High Efficiency Step-up DC/DC Converter control Asynchronous Boos

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High Efficiency Step-up DC/DC Converter control Asynchronous Boos

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PS0021
High Efficiency Step-up DC/DC Converter
control Asynchronous Booster Efficiency Quiescent Supply Current: Zero Shutdown current Output Voltage Accuracy: Fixed Output Voltage Provides 20mA from single cell Input Voltage Range: 0.8V 5.5V Startup Voltage 0.9V SOT-23 SOT-26 Package Wireless mice, keyboard Pagers Remote Controls Wireless Headsets Wireless Transmitters Personal Medical Devices Digital Still Cameras MP3/MP4 Players Single-Cell Battery-Powered Devices Low-Power Hand-Held Instruments PS0021 compact, high-efficiency, step-up DCDC converters available tiny, 3-pin thin SOT23 6-pin thin SOT26 packages. They feature extremely quiescent supply current ensure highest possible light-load efficiency. Optimized operation from alkaline nickel-metal-hydride (NiMH) cells, single cell, these devices ideal applications where extremely quiescent current ultra-small size critical. PS0021 also feature proprietary noisereduction circuitry, which suppresses electromagnetic interference (EMI) caused inductor many step-up applications. family offers different combinations fixed outputs, shutdown, reduction (see Selector Guide). unique design optimized high efficiency light load condition.
DESCRIPTION
APPLICATIONS
TYPICAL APPLICATION CIRCUIT
July 2007
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PS0021
CONFIGURATION
DESIGNATOR
Name VOUT Type Switch Low-Battery Detector Input. Enable Battery Detector Output Ground Power Supply Function Connect inductor between Battery. Connect resistive divider from Battery ground. EN=High: normal operation. (Supports both CMOS Logic). Open-Drain Output. Low-Battery Detector Output when VLBI less than Power Ground VOUT supplies power Step-up converter.
Note Limits 100% production tested +25°C. Limits over operating temperature range guaranteed design. Note Guaranteed with addition Schottky MBR0520L external diode between when using PS0021 with only cell, assumes 0.3V voltage drop across Schottky diode (see Figure Note Supply current measured with ammeter between output pin. This current correlates directly with actual battery supply current, reduced value according step-up ratio efficiency. Note VOUT forced following conditions inhibit switching: VOUT 1.05 VOUT (NOM) VOUT 3.465V
July 2007
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PS0021
BLOCK DIAGRAM
ABSOLUTE MAXIMUM RATINGS
OUT, SHDN, BATT, -0.3V -0.3V (VOUT 0.3V) OUT, Current Continuous Power Dissipation +70°C) 6-Pin Thin SOT26 (derate 7.1mW/°C above +70°C) .571mW Operating Temperature Range .-40°C +85°C Junction Temperature .+150°C Storage Temperature Range .-65°C +150°C Lead Temperature (soldering, 10s) +300°C
July 2007
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PS0021
ELECTRICAL CHARACTERISTICS
VBATT 1.2V, VOUT 3.3V, VOUT VOUT (NOM), SHDN OUT, +85°C, unless otherwise noted. Typical values +25°C.) Parameter Operating Input Voltage Output Voltage variation Minimum Startup Input Voltage Hold Voltage Switch leakage N-Channel On-Resistance Maximum oscillating freq Duty ratio Efficiency Quiescent Current into switching) Quiescent Current into Shutdown Current into SHDN Voltage Threshold SHDN Input Bias current Symbol VOUT load RDS(ON) FOSC DMAX Measured from voltage inductor current during time VOUT forced VOUT (NOM) 0.95 VOUT forced VOUT (NOM) 0.95 VIN= VOUT +0.5V measurement input current(VOUT pin) (Notes VOUT forced VOUT (NOM) 0.95 (Notes VSHDN 5.5V Conditions Note Unit
Battery Detector
voltage threshold input hysteresis input current output voltage output leakage current VOUT forced VOUT (NOM)*1.05 VOUT forced VOUT (NOM)*1.05 VOUT forced VOUT (NOM)*1.05 Force 20mA into LBO= 6.0V 0.45 0.02 0.50
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PS0021
TYPICAL OPERATING CHARACTERISTICS
(All specifications =+25°C, 1.5V, circuit typical application circuit, unless otherwise specified.)
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PS0021
TYPICAL OPERATING CHARACTERISTICS (continued)
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PS0021
TYPICAL OPERATING CHARACTERISTICS (continued)
July 2007
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PS0021
TYPICAL OPERATING CHARACTERISTICS (continued)
July 2007
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PS0021
OPERATION
