Agamem Microelectronics Inc. PRELIMINARY AA18380 Switching Regulator Controller ■OVERVIEW The AA18380 is a single-channel PWM DC-DC regulator control IC that supports low-voltage operation. This IC features a low minimum operating voltage of 1.8 V and low current consumption, is optimal for use in high-efficiency power supplies for portable electronic equipment. ■FEATURES • Wide operating supply voltage range: 1.8 V to 15 V • Stable reference voltage circuit: 1.25V. • Low current consumption: Typically 5.5 mA in operation, 1 µA or less in stand-by • Wide PWM output frequency range: 10 kHz to 1 MHz • Incorporates a soft start circuit and adjustable soft start time. • Timer latch short-circuit protection circuit (SCP). • Low input voltage malfunction prevention circuit (U.V.L.O.) • On/off control function • Totem-pole type output by using an external resistor to set the output current (for NPN transistors) ■PIN Configuration (TOP VIEW) ○ IN- 1 SCP 2 7 OSC VCC 3 6 GND BR/CTL 4 5 OUT 8 FB ■APPLICATIONS • LCD Displays • PDAs • Digital Still Cameras • Hand-held and portable instruments ©Copyright Agamem Microelectronics Inc. 1 www.agamem.com.tw 2007/1/15 AA18380 Agamem Microelectronics Inc. PRELIMINARY Switching Regulator Controller ■PIN DESCRIPTIONS Pin No. Symbol I/O Description 1 IN- I 2 SCP — Soft start and short circuit protection setting capacitor connection pin 3 VCC — IC power supply pin 4 BR/CTL I Output current setting and control pin 5 OUT O Output voltage monitoring pin 6 GND — 7 OSC — 8 FB O Ground pin Timing capacitor & resistor connection pin for setting the internal PWM frequency Error amplifier output pin Internal error amplifier inverting input pin ■BLOCK DIAGRAM Vcc OSC 3 7 Reference Voltage Supply 1.25V 0.8V Sawtooth wave Oscillator 0.1V 0.1V IN- Error Amp. + 1 0.5V FB 5 OUT + PWM COMP. + + 36KΩ 500Ω Output drive Control circuit 30KΩ 0.3V DTC 0.6V 8 Soft start SCP 6 2 4 GND SCP BR/CTL ©Copyright Agamem Microelectronics Inc. 2 www.agamem.com.tw 2007/1/15 Agamem Microelectronics Inc. PRELIMINARY AA18380 Switching Regulator Controller ■ABSOLUTE MAXIMUM RATINGS (Ta = +25°C) Parameter Symbol Rating Condition Unit Min Max — 16 V — –50 mA — 50 mA Power supply voltage VCC Output source current IO+ Output sink current IO – Allowable dissipation PD Ta ≤ +25° C — 430* mW Operating temperature Top — –30 +85 Storage temperature Tstg –55 +125 °C °C — WARNING: Semiconductor devices can be permanently damaged by application of stress (voltage, current, temperature, etc.) in excess of absolute maximum ratings. Do not exceed these ratings. ■RECOMMENDED OPERATING RANGE (Ta = +25°C) Parameter Value Symbol Unit Min Typ Max VCC 1.8 — 15 V VI –0.2 — 1.0 V BR/CTL pin input voltage VBR –0.2 — VCC V Output source current IO+ –40 — — mA Output sink current IO – — — 40 mA SCP pin capacitance CPE — 0.1 — µ F Phase compensation capacitance CP — 0.1 — µ F 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 Power supply voltage Error amplifier input voltage ©Copyright Agamem Microelectronics Inc. 3 www.agamem.com.tw 2007/1/15 AA18380 Agamem Microelectronics Inc. PRELIMINARY Switching Regulator Controller ■ELECTRICAL CHARACTERISTICS (VCC = +2 V, Ta = +25° C) Parameter Circuit to prevent malfunction at low input voltage (U.V.L.O.) Symbol Value Condition Unit Min Typ Max — — 0.9 V 1.1 1.3 1.5 V –1.5 –1.0 –0.7 µ A 0.7 0.8 0.9 V –1.5 –1.0 –0.7 µ A Reset voltage VR Threshold voltage VTH Charging current ICS Soft start Voltage at soft start completion VtS Short circuit detection (S.C.P.) Charging current ICPC Threshold voltage Oscillation frequency Frequency input stability VtPC — 0.7 0.8 0.9 V fOCS RT = 3.0 kΩ , CT = 270 pF 400 500 600 kHz fdV VCC = 2 V to 15 V — 2 10 % Frequency variation with temperature fdT Ta = –30°C to +85°C — 5 — % Input threshold voltage VT VFB = 450 mV 480 500 520 mV VT input stability VTdV VCC = 2 V to 15 V — 5 20 mV VT variation with temperature VTdT Ta = –30°C to +85°C — 1 — % Input bias current IB –1.0 –0.2 1.0 µ A Voltage gain Frequency bandwidth AV 70 100 145 V/V — 6 — MHz 0.78 0.87 — V — 0.05 0.2 V — –40 –24 µ A 24 40 — µ A 65 75 85 % Sawtooth wave oscillator (OSC) Error amplifier Idle period adjustment section Maximum output voltage range BW VSCP = 0 V — VSCP = 0 V VIN = 0 V — AV = 0 dB VOM+ — VOM – Output source current Output sink current IOM – Maximum duty cycle tDUTY ©Copyright Agamem Microelectronics Inc. — IOM+ VFB = 0.45 V RT = 3.0 kΩ , CT = 270 pF VFB = 0.8 V 4 www.agamem.com.tw 2007/1/15 AA18380 Agamem Microelectronics Inc. PRELIMINARY Switching Regulator Controller (Continued) Parameter Symbol Output voltage Output section Output current setting section/ Control section Entire device Value Condition Unit Min Typ Max VOH1 RB = 390 Ω , IO = –15 mA 1.0 1.2 — V VOH2 RB = 750 Ω , VCC = 1.8 V IO = –10 mA 0.8 1.0 — V VOL1 RB = 390 Ω , IO = 15 mA — 0.1 0.2 V VOL2 RB = 750 Ω , VCC = 1.8 V IO = 10 mA — 0.1 0.2 V Output source current Output sink current IO+ RB = 390 Ω , VO = 0.9 V — –30 –20 mA IO – RB = 390 Ω , VO = 0.3 V 30 60 — mA Pull down resistance RO 20 30 40 kΩ Pin voltage VBR 0.2 0.3 0.4 V Input off condition IOFF –20 — 0 µ A Input on condition ION — — –45 µ A Pin current range IBR –1.8 — –0.1 mA Stand-by current ICCS BR/CTL pin open or VCC — — 1 µ A Average supply current ICC RB = 390 Ω — 5.5 9.3 mA — RB = 390 Ω — ■ TIMING DIAGRAM FB Pin voltage Reference input for short circuit detectioin compartor Idle Period setting voltage Sawtooth wave output Soft start setting voltage Out put waveform Stable State SCP pin waveform Soft start tS Output Short circuit ON-Power supply control SW OFF ©Copyright Agamem Microelectronics Inc. tPE Output short circuit Short circuit detection 5 www.agamem.com.tw 2007/1/15 Agamem Microelectronics Inc. PRELIMINARY AA18380 Switching Regulator Controller ■TYPICAL CHARACTERISTICS ©Copyright Agamem Microelectronics Inc. 6 www.agamem.com.tw 2007/1/15 Agamem Microelectronics Inc. PRELIMINARY ©Copyright Agamem Microelectronics Inc. AA18380 Switching Regulator Controller 7 www.agamem.com.tw 2007/1/15 Agamem Microelectronics Inc. PRELIMINARY ©Copyright Agamem Microelectronics Inc. AA18380 Switching Regulator Controller 8 www.agamem.com.tw 2007/1/15 Agamem Microelectronics Inc. PRELIMINARY AA18380 Switching Regulator Controller ■HOW TO SET THE TIME CONSTANT FOR SOFT START AND SHORT CIRCUIT DETECTION 1. Soft Start A soft start function, which gradually increases the width of the output pulses at power on, will be applied if a capacitor is connected to the SCP pin. This can prevent rush currents and overshoot when the power supply is turned on. At power on, the capacitor CPE connected to the SCP pin starts charging. The PWM comparator compares the soft start setting voltage as a proportion of the voltage at the SCP pin with the sawtooth waveform. The comparison controls the ON duty of the OUT pin, causing the soft start operation. On completion of soft start operation, the voltage at the SCP pin stays low, the soft start setting voltage stays high, and the circuit enters the output short circuit detection wait state. Soft start time (The time until the output ON duty reaches approximately 50%) tS [s] = 0.35 × CPE [µF] 2. Timer Latch Short Circuit Protection When the load conditions suddenly change due to load effect, the short-circuit protection comparator outputs the + high-level signal (VOM ) and the capacitor CPE connected to the SCP terminal starts charging. When the external capacitor CPE has been charged to approximately 0.8V, the latch circuit is set, the output terminal is fixed to low level, and the dead-time is set to 100%. However, the latch circuit is not reset unless the power for the latch circuit is turned off or restarted by the on/off control. • Short circuit detection time tPE [s] = 0.8 × CPE [µF] ■FUNCTIONAL DESCRIPTION 1. Switching Regulator Function (1) Reference