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Agamem Microelectronics Inc. PRELIMINARY
OVERVIEW
AA18380
Switching Regulator Controller
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 A 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) INSCP VCC BR/CTL 1 2 3 4 8 FB 7 OSC 6 GND 5 OUT
APPLICATIONS
* LCD Displays * PDAs * Digital Still Cameras * Hand-held and portable instruments
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PIN DESCRIPTIONS
Pin No. 1 2 3 4 5 6 7 8 Symbol INSCP VCC BR/CTL OUT GND OSC FB I/O I -- -- I O -- -- O
AA18380
Switching Regulator Controller
Description
Internal error amplifier inverting input pin Soft start and short circuit protection setting capacitor connection pin IC power supply pin Output current setting and control pin Output voltage monitoring pin Ground pin Timing capacitor & resistor connection pin for setting the internal PWM frequency Error amplifier output pin
BLOCK DIAGRAM
Vcc 3 OSC 7
Reference Voltage Supply
1.25V
0.8V 0.1V
Sawtooth wave Oscillator
0.1V IN1 Error Amp. + 0.5V FB 8 36K + PWM COMP. + + DTC 0.6V 30K
5 OUT
500
Output drive Control circuit
0.3V
Soft start SCP
6 GND 2 SCP 4 BR/CTL
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ABSOLUTE MAXIMUM RATINGS
AA18380
Switching Regulator Controller
(Ta = +25C)
Parameter Power supply voltage Output source current Output sink current Allowable dissipation Operating temperature Storage temperature
Symbol VCC IO+ IO - PD Top Tstg
Condition Min -- -- Ta +25 C -- -- -- -- -30 -55
Rating Max 16 -50 50 430* +85 +125
Unit V mA mA mW
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 = +25C) Parameter Power supply voltage Error amplifier input voltage BR/CTL pin input voltage Output source current Output sink current SCP pin capacitance Phase compensation capacitance Output current setting resistance Timing resistance Timing capacitance Oscillation frequency Operating temperature Symbol Min VCC VI VBR IO+ IO - CPE CP RB RT CT fOSC TOP 1.8 -0.2 -0.2 -40 -- -- -- 150 1.0 100 10 -30 Value Typ -- -- -- -- -- 0.1 0.1 390 3.0 270 500 +25 Max 15 1.0 VCC -- 40 -- -- 5000 10.0 10000 1000 +85 k pF kHz V V V mA mA F F Unit
C
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ELECTRICAL CHARACTERISTICS
AA18380
Switching Regulator Controller
(VCC = +2 V, Ta = +25 C)
Parameter Circuit to prevent malfunction at low input voltage (U.V.L.O.) Soft start Short circuit detection (S.C.P.) Reset voltage Threshold voltage Charging current Voltage at soft start completion Charging current Threshold voltage Oscillation frequency Frequency input stability Frequency variation with temperature Input threshold voltage VT input stability VT variation with temperature Input bias current Voltage gain Frequency bandwidth Error amplifier Maximum output voltage range Output source current Output sink current Idle period adjustment section Maximum duty cycle
Symbol VR VTH ICS VtS ICPC VtPC fOCS fdV fdT VT VTdV VTdT IB AV BW VOM+ VOM - IOM+ IOM - tDUTY
Condition Min -- -- VSCP = 0 V -- VSCP = 0 V -- RT = 3.0 k , CT = 270 pF VCC = 2 V to 15 V Ta = -30C to +85C VFB = 450 mV VCC = 2 V to 15 V Ta = -30C to +85C VIN = 0 V -- AV = 0 dB -- 1.1 -1.5 0.7 -1.5 0.7 400 -- -- 480 -- -- -1.0 70 -- 0.78 -- VFB = 0.45 V RT = 3.0 k , CT = 270 pF VFB = 0.8 V -- 24 65
Value Typ -- 1.3 -1.0 0.8 -1.0 0.8 500 2 5 500 5 1 -0.2 100 6 0.87 0.05 -40 40 75 Max 0.9 1.5 -0.7 0.9 -0.7 0.9 600 10 -- 520 20 -- 1.0 145 -- -- 0.2 -24 -- 85
Unit V V A V A V kHz % % mV mV % A V/V MHz V V A A %
Sawtooth wave oscillator (OSC)
