Richtek RT7285C Manual Download

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RT7285C

DS7285C-03 July 2014

www.richtek.com

Outline Dimension

SOT-23-6 Surface Mount Package

Dimensions In Millimeters

Dimensions In Inches

Symbol

Min Max Min Max

A 0.889 1.295 0.031 0.051

0.000

0.152

0.000

0.006

1.397

1.803

0.055

0.071

0.250

0.560

0.010

0.022

2.591

2.997

0.102

0.118

2.692

3.099

0.106

0.122

0.838

1.041

0.033

0.041

0.080

0.254

0.003

0.010

0.300

0.610

0.012

0.024

Summary of Contents for RT7285C

Page 1: ...acitors The output voltage can be adjusted between 0 6V and 8V Features 4 3V to 18V Input Voltage Range 1 5A Output Current Advanced Constant On Time Control Fast Transient Response Support All Ceramic Capacitors Up to 95 Efficiency 500kHz Switching Frequency Adjustable Output Voltage from 0 6V to 8V Cycle by Cycle Current Limit Input Under Voltage Lockout Hiccup Mode Under Voltage Protection Ther...

Page 2: ...on Block Diagram Operation The RT7285C is a synchronous step down converter with advanced constant on time control mode Using theACOT control mode can reduce the output capacitance and fast transient response It can minimize the component size without additional external compensation network Current Protection The inductor current is monitored via the internal switches cycle by cycle Once the outp...

Page 3: ... Low VEN_L 0 4 VIN Under Voltage Lockout Threshold VUVLO VIN Rising 3 55 3 9 4 25 V VIN Under Voltage Lockout Threshold Hysteresis 340 mV Electrical Characteristics VIN 12V TA 25 C unless otherwise specified Absolute Maximum Ratings Note 1 VINtoGND 0 3V to 20V SW to GND 0 3V to VIN 0 3V 10ns 5V to 25V BOOT toGND VSW 0 3V to VSW 6V Other Pins 0 3V to 6V Power Dissipation PD TA 25 C SOT 23 6 TSOT 23...

Page 4: ... maximum rating conditions may affect device reliability Note 2 θJA is measured at TA 25 C on a high effective thermal conductivity four layer test board per JEDEC 51 7 The case position of θJC is on the top of the package Note 3 Devices are ESD sensitive Handling precaution is recommended Note 4 The device is not guaranteed to function outside its operating conditions Parameter Symbol Test Condit...

Page 5: ...htek Technology Corporation Typical Application Circuit VOUT V R1 kΩ R2 kΩ L μH COUT μF CFF pF 5 110 15 10 22 39 3 3 115 25 5 6 8 22 33 2 5 25 5 8 06 4 7 22 NC 1 2 10 10 3 6 22 NC Table 1 Suggested Component Values VIN EN GND BOOT FB SW 4 3 5 6 1 L 3 6µH 100nF 22µF R1 10k R2 10k VOUT 1 2V 10µF VIN 4 3V to 18V RT7285C CBOOT CIN COUT Enable 2 CFF ...

Page 6: ...V Switcing Frequency kHz 1 VOUT 1 2V IOUT 0A Output Voltage vs Load Current 1 190 1 194 1 198 1 202 1 206 1 210 1 214 1 218 1 222 1 226 1 230 0 0 3 0 6 0 9 1 2 1 5 Load Current A Output Voltage V VIN 4 5V to 18V VOUT 1 2V VIN 18V VIN 12V VIN 9V VIN 5V VIN 4 5V Reference vs Temperature 0 590 0 595 0 600 0 605 0 610 50 25 0 25 50 75 100 125 Temperature C Reference Voltage V IOUT 0A VIN 12V Efficienc...

Page 7: ...V Div Time 100μs Div Load Transient Response VOUT 20mV Div IOUT 1A Div VIN 12V VOUT 1 2V IOUT 0 75A to 1 5A Switching Frequency vs Temperature 450 470 490 510 530 550 570 590 610 630 650 50 25 0 25 50 75 100 125 Temperature C Switching Frequency kHz 1 VOUT 1 2V VIN 6V VIN 12V VIN 18V VIN 4 5V Current Limit vs Temperature 1 0 1 2 1 4 1 6 1 8 2 0 2 2 2 4 2 6 2 8 3 0 50 25 0 25 50 75 100 125 Temperat...