voltage circuit This circuit is composed of a band gap circuit, and outputs a 1.25-volt temperature compensated reference voltage. This reference voltage is stabilized when the supply voltage is 1.8 V or higher. In addition to providing the reference voltage for the switching regulator, the circuit also sets the idle period. (2) Sawtooth wave oscillator This circuit generates a triangular wave like sawtooth with a peak of 0.8V (VOSCH) and a trough of 0.1V (VOSCL) using a capacitor (for the time constant) and resistor connected to the OSC pin (pin 7). The oscillator frequency can be set to any value by selecting appropriate values for the external capacitor and resistor, CT and RT. This oscillator can provide a frequency in the range 10 kHz to 1 MHz. fOSC = -1 VOSCL CT × RT × ln VOSCH 1 CT × RT = 0.48× [HZ] (3) Error amplifier This error amplifier detects and amplifies the DC-DC converter output voltage, and inputs that signal to a PWM comparator. The 0.5 V internal reference voltage is applied to the non-inverting input. Arbitrary gain and phase compensation can be connected by inserting a resistor and capacitor in series between the error amplifier output pin (pin 8) and the inverting input pin (pin 1). ©Copyright Agamem Microelectronics Inc. 9 www.agamem.com.tw 2007/1/15 AA18380 Agamem Microelectronics Inc. PRELIMINARY Switching Regulator Controller (4) PWM comparator The voltage comparator has one inverting and three non-inverting inputs. The comparator is a voltage/pulse width converter that controls the on-period of the output pulse according to its input voltage. The output transistors are turned on during periods when the OSC pin (pin 7) triangular waveform is lower than the error amplifier output voltage, soft start setting voltage, and idle period setting voltage. (5) Output driver The output circuit has a totem pole structure. A constant-current source output with line regulation can be set up at an arbitrary voltage by connecting a current setting resistor to the BR/CTL pin (pin 4). 2. Power Supply On/Off Function Stand-by mode (supply current 1 µA or less) can be set by connecting the BR/CTL pin (pin 4) to VCC or by making the pin open circuit. SW Mode AA18380 OFF Stand-by mode 4 RB ON SW Operating mode 3. Other Functions (1) Soft start and short circuit detection Soft start operation can be set by connecting capacitor CPE to the SCP pin (pin 2). Soft start prevents current spike and overshoot. When the soft start operation completes, the AA18380 enters the normal mode and enable short circuit detection function. When the output voltage drops, the error amplifier output is fixed at VOM+ and capacitor CPE starts charging. When it charges to above 0.8V, the output pin (pin 5) is set low and the SCP pin (pin 2) stays low. Once the protection circuit operates, the output latch circuit will not reset until power is restarted. (See “■ HOW TO SET THE TIME CONSTANT FOR SOFT START AND SHORT CIRCUIT DETECTION”.) (2) Circuit to prevent malfunction at low input voltage This circuit protects the system against degradation or destruction due to incorrect control operation when the power supply voltage falls during power on or power off. The low input voltage malfunction prevention circuit detects the internal reference voltage that changes with the supply voltage level. While the supply voltage is rising, On detection, the circuit fixes the output pin to low. The system recovers when the supply voltage rises back above the threshold voltage of the malfunction prevention circuit. ©Copyright Agamem Microelectronics Inc. 10 www.agamem.com.tw 2007/1/15 AA18380 Agamem Microelectronics Inc. PRELIMINARY Switching Regulator Controller ■TYPICAL APPLICATION EXAMPLE Boost Type - Step Up SCP Vcc BR/CTL 8 2 3 4 7 6 5 C1 0.1uF R6 390Ω Q2 2N7002 CTL-IN Vin (3V) C3 33uF 1 AA18380 IN- L1 22uH FB Vout (5V) 1N5821 OSC D1 GND R1 18KΩ OUT C6 10uF Q1 FZT489 C5 270pF C4 0.1uF R5 3KΩ R2 2KΩ Vout = 0.5 X (1 + R1/R2) Vout (5V) Buck Type - Step Down 2SA1585S 22uH 470Ω 1 SCP 2 Vcc 3 BR/CTL Vin (12V) 4 8 AA18380 33uF IN- 7 6 FB 2N3904 20KΩ OSC 2KΩ 47uF GND FR154 R2 5 OUT 2N3904 0.1uF 4.7KΩ R1 9KΩ 68pF 104pF 1KΩ 0.1uF 270pF 3KΩ 1.bootstrap, single end push pull style. 