XRP7665 EXAR | Alldatasheet
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SS yy nn cc hh rr oo nn oo uu ss SS tt ee pp -- DD oo ww nn CC oo nn vv ee rr tt ee rr March 2013 Rev. 2.0. Exar Corporation www.exar.com
48720 Kato Road, Fremont CA 94538, USA
Tel. +1 510 668 - 70 ± Fax. +1 510 668 - 70 GENERAL DESCRIPTION The X RP 7665 is a synchronous current - mode PWM step down (buck) regulator capable of a constant output curent up to Amps. A wide 4.5
0 V to 18V input voltage range allows for
standard 5V and 12V power rails. With a 340kHz constant operating frequency and integrated high and low side 1 0 P
9 P026)(7V
, the XRP 7665 reduces the overall component count and solution footprint. Current - mode control provides fast transient response and cycle - by - cycle curent limit. An adjustable soft - start prevents inrush curent at turn - on, and in shutdown mode the supply curent drops to 0.1µ Built - in output over volta ge (open load) , over temperature , cycle - by - cycle over current and under voltage lockout (UVLO) protections insure safe operations under abnormal operating conditions. The XRP 7665 is a pin and func tion compatible device to MP1484 and a 3A pin to pin upgrade to XRP764 The XRP 7665 is offered in a RoHS compliant, ³JUHHQ´KDORJHQIUHH - pin exposed pad SOIC package
APPLICATIONS
x Distributed Power Architectures x Point of Load Converters x Audio - Video Equipments x Medical & Industrial Equipments
FEATURES
x 4. V to 18V Wide Input Voltage x PWM Current Mode Control 340kHz Constant Operations Up to 93% Eficiency x Adjustable Output Voltage 0.925V to 16V Range 2.0 % Acuracy x Programable Soft - Start and Enable Function x Built - in Thermal , Over Current , UVLO and Output Over Voltage Protections x 5R+6&RPSOLDQW³*UHHQ´+DORJ 8 - Pin Exposed Pad SOIC Package TYPICAL APPLICATION DIAGRAM Fig. 1 : XRP7665 Application Diagram
SS yy nn cc hh rr oo nn oo uu ss SS tt ee pp -- DD oo ww nn CC oo nn vv ee rr tt ee rr © 2013 Exar Corporation Rev. 2.0. ABSOLUTE MAXIMUM RAT INGS These are stres ratings only and functional operation of the device at these ratings or any other above those indicated in the operation sections of the specifications below is not implied. Exposure to absolute maximum rating con ditions for extended periods of time may affect reliability. Supply Voltage V - 0.3V to V Switch Node Voltage V SW V Boost Voltage V BS ... - 0.3 to V SW V Enable Voltage V EN - 0.3 to V IN Al Other Pins - 0.3 to +6 V Junction Temperature 150°C Storage Temperature - 65°C to 150°C Lead Temperature (Soldering, 10 sec) 0°C ESD Rating (HBM - Human Body Model) 2kV ESD Rating (MM - Machine Model) 2 00V Moisture Sensitivity Level (MSL) ... OPERATING RATINGS Input Voltage V 4 . 5 0 V to V Ambient Operating Temperature - 40°C to Maximum Output Current ....
