GENERAL DESCRIPTION
The AP8801 is a compact PWM step-up DC/DC converter that operates from an input voltage as low as 1.0 Volt. The low start-up input voltage makes AP8801 specially designed for portable devices from one or two cell battery, delivering up to 250mA load current at VIN=2.5V Vout=3.3V. On-chip phase compensation and soft start circuits ensure excellent transient response and improved performance.
FEATURES
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1.0V Low Start-up Input Voltage at 1mA Load Deliver 100mA at 3.3V with 1V Input Voltage 90% High Efficiency (Vin 3.0V/Vout 3.3V) Output Voltage Accuracy (No load current) Vout 3.3V: (3.3V ± 82mV) Vout 5.0V: (5.0V ± 125mV)
300KHz Fixed Switching Frequency 0.5uA Low Shutdown Current
3-pin SOT-89 and 5 pin SOT-89 Package RoHS Compliant and 100% Lead (Pb)-Free
Low Start-up Voltage Step-up DC-DC Converter Anwell Semiconductor Corp.
The device features a voltage mode PWM control loop and an internal low turn-on resistance NMOS power switch, providing stable and high-efficiency operation over a broad load current range. High frequency 300KHz switching allows the use of small size external components. APPLICATION The AP8801 devices are available in both SOT-89 -3 and SOT-89-5 packages with standard regulated output voltage. Adjustable output voltage type in SOT-89-5 package is also available.
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DSC PDA
MP3 Players
Electronic Games Camcorders Portable Devices
Single-and Dual-Cell Battery Operated Products
TYPICAL APPLICATION
Fig 1. AP8801 Typical Application for 3.3V Output
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AP8801 Series
ORDERING INFORMATION
Vout Code：
Low Start-up Voltage Step-up DC-DC Converter Anwell Semiconductor Corp.
33：3.3V 50：5.0V Default : Adjustable Output
Temperature Range：
P：Commercial Standard, Lead (Pb) Free
and Phosphorous (P) Free Package
Package Code：
X：SOT-89-3
L：SOT-89-5
PIN CONFIGURATIONS
PACKAGE MARKING INFORMATION
Part Number Marking
AP8801-33PL AP8801-33PL AP8801-50PL AP8801-50PL AP8801-PL AP8801-PL AP8801-33PX AP8801-33PX AP8801-50PX AP8801-50PX
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AP8801 Series
PIN DESCRIPTION
Pin No.
SOT-89-5 SOT-89-3
Low Start-up Voltage Step-up DC-DC Converter Anwell Semiconductor Corp.
Symbol Description Chip enable. Set CE pin to low to shutdown the device. Must be set
1 - CE to Vout or higher voltage to enable the device. Do not float this pin.
For SOT-89 package, this pin is shorted to Vout internally.
2 2 Vout IC power supply pin. Connect this pin to the regulator output.
No Connection for fixed output type. Feedback input pin for
3 - NC or FB adjustable output type. Connect resistive divider tap here.
4 1 GND Ground. 5 3 LX Switch pin. Connect inductor/diode here.
FUNCTIONAL BLOCK DIAGRAM
Vout-+ErrorAmplifierRampGenerator,OSCPhaseCompensationVLXLimiterLX
-+PWMComparatorBufferDriverVoltageReferenceCESoft Start,Chip EnableGND
Fig 2. AP8801 Simplified Function Block Diagram
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AP8801 Series
TYPICAL APPLICATION CIRCUIT
Low Start-up Voltage Step-up DC-DC Converter Anwell Semiconductor Corp.
Fig 3. AP8801PL application for adjustable voltage output
Fig 4. AP8801PL application for high voltage output
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AP8801 Series
ABSOLUTE MAXIMUM RATINGS
Low Start-up Voltage Step-up DC-DC Converter Anwell Semiconductor Corp.
