PS1541 PICSEMI | Alldatasheet
Document overview
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Technical content
FEATURES
On Board Power MOSFET Uses Tiny Capacitor And Inductors 12V at 150mA from 5V input Up to 92% Efficiency Operates with Input Voltage as Low as 2.5V and Output Voltage as High as 22V 620KHz Fixed Switching Frequency Low 1.1V Feedback Voltage Soft Start UVLO, Thermal Shutdown Internal Current Limit Available in SOT-26 packages.
APPLICATIONS
Cell Phones Handheld Computers and PDAs. Camera Phone Flash Small LCD Displays Digital Still and Video Cameras White LED Driver External Modems
DESCRIPTION
The PS1541 is a current mode step up converter intended for small, low power applications. The PS1541 switches over 600KHz and allows the use of tiny, low cost capacitors and inductors. Internal soft start results in small inrush current and extends battery life. The PS1541 operates from an input voltage as low as 2.5V and can generate 12V at up to 150mA from a 5V supply. The PS1541 includes under-voltage lockout, current limiting and thermal overload protection preventing damage in the event of an output overload. The PS1541 is available in small 6-pin SOT-26 package. TYPICAL APPLICATION CIRCUIT High Efficiency Step Up DC/DC Converter PS1541 July 2007 www.picsemi.com © 2007 Power IC. All Rights Reserved.
SW 1 Switch Connect inductor between SW and IN. GND 2 Ground Ground pin FB 3 Feedback Adjustable feedback input, connect to resistor voltage divider. EN 4 Enable input. EN=High: normal operation. (Supports both TTL and CMOS Logic). NC 5 Not connected IN 6 Battery input. Boost regulator input. July 2007 www.picsemi.com © 2007 Power IC. All Rights Reserved.
July 2007 www.picsemi.com © 2007 Power IC. All Rights Reserved.
Symbol Parameter Value Unit VSW DC Voltage at Pin 1 -0.5 to +28 V VEN Enable Input Voltage at Pin 2 -0.3 to +6.0 V PD Continuous Power Dissipation Internally limited W TSTG Storage Temperature Range -65 to +150 °C RθJA Thermal Resistance, Junction-To-Air 235 °C /W TJ,MAX Operating Junction Temperature -40 to +125 °C TL Lead Temperature (Soldering, 5sec) 260 °C PS1541 ESD ESD Capability, HBM model 2.0 kV RECOMMENDED OPERATING CONDITIONS Symbol Parameter Value Unit VIN DC Supply Voltage at Pin 1 +2.5 to 6 V VEN Enable Input Voltage at Pin 2 0 to VIN V TJ Operating Junction Temperature -40 to +125 °C July 2007 www.picsemi.com © 2007 Power IC. All Rights Reserved.
ELECTRICAL CHARACTERISTICS
( Vin = 2.5V, TA = +25°C, unless otherwise noted. Typical values are at TA = +25°C.) Symbol Parameter Test Condition Min Typ Max Units Vin Operating Input Voltage 2.5 5.5 V UVLO Under Voltage Lock-out Vin going Lo. 2.15 2.2 2.4 V Vout-max Maximum Output Voltage 25 V Iq Supply Current (quiescent) No Switching (Vin=5V, VFB= 1.25V) 135 260 μA Supply Current Switching FB=0 510 750 μA Ish Supply Current (shut- down) VEN =0 1 μA FOSC Operation Frequency 620 KHz DMAX Maximum Duty Cycle 93 % VFB Feedback Voltage 1.05 1.1 1.15 V Feedback Input Bias Current VFB=1.25V 7 nA RDS(ON) MOSFET ON resistance 0.8 Ω ILIM Current Limit Vin=3 2.3 A Turn ON 0.95 V VEN Enable Threshold Turn OFF 0.35 V IEN Enable Input Bias Current VEN =0, 5V 1 μA PS1541 Thermal Shut-down 145 °C July 2007 www.picsemi.com © 2007 Power IC. All Rights Reserved.