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(Continued) Parameter Symbol VOH1 VOH2 Output voltage Output section Output source current Output sink current Pull down resistance Pin voltage Output current setting section/ Control section Input off condition Input on condition Pin current range Stand-by current Entire device Average supply current VOL1 VOL2 IO+ IO - RO VBR IOFF ION IBR ICCS ICC -- RB = 390
AA18380
Switching Regulator Controller
Value Min Typ 1.2 1.0 0.1 0.1 -30 60 30 0.3 -- -- -- -- 5.5 Max -- -- 0.2 0.2 -20 -- 40 0.4 0 -45 -0.1 1 9.3 V V V V mA mA k V A A mA A mA 1.0 0.8 -- -- -- 30 20 0.2 -20 -- -1.8 -- -- Unit
Condition RB = 390 , IO = -15 mA RB = 750 , VCC = 1.8 V IO = -10 mA RB = 390 , IO = 15 mA RB = 750 , VCC = 1.8 V IO = 10 mA RB = 390 , VO = 0.9 V RB = 390 , VO = 0.3 V --
BR/CTL pin open or VCC RB = 390
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 ON-Power supply control SW OFF Output Short circuit tPE Output short circuit Short circuit detection
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TYPICAL CHARACTERISTICS
AA18380
Switching Regulator Controller
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AA18380
Switching Regulator Controller
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AA18380
Switching Regulator Controller
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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 x CPE [F]
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 x CPE [F]
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
(3) Error amplifier
-1 VOSCL CT x RT x ln VOSCH
0.48x
1 CT x RT
[HZ]
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).
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(4) PWM comparator
AA18380
Switching Regulator Controller
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 A or less) can be set by connecting the BR/CTL pin (pin 4) to VCC or by making the pin open circuit. SW OFF Mode
AA18380
Stand-by mode
4 RB
ON
Operating mode
SW
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.
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TYPICAL APPLICATION EXAMPLE
AA18380
Switching Regulator Controller
Boost Type - Step Up
INSCP Vcc Vin (3V) C3 33uF BR/CTL 1 8 FB OSC GND OUT L1 22uH 1N5821 D1 R1 18K Q1 FZT489 C4 0.1uF R2 2K C6 10uF Vout (5V)
2 3 4
AA18380
7 6 5
C1 0.1uF R6 390 Q2 2N7002
C5 270pF
R5 3K
CTL-IN
Vout = 0.5 X (1 + R1/R2)
2SA1585S 22uH 470 33uF IN1 8 FB OSC GND FR154 5 OUT 2N3904 270pF 3K 0.1uF R2 1K 104pF 2N3904 68pF 20K 2K 47uF R1 9K
SCP 2 Vcc 3 BR/CTL Vin (12V) 0.1uF 4.7K 4
AA18380
7 6
1.bootstrap, single end push pull style. 2.Vout = 0.5 X (1 + R1/R2) 3.For example, R1=5.6K , R2=1K , Vout=3.3V
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Vout (5V)
Buck Type - Step Down
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PC Board Layout Guideline
AA18380
Switching Regulator Controller
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. (c)Copyright Agamem Microelectronics Inc.
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ORDERING INFORMATION
Part number AA18380AP AA18380SP Package 8-pin Plastic TSSOP 8-pin Plastic SOP
AA18380
Switching Regulator Controller
Remarks
PACKAGE DIMENSIONS
AA18380AP - 8-pin Plastic TSSOP
C
L
E1
AA18380AP
E
theta
12(4X)
A1
A2
A
D
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
e
b
SYMBOLS A A1 A2 b C D E E1 e L y theta
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
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AA18380
Switching Regulator Controller
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