3.7v升压5V1A,同步整流

深圳市百盛新纪元半导体有限公司Ｍｒ．郑：１８９４８３１９４２　　　ＱＱ：１０９４６４２９０７PS7516

EMI Certification2.5A High Efficiency Synchronous PWM Boost Converter

Description

The PS7516 is a high efficiency, fixed frequency 550KHz, current mode PWM boost DC/DC converter which could operate battery such as input voltage down to 1.9V. down to . The converter output voltage can be adjusted to a maximum of 5.25V by an external resistor divider. Besides the converter includes a 0.08Ω N-channel MOSFET switch and 0.12Ω P-channel synchronous rectifier. So no external Schottky diode is required and could get better efficiency near 96%. efficiency near 93%.

The converter is based on a fixed frequency, current mode, pulse-width-modulation PWM controller that goes automatically into PSM mode at light load. When converter operation into discontinuous mode, the internal anti-ringing switch will reduce interference and radiated electromagnetic energy. The PS7516 is available in a space-saving SOT-23-6 package for portable application.

Features

              

High Efficiency up to 96% (When Vin = 4.2V) High Efficiency up to 96%

Low RDS(ON) Integrated Power MOSFET NMOS 80mΩ / PMOS120mΩ

Wide Input Voltage Range: 1.9V to 5.5V Fixed 550KHz Switching Frequency

Low-Power Mode for Light Load Conditions ±2.0% Voltage Reference Accuracy

PMOS Current Limit for Short Circuit Protection Low Quiescent Current

Output Ripple under 200mV. (Scope Full Bandwidth)

Fast Transient Response Built-In Soft Start Function

Over-Temperature Protection with Auto Recovery Output Overvoltage Protection Space-Saving SOT-23-6 Package

Applications

   

Portable Power Bank Wireless Equipment Handheld Instrument GPS Receiver

Pin Assignments

SOT23-6

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INOUTEN615243LXGndFB

Figure 1. Pin Assignment of PS7516

Functional Pin Description

Pin Name LX G GndFB EN OUT IN INPin No. 1 2 3 4 5 6 Pin Function Power Switching Connection. Connect LX to the inductor and output rectifier. Ground Pin. Voltage Feedback Input Pin. Logic Controlled Shutdown Input. Output of the Synchronous Rectifier. Power Supply Input Pin. Vre 4.36gN

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PS7516

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Block Diagram

VINLXANTI-RINGOUTENOn/OffControlMOSBody-DiodeSwitchIsense/Current LimitSlope Comp.Anti-Reverse ComparatorPFMControlOSCOVPUVLOVINPWMControlLogicCOMP Error AmpFBBandgap ReferenceOTPGND

Figure 3. Block Diagram of PS7516

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PS7516

Typical Application Circuit

L1VIN2.5V to 5.5VC110μFC20.1μF10μHVOUT5V/1A1C4, C6 C60.1μFC C5, C522μFR1525K6VINPS7516GNDLX2OUT54ONOFFENFB3R2100K

Figure 2. Typical Application Circuit

Absolute Maximum Ratings (Note 1)

● Supply Voltage VIN --------------------------------------------------------------------------------------------- -0.3V to +6.5V ● LX Voltage VLX -------------------------------------------------------------------------------------------------- -0.3V to +6.5V ● All Other Pins Voltage ----------------------------------------------------------------------------------------- -0.3V to +6.5V ● Maximum Junction Temperature (TJ) --------------------------------------------------------------------- +150°C ● Storage Temperature (TS) ----------------------------------------------------------------------------------- -65°C to +150°C ● Lead Temperature (Soldering, 10sec.) ------------------------------------------------------------------- +260°C ● Package Thermal Resistance (θJA)

SOT-23-6 ---------------------------------------------------------------------------------------------- +250°C/W

● Package Thermal Resistance (θJC)

SOT-23-6 ---------------------------------------------------------------------------------------------- +130°C/W

Note 1：Stresses beyond this listed under “Absolute Maximum Ratings\" may cause permanent damage to the device.