=
=
Supply Voltage -------------------------------------------------------------------------------------------- -0.3V to 10V
LX Pin Switch Voltage ----------------------------------------------------------------------------------- -0.3V to (Vout +0.3V) FB Pin Voltage --------------------------------------------------------------------------------------------- -0.3V to (Vout +0.3V) CE Pin Voltage -------------------------------------------------------------------------------------------- -0.3V to (Vout +0.3V) LX Pin Switch Current ----------------------------------------------------------------------------------- 1.2A Continuous power dissipation, PD @ TA = 25˚C
SOT-89 ------------------------------------------------------------------------------------------- 0.55W Package Thermal Resistance
SOT-89-3, θJA ------------------------------------------------------------------------------------ 180˚C /W Maximum Operating Junction Temperature ------------------------------------------------------- 150˚C Operating temperature range -------------------------------------------------------------------------- -20˚C to +70˚C Storage temperature range, TSTG -------------------------------------------------------------------- -55˚C to +150˚C Lead temperature (soldering, 10sec) ---------------------------------------------------------------- 260˚C ESD ratings
Human Body Model, per MIL-STD-883D-3015.7 ------------------------------------------ 1.25KV Machine Model, MIL-STM5.2-1999 ----------------------------------------------------------- 200V
ELECTRICAL CHARACTERISTICS
(VIN=2.5V, Vout =3.3V, Load Current=0, TA=25˚C, unless otherwise noted.) Symbol PARAMETER CONDITIONS
VST Start-up Voltage VST Start-up Voltage VHOLD Holding Voltage Vout IDD IDD1 IDD2 IOFF VREF
DMAX VLXLIM
Operating Vout Range Output Voltage
Switch On Current (Vout) Switch Off Current (Vout) Shutdown Current (VIN) Feedback Reference Voltage CE Input Voltage Threshold Maximum Duty Cycle Switch Voltage Limit
IL = 1mA IL = 100mA IL = 20mA
For adjustable output type Preset Vout = 3.3V Preset Vout = 5.0V Vout = Preset Output*0.95 Vout = Preset Output*1.1 CE = 0V, VIN = 4.5V
VIN = 2.5V, IL1~100mA
MIN TYP MAX UNITS-- -- -- 2.5 3.218 4.875 -- -- 0.2 --
0.95 1.20 0.70 3.3 5.0 50 90 35 0.5 0.6 90 0.6
1.10 1.30 -- 6.0 3.3825.125 -- -- 1 1.4 --
V V V V V V μA μA μA μA V V % Ω V
No Load Supply Current (Vout) With External Components
1.220 1.25 1.280
FSW Switching Frequency RDS(on) Switch ON Resistance ΔVLINE Line Regulation ΔVLOAD Load Regulation
-- 300 -- KHz 0.4 -- VIN = 1.5~2.5V, IL1mA 10 mV/V
0.25 mV/mA
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AP8801 Series
TYPICAL OPERATING CHARACTERISTICS
(VIN=+2.5V, Vout=3.3V, L1=10μH, C2=47μF, TA=+25℃, unless otherwise noted.)
3.3V VOUT Efficiency10090807060504030201000.1110Load Current (mA)
Low Start-up Voltage Step-up DC-DC Converter Anwell Semiconductor Corp.
5.0V VOUT Efficiency10090807060504030201000.1EFFI(%)EFFI(%)1V1.5V2.5V1.2V2V3V1V1.5V3V1.2V2V4V1001000110Load Current (mA)1001000
3.3V Output Voltage vs Load Current3.43.38Output Voltage (V)3.363.343.323.33.283.2601002003004005006007008009001000Load Current (mA)1V1.5V2.5V1.2V2V3V
5.0V Output Voltage vs Load Current5.15.05Output Voltage (V)54.954.94.854.84.750100200300Load Current (mA)4005001V1.5V3V1.2V2V4V
3.3V VOUT Start Up & hold Volatage
5.0V VOUT Start Up & hold Voltage1.4Start Up & hold Voltage(V)1.210.80.60.40.200204060Load Current (mA)80100Vstart(V)Vhold(V)1.41.2Start Up & holdVoltage(V)10.80.60.40.200204060Load Current (mA)80100Vstart(V)Vhold(V)
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AP8801 Series
3.3V Output Voltage vs Temperature
5.165.15Output Voltage (V)5.145.135.125.115.15.095.08-40-30-20-1001020304050607080Temperature (°C)5.0V Output Voltage vs TemperatureLow Start-up Voltage Step-up DC-DC Converter Anwell Semiconductor Corp.
3.373.365Output Voltage (V)3.363.3553.353.3453.343.335
3.33
-40-30-20-1001020304050607080
Temperature (°C)
No Load Current VS Input Voltage150No Load Current(uA)1301109070503011.52Input Voltage(V)2.533.3V5.0V
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AP8801 Series
DETAIL DESCRIPTION
The AP8801 is a high-efficiency, step-up DC-DC converter for portable devices like DSC and PDA. The AP8801 combines a boost switching regulator, 1.2A/0.4Ω N-channel power MOSFET, 1.25V precision reference, soft start, shutdown control, and a resistive divider for preset output. The switching DC-DC converter boosts a 1- to 4-cell input to a preset output between 2.5V and 6.0V. The two standard output voltages are 3.3V and 5V. Adjustable output voltage type is also available. The AP8801 starts from a low 1.0V input and remains operational down to 0.7V at 20mA load current.
voltage type AP8801PV by connecting FB pin to a resistive divider between the output and GND. The Vout can be set as:
Vout = (1+R1/R2) x 1.25V
Higher R1,R2 values reduce quiescent current, but give bad noise immunity. To keep stable feedback loop operation and better noise immunity, select (R1+R2) value less than 1MΩ
Low Start-up Voltage Step-up DC-DC Converter Anwell Semiconductor Corp.
Compensation
An internal phase compensation circuit is designed to guarantee stability over the full input/output voltage and full output load range.
Step-Up Converter
The step-up DC-DC converter operation can be understood by referring to the block diagram in Figure 2. The error amplifier monitors the output voltage by comparing the feedback voltage with the 1.25V reference voltage. When the feedback voltage is lower than the reference voltage, the error amplifier output will decrease. The error amplifier output is then compared with the oscillator ramp voltage at the PWM controller. When the ramp voltage is higher than the error amplifier output, the buffer driver is turned on which will then switch on the internal N-channel MOSFET; and vice versa. As the error amplifier output decreases, the buffer driver turn-on time increases and duty cycle increases. When the feedback voltage is higher than the reference voltage, the error amplifier output increases and the duty cycle decreases.