Page 8: ...me 2 5ms Div Power Off from VIN VIN 12V VOUT 1 2V IOUT 1 5A VOUT 1V Div ISW 1A Div Time 5ms Div Power Off from EN VIN 12V VOUT 1 2V IOUT 1 5A VOUT 1V Div VEN 2V Div ISW 1A Div VSW 10V Div Time 2 5ms Div Power On from VIN VIN 12V VOUT 1 2V IOUT 1 5A VOUT 1V Div VIN 10V Div ISW 1A Div VSW 10V Div Time 2 5ms Div Power On from EN VIN 12V VOUT 1 2V IOUT 1 5A VOUT 1V Div VEN 2V Div ISW 1A Div VSW 10V Di...

Page 9: ...d an input voltage of 12V using an inductor ripple of 0 6A 40 the calculated inductance value is 1 2 12 1 2 L 3 6μH 12 500kHz 0 6 The ripple current was selected at 0 6A and as long as we use the calculated 3 6μH inductance that should be the actual ripple current amount The ripple current and required peak current as below L 1 2 12 1 2 I 0 6A 12 500kHz 3 6μH L PEAK 0 6 and I 1 5A 1 8A 2 Inductor ...

Page 10: ...th 1 x 22μF output capacitance each with about 5mΩ ESR including PCB trace resistance the output voltage ripple components are RIPPLE ESR V 0 46A 5m 2 3mV RIPPLE C 0 46A V 5 227mV 8 22μF 500kHz RIPPLE V 2 3mV 5 227mV 7 527mV But some modern digital loads can exhibit nearly instantaneous load changes and the following section shows how to calculate the worst case voltage swings in response to very ...

Page 11: ...ough a 100kΩ resistor Its large hysteresis band makes EN useful for simple delay and timing circuits EN can be externally pulled to VIN by adding a resistor capacitor delay REN and CEN in Figure 2 Calculate the delay time using EN s internal threshold where switching operation begins 1 4V typical An external MOSFET can be added to implement digital control of EN when no system voltage above 2V is ...

Page 12: ...l power dissipation The switch OUT R2 V 0 6 R1 0 6 Place the FB resistors within 5mm of the FB pin Choose R2 between 10kΩ and 100kΩ to minimize power consumption without excessive noise pick up and calculate R1 as follows SW BOOT 5V 0 1µF RT7285C Over Temperature Protection The RT7285C features an Over Temperature Protection OTP circuitry to prevent from overheating due to excessive power dissipat...

Page 13: ...n depends on the operating ambient temperature for fixed TJ MAX and thermal resistance θJA The derating curve in Figure 7 allows the designer to see the effect of rising ambient temperature on the maximum power dissipation Figure 7 Derating Curve of Maximum PowerDissipation Layout Considerations For best performance of the RT7285C the following layout guidelines must be strictly followed Input cap...

Page 14: ...n Outline Dimension A A1 e b B D C H L SOT 23 6 Surface Mount Package Dimensions In Millimeters Dimensions In Inches Symbol Min Max Min Max A 0 889 1 295 0 031 0 051 A1 0 000 0 152 0 000 0 006 B 1 397 1 803 0 055 0 071 b 0 250 0 560 0 010 0 022 C 2 591 2 997 0 102 0 118 D 2 692 3 099 0 106 0 122 e 0 838 1 041 0 033 0 041 H 0 080 0 254 0 003 0 010 L 0 300 0 610 0 012 0 024 ...

Page 15: ... embodied in a Richtek product Information furnished by Richtek is believed to be accurate and reliable However no responsibility is assumed by Richtek or its subsidiaries for its use nor for any infringements of patents or other rights of third parties which may result from its use No license is granted by implication or otherwise under any patent or patent rights of Richtek or its subsidiaries T...

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