PS0021 compact, high-efficiency, synchronous boost converter SOT-26 package designed spacerestricted applications. part available with adjustable output voltages ranging from 2.5V 5.0V. able start with input voltages 0.8V operate with input voltages down 0.5V. With internal synchronous rectifier on-resistance internal NMOS switch, device maintains high efficiency over wide range load current. shown Block Diagram, PS0021 consists accurate band core, error amplifier, start-up oscillator control logic unit along with PMOS NMOS switches. With current mode control, PS0021 ultra-fast line improved load regulation. Moreover, PS0021 provides real shutdown circuitry which disconnects output from input during shutdown results discharge output ground. Thermal overload protection limits total power dissipation PS0021. When junction temperature exceeds +145°C, thermal sensor signals shutdown logic turns most internal circuitry. thermal sensor turns internal circuitry again after IC's junction temperature drops 15°C. Thermal overload protection designed protect PS0021 event fault condition. continuous operation, exceed absolute maximum junction temperature rating +125°C.
Thermal Overload Protection
Current Limit Protection
PS0021 includes current limiter that monitors peak inductor current through NMOS switch turns NMOS switch when inductor peak current exceeds 150mA.
PS0021 starts typically 0.8V. When turned device gets start bias from VIN. start-up oscillator, which runs typically KHz, takes output voltage high enough that VOUT exceeds VIN. Once VOUT exceeds VIN, internal bias switches from VOUT internal bias-select circuit. Thus, once started (i.e. VOUT exceeds VIN), internal circuit bias completely independent VIN. start-up oscillator runs duty cycle around 650KHz. Once VOUT exceeds (typically 1.9V), start-up oscillator disabled normal fixed operation takes over.
Start-Up Mode
Light Load Operation
PS0021 provides improved light load efficiency. internal zero current comparator monitors inductor current load shuts PMOS switch once this current reduces some value (typically 50mA). This prevents inductor current from reversing polarity, avoiding back-charging thus improving efficiency light loads. that time, both NMOS PMOS switches remain off. However, normal operation starts again when output voltage falls below regulation point. automatically skips pulses light load, thus providing better efficiency.
Internal PMOS NMOS Switches
PS0021 features 0.45 NMOS switch PMOS switch. normal operation, these switches alternatively turned thus initiate charging inductor from then discharging output capacitor load. However, between event switch turning other turning dead time provided avoid huge in-rush current from output ground switches. During dead time, both switches remain inductor discharges body diode PMOS switch output.
July 2007
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PS0021
Under Voltage Lockout
When supply becomes (typically below 1.8V), PS0021 produces internal UVLO (Under Voltage Lockout) signal that disables normal operation enables start-up oscillator fixed frequency. this stage, very circuits operational. When oscillator raises supply above 1.9V, UVLO signal disabled normal mode takes over operation start-up oscillator. This mechanism protects chip from producing false logic input supply.
PS0021 features active-high CMOS input enable (SHUTB) that allows on/off control regulator. When SHUTB=Low, shutdown chip occurs that time almost quiescent current (<1µA) flows. output capacitor completely discharged through load feedback resistors real output shutdown. discharge switch internally connected between Enable (SHUTB) input TTL/CMOS compatible. Connect SHUTB normal operation.
Enable Input
Track Mode
track mode Vout follows Vin. Difference between Vout determined load current schottky forward voltage drop that current.
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PS0021
PACKAGE INFORMATION
July 2007
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PS0021
DISCLAIMERS
LIFE SUPPORT Power IC's products designed used components devices intended support sustain human life. Power IC's products components intended surgical implants into body other applications, which failure Power IC's products could create situation where personal death injury occur, authorized without express written approval Power IC's Chief Executive Officer. Power will held liable damages claims resulting from products medical applications. MILITARY Power IC's products designed military applications. Power IC's products military applications authorized without express written approval Power IC's Chief Executive Officer. Power will held liable damages claims resulting from products military applications. RIGHT MAKE CHANGES Power reserves right change this document and/or this product without notice. Customers advised consult their Power sales representative before ordering.
July 2007
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High Efficiency Step-up DC/DC Converter control Asynchronous Boos

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