Recommended Operating Conditions

● Supply Voltage VIN --------------------------------------------------------------------------------------------- +1.9V to +5.5V --------------------------------------------------------------------------------------------- + .V to +5.5V ● Output Voltage Range ---------------------------------------------------------------------------------------- up to +5.25V ● Operation Temperature Range ------------------------------------------------------------------------------ -40°C to +85°C

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Electrical Characteristics

(VIN=3.3V, TA=25°C, unless otherwise specified.) Parameter VIN Input Supply Voltage Input UVLO Threshold Under Voltage Lockout Threshold Hysteresis Supply Current Supply Current (Switching) Feedback Voltage High-Side PMOSFET RDS(ON) Low-Side NMOSFET RDS(ON) High-Side MOSFET Leakage Current Low-Side MOSFET Leakage Current Oscillation Frequency Switch Current Limit Short Circuit Trip Point Short Circuit Current Limit Maximum Duty Cycle Line Regulation Load Regulation OVP Threshold Voltage on OUT Pin OVP Threshold Hysteresis Internal Soft-Start Time EN Input Low Voltage EN Input High Voltage EN Input Current Thermal Shutdown Threshold (Note 2) Thermal Shutdown Hysteresis Note 2：Not production tested.

Symbol VIN VFB ILX(leak) FOSC DMAX VEN (L) VEN (H) IEN TSD VIN=3.3V 2.5V≦VIN≦5.5V VLX=5.5V, VOUT=0V VLX=5.5V VIN=3.3V Monitored FB voltage VIN = 3.3V VIN=3.3V VIN=2.5V to 5.5V, IOUT=100mA IOUT=0A to 1A 1.4 VIN Rising VIN Falling Conditions Min .91.. 0.784 450450 2.5 Typ 1.85 0.2 450.8 120 80 550 0.3 50 90 0.5 6 500 1 2 150 30 Max 5.5 0.816 10 10 650 1 3 0.4 Unit V V V μA V mΩ mΩ μA μA KHz A V mA % % % V mV ms V V μA °C °C Vre 4.36gN

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PS7516

Application Information

Controller Circuit

The device is based on a current-mode control topology and uses a constant frequency pulse-width modulator to regulate the output voltage. The controller limits the current through the power switch on a pulse by pulse basis. The current sensing circuit is integrated in the device; therefore, no additional components are required. Due to the nature of the boost converter topology used here, the peak switch current is the same as the peak inductor current, which will be limited by the integrated current limiting circuits under normal operating conditions. Synchronous Rectifier

The device integrates an N-channel and a P- channel MOSFET transistor to realize a synchronous rectifier. There is no additional Schottky diode required. Because the device uses a integrated low RDS(ON) PMOS switch for rectification, the power conversion efficiency reaches 93%.

A special circuit is applied to disconnect the load from the input during shutdown of the converter. In conventional synchronous rectifier circuits, the backgate diode of the high-side PMOS is forward biased in shutdown and allows current flowing from the battery to the output. This device, however, uses a special circuit to disconnect the backgate diode of the high-side PMOS and so, disconnects the output circuitry from the source when the regulator is not enabled (EN=low). PSM Mode

The PS7516 is designed for high efficiency over wide output current range. Even at light load, the efficiency stays high because the switching losses of the converter are minimized by effectively reducing the switching frequency. The controller will enter a power saving mode if certain conditions are met. In this mode, the controller only switches on the transistor if the output voltage trips below a set threshold voltage. It ramps up the output voltage with one or several pulses, and goes again into PSM mode once the output voltage exceeds a set threshold voltage.

Device Enable

The device will be shut down when EN is set to GND. In this mode, the regulator stops switching, all internal control circuitry including the low-battery comparator will be switched off, and the load will be disconnected from the input (as described in above synchronous rectifier section). This also means that the output voltage may drop below the input voltage during shutdown.

The device is put into operation when EN is set high. During start-up of the converter, the duty cycle is limited in order to avoid high peak currents drawn from the battery. The limit is set internally by the current limit circuit. Anti-Ringing Switch

The device integrates a circuit which removes the ringing that typically appears on the SW node when the converter enters the discontinuous current mode. In this case, the current through the inductor ramps to zero and the integrated PMOS switch turns off to prevent a reverse current from the output capacitors back to the battery. Due to remaining energy that is stored in parasitic components of the semiconductors and the inductor, a ringing on the SW pin is induced. The integrated anti-ringing switch clamps this voltage internally to VIN; therefore, dampens this ringing. Adjustable Output Voltage

The accuracy of the output voltage is determined by the accuracy of the internal voltage reference, the controller topology, and the accuracy of the external resistor. The reference voltage has an accuracy of ±2%. The controller switches between fixed frequency and PSM mode, depending on load current. The tolerance of the resistors in the feedback divider determines the total system accuracy.

