.122 0.169 0.177 0.244 0.260 0.026 BSC 0.010 0.012 0.002 0.006 0.041 0.047 0.005 BSC 0.020 0.028 80 00 MILLIMETERS MIN MAX 2.90 3.10 4.30 4.50 6.20 6.60 0.65 BSC 0.25 0.30 0.05 0.15 1.05 1.20 0.127 BSC 0.50 0.70 00 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] 12