During the first part of each switching cycle, the internal N-channel MOSFET switch is turned on. This allows current to ramp up in the inductor and store energy in a magnetic field. During the second part of each cycle, the MOSFET is turned off, the voltage across the inductor reverses and forces current through the diode to the output filter capacitor and load. As the energy stored in the inductor is depleted, the current ramps down and the output diode turns off. The output filter capacitor stores the charge while the inductor current is higher than the output current, then sustains the output voltage until the next switching cycle.
Low-Voltage Start-Up Oscillator
The AP8801 use a CMOS, low-voltage start-up oscillator for a typically 1.0V startup input voltage at +25˚C. On start-up, the low-voltage oscillator switches the N-channel MOSFET until the output voltage reaches 2.2V. Above this level, the normal boost-converter feedback and control circuitry take over. Once the device is in regulation, it can operate down to a 0.7V input since internal power for the IC is bootstrapped from the output voltage. Do not apply full load until the output exceeds 2.4V.
Soft Start
The AP8801 has internal soft start circuit that limits current draw at startup, reducing transients on the input source. Soft-start is particularly useful for higher impedance input sources, such as Li+ and alkaline cells. When power is applied to the device, the soft start circuit first pumps up the output voltage to approximately 2.2 V at a fixed duty cycle. This is the voltage level at which the controller can operate normally. In addition to that, the start up capability with heavy loads is also improved.
Shutdown
The AP8801 enters shutdown to reduce quiescent current to typically 0.5μA when CE pin is low . For normal operation, drive CE high or connect CE to Vout. During shutdown, the reference, gain block, and all feedback and control circuitry are off. The boost converter’s output drops to one Schottky diode voltage drop below the input voltage and LX remains high impedance. The capacitance and load at Vout
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Output Voltage Selection
For adjustable output type referring to Fig. 3, select an output voltage for adjustable output
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AP8801 Series
determine the rate at which Vout decays. Shutdown can be pulled as high as 6V, regardless of the voltage at Vout.
which affect the efficiency are the forward voltage drop, VF, and the reverse recovery time. The forward voltage drop creates a loss just by having a voltage across the device while a current flowing through it. The reverse recovery time generates a loss when the diode is reverse biased, and the current appears to actually flow backwards through the diode due to the minority carriers being swept from the P–N junction. A Schottky diode with the following characteristics is recommended:
Small forward voltage, VF < 0.3 V Small reverse leakage current
Fast reverse recovery time/switching speed Rated current larger than peak inductor current Reverse voltage larger than output voltage
Low Start-up Voltage Step-up DC-DC Converter Anwell Semiconductor Corp.
APPLICATION INFORMATION
Inductor Selection
The AP8801 is designed to work well with a 4.7μH to 10μH inductor in most applications. Low inductance values supply higher output current, but also increase the ripple and reduce efficiency. Higher inductor values reduce ripple and improve efficiency, but also limit output current. Choose a low DC-resistance inductor, usually less than 1Ω to minimize loss. It is necessary to choose an inductor with saturation current greater than the peak current that the inductor will encounter in the application. Saturation occurs when the inductor’s magnetic flux density reaches the maximum level the core can support and inductance falls.
Layout Considerations
High switching frequencies make PC board layout a very important part of design. Good design minimizes excessive EMI on the feedback paths and voltage gradients in the ground plane, both of which can result in instability or regulation errors.
Connect the inductor, input filter capacitor, and output filter capacitor as close to the device as possible, and keep their traces short, direct, and wide to reduce power loss so as to improve efficiency. Connect their ground pins at a single common node in a star ground configuration, or at a full ground plane.
The external voltage feedback network should be very close to the FB pin, within 5mm. Keep noisy traces, such as the LX trace, away from the voltage feedback network; also keep them separate, using grounded copper. The output capacitor should be placed close to the output terminals to obtain better smoothing effect on the output ripple.
Capacitor Selection
Use a 47uF to 100uF SMT tantalum output capacitor with about 50mΩ to 150mΩ equivalent series resistance (ESR) to provide stable switching while minimizing output ripple. Smaller capacitors are acceptable for light loads or in applications that can tolerate higher output ripple. The input capacitor reduces peak currents and noise at the voltage source. Input capacitors must meet the input ripple requirements and voltage rating. The ESR of both input and output capacitors affects efficiency and output ripple. Output voltage ripple is the product of the peak inductor current and the output capacitor ESR. Use low ESR capacitors for best performance, or connect two or more output capacitors in parallel.
Schottky Diode Selection
The diode is the largest source of loss in DC–DC converters. The most important parameters
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AP8801 Series
PACKAGE OUTLINE
A) SOT-89
Low Start-up Voltage Step-up DC-DC Converter Anwell Semiconductor Corp.
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