2.Vout = 0.5 X (1 + R1/R2) 3.For example, R1=5.6KΩ, R2=1KΩ, Vout=3.3V ©Copyright Agamem Microelectronics Inc. 11 www.agamem.com.tw 2007/1/15 Agamem Microelectronics Inc. PRELIMINARY AA18380 Switching Regulator Controller ■PC Board Layout Guideline PCB layout is very important for DC-DC operation. Please follow the notes and sample layout below. • Create a power ground island consisting of the input and output capacitor grounds and GND pins. Connect all of these together with short, wide traces or a small ground plane and isolate the IC ground from the power system. • Make the lines in the high-current loop as wide as possible and placing the inductor, rectifier diode, and output capacitors near the input capacitors and near the OUT and GND pins. • Position the input filter capacitor C3 as close as possible to the VCC and ground pins, and assure that there are no other paths for switching noise to enter the IC. • Keep the length of the line between the OUT pin and the switching device (MOSFET or other transistor) as short as possible to provide a clean switching pulse to the switching device. • The inductor and rectifier diode need to be close with OUT pin. • Place the feedback resistor – R2 as close to the IN1- pin as possible. The divider’s center trace should be kept short. Placing the resistors far away causes picking up switching noise. Avoid running the feedback trace near OUT pin. • Minimize the length and maximize the width of the traces between the output capacitors and the load for best transient responses. (Please refer to boost type application circuit for this PCB layout sample.) ■NOTES ON USE • The information described herein is subject to change without notice. • The specifications for the product described in this document are for reference only. Upon actual use, therefore, please request that specifications to be separately delivered. •The application circuit examples explain typical applications of the products, and do not guarantee the success of any specific mass-production design. • Application circuit diagrams and circuit constants contained herein are shown as examples of standard use and operation. Please pay careful attention to the peripheral conditions when designing circuits and deciding upon circuit constants in the set. • Take account of common impedance when designing the earth line on a printed wiring board. ©Copyright Agamem Microelectronics Inc. 12 www.agamem.com.tw 2007/1/15 AA18380 Agamem Microelectronics Inc. PRELIMINARY Switching Regulator Controller ■ORDERING INFORMATION Part number AA18380AP AA18380SP Package 8-pin Plastic TSSOP 8-pin Plastic SOP Remarks ■PACKAGE DIMENSIONS AA18380AP - 8-pin Plastic TSSOP E1 E L C AA18380AP theta D SYMBOLS A A1 A2 b C D E E1 e L y theta DIMENSIONS IN MILLIMETERS MIN NOM MAX ----1.20 0.05 --0.15 1.05 1.00 0.80 0.30 --0.19 0.20 --0.09 3.00 3.10 2.90 6.40 6.60 6.20 4.40 4.50 4.30 0.65 ----0.60 0.75 0.45 --0.10 ----8° 0° A2 A1 A 12°(4X) e b DIMENSIONS IN INCHES MIN NOM MAX ----0.048 0.002 --0.006 0.041 0.039 0.031 0.012 --0.007 0.008 --0.004 0.118 0.122 0.114 0.252 0.260 0.244 0.173 0.177 0.169 0.026 ----0.024 0.030 0.018 --0.004 ----8° 0° NOTE 1. PACKAGE BODY SIZES EXCLUDE MOLD FLASH PROTRUSIONS OR GATE BURRS 2. TOLERANCE +/-0.1 mm UNLESS OTHERWISE SPECIFIED 3. COPLANARITY : 0.1 mm 4. CONTROLLING DIMENSION IS MILLIMETER. CONVERTED INCH DIMENSIONS ARE NOT NECESSARILY EXACT. 5. FOLLOWED FROM JEDEC MO-153 ©Copyright Agamem Microelectronics Inc. 13 www.agamem.com.tw 2007/1/15 Agamem Microelectronics Inc. PRELIMINARY ©Copyright Agamem Microelectronics Inc. AA18380 Switching Regulator Controller 14 www.agamem.com.tw 2007/1/15