Design Procedure

The PS7516 boost converter family is intended for systems that are powered by a single-cell Ion battery with a typical terminal voltage between 3V to 4.2V.

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PS7516

Application Information (Continued)

(1) Programming the Output Voltage

The output voltage of the PS7516 can be adjusted with an external resistor divider. The typical value of the voltage on the FB pin is 800mV in fixed frequency operation. The maximum allowed value for the output voltage is 5.5V. The current through the resistive divider should be about 100 times greater than the current into the FB pin. The typical current into the FB pin is 0.01µA, and the voltage across R2 is typically 800mV. Based on those two values, the recommended value for R2 is in the range of 800kΩ in order to set the divider current at 1µA. From that, the value of resistor R1, depending on the needed output voltage (VO), can be calculated using Equation 1.

R1 R2

O T F

(3) Capacitor Selection

The major parameter necessary to define the output capacitor is the maximum allowed output voltage ripple of the converter. This ripple is determined by two parameters of the capacitor, the capacitance and the ESR. It is possible to calculate the minimum capacitance needed for the defined ripple, supposing that the ESR is zero, by using Equation 3.

M N

O T O T- N O T

…..(3)

Parameter f is the switching frequency and △V is the maximum allowed ripple.

The total ripple is larger due to the ESR of the output capacitor. This additional component of the ripple can be calculated using Equation 4.

-1 800kΩ

O T800m

-1 …..(1)

ESR O T RESR …..(4)

The total ripple is the sum of the ripple caused by the capacitance and the ripple caused by the ESR of the capacitor. It is possible to improve the design by enlarging the capacitor or using smaller capacitors in parallel to reduce the ESR or by using better capacitors with lower ESR, like ceramics. Tradeoffs must be made between performance and costs of the converter circuit.

A 10µF input capacitor is recommended to improve transient behavior of the regulator. A ceramic or tantalum capacitor with a 100nF in parallel placed close to the IC is recommended.

(2) Inductor Selection

A boost converter normally requires two main passive components for storing energy during the conversion. A boost inductor is required and a storage capacitor at the output. To select the boost inductor, it is recommended to keep the possible peak inductor current below the current limit threshold of the power switch in the chosen configuration.

The second parameter for choosing the inductor is the desired current ripple in the inductor. Normally, it is advisable to work with a ripple of less than 20% of the average inductor current. A smaller ripple reduces the magnetic hysteresis losses in the inductor, as well as output voltage ripple and EMI. But in the same way, regulation time at load changes rises. In addition, a larger inductor increases the total system cost. With those parameters, it is possible to calculate the value for the inductor by using Equation 2.

N O T- N O T

…..(2)

Parameter is the switching requency and Δ L is the ripple current in the inductor, i.e, 20% x IL. With this calculated value and currents, it is possible to choose a suitable inductor. Care must be taken that load transients and losses in the circuit can lead to higher currents. Also, the losses in the inductor caused by magnetic hysteresis losses and copper losses are a major parameter for total circuit efficiency.

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PS7516

Application Information (Continued)

Layout Considerations

As for all switching power supplies, the layout is an important step in the design, especially at high peak currents and high switching frequencies. If the layout is not carefully done, the regulator could show stability problems as well as EMI problems. Therefore, use wide and short traces for the main current path as indicated in bold in Figure 4. The input capacitor, output capacitor and the inductor should be placed as close to the IC as possible. Use a common ground node as shown in Figure 4 to minimize the effects of ground noise. The feedback divider should be placed as close to the IC as possible.

采购找　百盛VINC4C6C1

VOUT65GND4C3C5C2L1GND3LX12R2R1Figure 4. Layout Diagram

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Outline Information

SOT-23-6 Package (Unit: mm)

Carrier Dimensions A A1 A2 B D E E1 e e1 L SYMBOLS UNIT DIMENSION IN MILLIMETER MIN MAX 0.90 0.00 0.90 0.30 2.80 2.60 1.50 0.90 1.80 0.30 1.45 0.15 1.30 0.50 3.00 3.00 1.70 1.00 2.00 0.60 Note：Followed From JEDEC MO-178-C.

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