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UNISONIC TECHNOLOGIES CO., LTD P1786
PWM CONTROL 3A STEP-DOWN CONVERTER
DESCRIPTION
UTC P1786 consists of 3A step-down switching regulator control which include a reference voltage source, oscillation circuit, error amplifier, internal PMOS and etc with PWM. UTC P1786 can provide low-ripple power, high efficiency, and excellent transient characteristics. An enable function, an over current protect and short circuit protect function are built inside, so the operation frequency can be reduced from 300KHz to 30KHz when OCP or SCP happens. The PWM control circuit can vary the duty ratio linearly from 100 down to 0%. This converter also includes an error amplifier circuit as well as a soft-start circuit that prevents overshoot at startup. Also, to minimum external component counts for an internal compensation block is built in. These ICs can work as step-down switching regulators with the addition of an internal P-channel Power MOS, a coil, capacitors, and a diode connected externally. They provides such outstanding features: low current consumption. It is also suitable for the operation via an AC adapter because this converter accommodate an input voltage up to 23V.
LINEAR INTEGRATED CIRCUIT
SOP-8
*Pb-free plating product number: P1786L
FEATURES
* Input voltage: 3.6V ~ 23V * Output voltage: 0.8V ~ VCC * Duty ratio: 0% to 100% PWM control * Oscillation frequency: 300KHz typ. * Soft-start, current limit, enable function * Thermal shutdown function * Built-in internal SW P-channel MOS
ORDERING INFORMATION
Ordering Number Normal Lead Free Plating P1786-S08-R P1786L-S08-R P1786-S08-T P1786L-S08-T Package SOP-8 SOP-8 Packing Tape Reel Tube
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PIN CONFIGURATION
LINEAR INTEGRATED CIRCUIT
PIN DESCRIPTIONS
PIN NO. 1 2 3 4 5, 6 7, 8 PIN NAME FB EN OCSET VCC Output VSS I/O I I I O DESCRIPTION Feedback pin. Chip enable, H: enable step-down function L: chip disable Add an external resistor to set max output current. IC power supply pin Switch Pin. Connect external inductor/diode here. Minimize trace area at this pin to reduce EMI. GND Pin
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BLOCK DIAGRAM
LINEAR INTEGRATED CIRCUIT
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ABSOLUTE MAXIMUM RATINGS
LINEAR INTEGRATED CIRCUIT
PARAMETER SYMBOL RATING UNIT VCC Pin Voltage VCC VSS - 0.3 ~ VSS + 25 V Feedback Pin Voltage VFB VSS - 0.3 ~ VCC V EN Pin Voltage VEN VSS - 0.3 ~ VIN + 0.3 V Switch Pin Voltage VOUT VSS - 0.3 ~ VIN + 0.3 V Power Dissipation PD Internally limited Operating Temperature TOPR -20 ~ +125 Storage Temperature TSTG -40 ~ +150 Note: Absolute maximum ratings are those values beyond which the device could be permanently damaged. Absolute maximum ratings are stress ratings only and functional device operation is not implied.
THERMAL DATA
PARAMETER Thermal Resistance Junction-to-Ambient SYMBOL JA CONDITIONS MIN TYP MAX UNIT /W 65
ELECTRICAL CHARACTERISTICS (VIN = 12V, Ta=25C, unless otherwise specified)
PARAMETER SYMBOL Input Voltage VIN Feedback Voltage VFB Feedback Bias Current IFB(BIAS) Switch Current ISC Standby Current ISTN-BY Line Regulation VOUT /VOUT Load Regulation VOUT /VOUT Oscillation Frequency fOSC Frequency of Current Limit or Short Circuit fOSC1 Protect VSH EN Pin Input Voltage VSL EN Pin Input Leakage Current OCSET Pin Bias Current Soft-Start Time Internal MOSFET RDS(ON) Efficiency ISH ISL IOCSET TSS RDS(ON) VIN=5V, VFB=0V VIN=12V, VFB=0V VIN = 12V, VOUT = 5V, IOUT = 3A 75 0.3 CONDITIONS IOUT=0.1A IOUT=0.1A VEN =0V VIN = 5V~23V, IOUT=0.2A IOUT = 0.1 to 3A Measure waveform at SW pin Measure waveform at SW pin MIN TYP MAX UNIT 3.6 23 V 0.784 0.8 0.816 V 0.1 0.5 A 3.5 A 10 A 1 2 % 0.2 0.5 % 240 300 360 KHz 10 30 60 KHz V A A A ms m %
Evaluate oscillation at SW pin 2.0 Evaluate oscillation stop at SW pin 20 -10 90 2 110 70 91
0.8
105 5 150 100
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FUNCTION DESCRIPTION
LINEAR INTEGRATED CIRCUIT
PWM Control The UTC P1786 consists of DC/DC converters which employ a PWM system. In this DC/DC converter, the pulse width varies in a range from 0 to 100% which is according to the load current. Cause the switching frequency remains constant the ripple voltage which produced by the switching can be removed easily through a filter. Therefore, these converters provide a low-ripple power over broad ranges of input voltage and load current. Under Voltage Lockout The under voltage lockout circuit makes sure that the outputs of high-side MOSFET driver remain in the off state after the supply voltage drops below 3.3V. When VCC rises above 3.5V normal operation resumes. RDS(ON) Current Limiting The current limit threshold is fixed by the external resistor which is connected from VCC supply to OCSET. An over-current condition is triggered when the PWM voltage is less than the voltage at OCSET. ILOAD x RDS(ON) = IOCSET x ROCSET above formula is setting the current limit value.
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TEST CIRCUIT
LINEAR INTEGRATED CIRCUIT
+
-
TYPICAL APPLICATION CIRCUIT
VOUT L1 Value
VIN=12V, IMAX=3A 2.5V 3.3V 15uH 18uH
5V 22uH
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TYPICAL CHARACTERISTICS
Input Voltage vs. Frequency 350 Oscillation Frequency, Fosc (KHz) 345 340 335 325 320 315 310 305 300 0 VOUT=3.3V IOUT=0.2A 5 10 15 20 25 FB (V) 330 0.84 0.83 0.82 0.81 0.80 0.79 0.78 0.77 0.76 0.75 0.74
LINEAR INTEGRATED CIRCUIT
Input Voltage vs. FB
VOUT=3.3V IOUT=0.2A 0 5 10 20 15 Input Voltage, VIN (V) 25
Input Voltage, VIN (V)
Line Regulation 3.40 3.35 3.30 3.25 3.20 3.15 3.10 0 5 10 15 20 25 Input Voltage, VIN (V) VOUT=3.3V IOUT=0.2A 5.10 5.09 Output Voltage, VOUT (V) Output Voltage, VOUT (V) 5.08 5.07 5.06 5.05 5.04 5.03 5.02 5.01 5.00 0.0 VIN=12V 1.0
Load Regulation
2.0
3.0
4.0
Output Current, IOUT (A)
Efficiency (%)
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TYPICAL CHARACTERISTICS(Cont.)
LINEAR INTEGRATED CIRCUIT
UTC assumes no responsibility for equipment failures that result from using products at values that exceed, even momentarily, rated values (such as maximum ratings, operating condition ranges, or other parameters) listed in products specifications of any and all UTC products described or contained herein. UTC products are not designed for use in life support appliances, devices or systems where malfunction of these products can be reasonably expected to result in personal injury. Reproduction in whole or in part is prohibited without the prior written consent of the copyright owner. The information presented in this document does not form part of any quotation or contract, is believed to be accurate and reliable and may be changed without notice.
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