TYPICAL OPERATING CHARACTERISTICS Efficiency vs Load Current 100 0 50 100 150 200 Load (mA) Vin=5V, Vout=14V Eff (%) FB Voltage vs Temperature 1.07 1.075 1.08 1.085 1.09 - 4 0 - 2 00 2 04 06 08 0 Temp (°C) FB Voltage(V) Frquency vs Temperature 500 550 600 650 700 750 -50 0 50 100 150 Temperature (°C) Frequency (KHz) Temperature vs Duty Cycle 91.5 92.5 93.5 94.5 -40 -10 20 50 80 110 140 Temperature (°C) Duty Cycle (%) Temperature vs Supply Current 115 120 125 130 135 140 145 -40 -10 20 50 80 110 140 Temperature (°C) Supply Current (uA) July 2007 www.picsemi.com © 2007 Power IC. All Rights Reserved.
TYPICAL OPERATING CHARACTERISTICS (Continued) PS1541 July 2007 www.picsemi.com © 2007 Power IC. All Rights Reserved.
The PS1541 is a high efficiency, fixed frequency, peak current mode boost regulator. It has the architecture to regulate the voltage at the feedback pin, so that a regulated fixed current is achieved. The power MOS is turned ON through the control circuitry, at the start of each oscillator cycle and th us the charging phase is initiated. The error amplifier, consisting of a voltage comparator and current sense amplifier, is basically, a PWM comparator. The voltage comparator amplifies the difference between the reference and feed back voltage. When the output of the current sense amplifier, reaches the output of the voltage comparator, the POWER MOS is turned OFF and thus the charging phase is terminated. To prevent sub-harmonic osc illations at duty cycles greater than 50 percent, a stabilizing ramp is added to the current sense signal. In this way the peak current level keeps the output in regulation. The PS1541 has internal soft start mechanism, to limit the inrush current at startup and to limit the amount of overshoot on the output, also. An internal blanki ng time is provided during start up, to prevent the start of switching before all the circuitry become ready for operation. The current limit is increased by a fourth every 60µs giving a total soft start time of 240µs. Setting the Output Voltage Set the output voltage by selecting the resistive voltage divider ratio. Use 12k Ω for the low side resistor R2 of the voltage divider. Determine the high-side resistor R1 by the equation: R1= R2(VOUT - VFB)/VFB Where VOUT is the output voltage. Current Limit PS1541 Under Voltage Lockout When the input supply goes too low (below 2.2V) the PS1541 produces an internal UVLO (under voltage lockout) signal that shuts down the chip. This mechanism protects the chip from producing false logic due to low input supply. Thermal Overload Protection Thermal-overload protection limits total power dissipation in the PS1541. When the junction temperature exceeds T j= +145 °C, the thermal sensor signals the shutdown logic and turning off most of the internal circuitry. The thermal sensor turns internal circuitry on again after the IC’s junction temperature drops by 20 °C. The regulator then starts functioning in the required mode based on the supply voltage. The PS1541 includes a current limiter. It monitors the peak current through the inductor and controls gate of the power device. Enable Input The PS1541 features an active-high Enable input (EN) pin that allows on/off control of the regulator. The PS1541 bias current reduces to less than microampere when it is shutdown. The Enable input is TTL/CMOS compatible. Thermal-Overload protection is designed to protect the PS1541 in the event of a fault condition. For continual operation, do not exceed the absolute maximum junction temperature rating of Tj = +125°C. July 2007 www.picsemi.com © 2007 Power IC. All Rights Reserved.
PACKAGE INFORMATION
July 2007 www.picsemi.com © 2007 Power IC. All Rights Reserved.
Power IC’s products are NOT designed to be used as co mponents in devices intended to support or sustain human life. The use of Power IC’s products in components intended for surgical implants into the body or other applications, in which failure of Power IC’s products co uld create a situation where personal death or injury may occur, is NOT authorized without the express wri tten approval of Power IC’s Chief Executive Officer. Power IC will NOT be held liable for any damages or claims resulting from the use of its products in medical applications. MILITARY Power IC’s products are NOT designed for use in milit ary applications. The use of Power IC’s products in military applications is NOT authorized without the ex press written approval of Power IC’s Chief Executive Officer. Power IC will NOT be held liable for any damages or claims resulting from the use of its products in military applications. RIGHT TO MAKE CHANGES Power IC reserves the right to change this document and/or this product without notice. Customers are advised to consult their Power IC sales representative before ordering. July 2007 www.picsemi.com © 2007 Power IC. All Rights Reserved.