3 A min
7KHUPDO5HVLVWDQFHLJ °C/W ELECTRICAL SPECIFICA TIONS Specifications are for an Operating Ambient Temperature of T A = 25°C only; limits applying over the full Ambient Operating T HPSHUDWXUHUDQJHDUHGHQRWHGE\\D³´0LQLPXPDQG0D[LPXPOLPLWVDUH d through test, design, or statistical correlation. Typical values represent the most likely parametric norm at T A = 25°C, and are provided for reference purposes only. Unles otherwise indicated, V IN = V EN V, V OUT =3.3V Parameter Min. Typ. Max. Units Conditions Shutdown Supply Current 0.1 µA V EN 0.75 V Quiescent Current 1.2 mA V EN
3 V, V
FB =1V Fedback Voltage V FB 0.90 0.925 0.9 V Fedback Overvoltage Threshold 1.1 V Fedback Bias Current - 0.1 0.1 µA V FB =1V Error Amplifier Voltage Gain A EA (Note 1) 400 V/V Error Amplifier Transconductance G EA 800 µ A/V High - Side switch On Resistance R DSON H (Note 2) 1 0 0 I SW =0.2A&0.7A Low - Side switch On Resistance R DSON L (Note 2) 100 I SW - 0.2A& - 0.7A High - Side switch Leakage Current 0.1 µA V IN =18V, V EN =0V, V SW =0V High - Side Switch Current Limit 4.3 5.6 A Low - Side Switch Current Limit 1.4 A From Drain to Source COMP to Current Sense Transconductance G CS 5.2 A/V Oscillator Frequency F OSC1 280 340 400 kHz Short Circuit Oscillator Frequency F OSC kHz Maximum Duty C ycle D MAX V FB =0.85V Minimum Duty Cycle D M IN V FB =1V EN Enable Threshold Voltage 2.2 2.5 2.7 V EN E nable Threshold Voltage Hysteresis (Note 1) 210 mV UVLO Threshold 3.65 4.00 2 5 V V IN Rising
SS yy nn cc hh rr oo nn oo uu ss SS tt ee pp -- DD oo ww nn CC oo nn vv ee rr tt ee rr © 2013 Exar Corporation Rev. 2.0. Parameter Min. Typ. Max. Units Conditions UVLO Hysteresis 0.2 V Soft - start Current µA V SS =0V Soft - start Time (Note 1) 1 5 ms C SS =0.1 µF Thermal Shutdown (Note 1) 160 Thermal Shutdown Hysteresis (Note 1) 2 0 Note 1: Guaranted by design. Note 2: R DSON =(V SW1 - V SW2 )/(I SW1 - I SW2 BLOCK DIAGRAM Fig. 2 : XRP7665 Block Diagram PIN ASSIGNMENT Fig. 3 : XRP7665 Pin Assignment (SOIC - 8 Exposed Pad
SS yy nn cc hh rr oo nn oo uu ss SS tt ee pp -- DD oo ww nn CC oo nn vv ee rr tt ee rr © 2013 Exar Corporation Rev. 2.0. PIN DESCRIPTION Name Pin Number
Description
Bootstrap pin. Connect a 0.01µF or greater bootstrap capacitor between the BS pin and the SW pin. The voltage acros the bootstrap capacitor drives the internal high - side power MOSFET. IN Power input pin. A capacitor should be connected between the IN pin and GND pin to keep the input voltage constant. SW Power switch output pin. This pin is connected to the inductor and the bootstrap capacitor. GND Ground signal pin. FB Fedback pin. An external resistor divider connected to FB programs the output voltage. If the fedback pin exceeds 1.1V the over - voltage protection will trigger. If the feedback voltage drops below 0.3V the o scillator frequency is lowered to achieve short - circuit protection. COMP Compensation pin. This is the output of transconductance error amplifier and the input to the current comparator. It is used to compensate the control loop. Connect an RC network form this pin to GND. EN Control input pin. Forcing this pin above 2.7V enables the IC. Forcing this pin below 0.75 V shuts down the ,&3XOOXSWR9,1ZLWKNƻIRUDXWRPDWLFVWDUWXS SS Soft - start control input pin. Connect a capacitor from S to GND to set the soft - start period. A 0.1µF capaci tor sets the soft start period to 1 5 ms. To disable the soft - start feature, leave S unconnected. EP Exposed Pad Connect to GND through PCB
ORDERING INFORMATION
- F - &7 A & XRP766 5 I YYWWF X SOIC - 8 (EP) 2.5 K/Tape & Rel RoHS Compliant Halogen Fre XRP 766
5 EVB
5 Evaluation Board
³<<´ <HDU ± ³::´ :RUN:HHN ± ³;´ /RW1XPEHU ; when applicable.
SS yy nn cc hh rr oo nn oo uu ss SS tt ee pp -- DD oo ww nn CC oo nn vv ee rr tt ee rr © 2013 Exar Corporation Rev. 2.0. TYPICAL PERFORMANCE CHARACTERISTICS Al data taken at V IN = V OUT =3.3V, T J = T A = 25°C, unles otherwise specified - Schematic and BOM from Application Information section of this datashet. Fig. 4 : Efficiency versus output current Fig. 5 : R DSONH versus case temperature Fig. 6 : R DSON L versus case temperature Fig. 7 : Fedback voltage versus case temperature Fig. 8 : Quiescent current versus case temperature Fig. 9 : Output voltage versus output current
SS yy nn cc hh rr oo nn oo uu ss SS tt ee pp -- DD oo ww nn CC oo nn vv ee rr tt ee rr © 2013 Exar Corporation Rev. 2.0. Fig. : Output voltage ripple, I OUT 3 A Fig. : Load transient ( I OUT 1 .5 A to 3 A) Fig. : Enable turn on CC mode, V IN =12V, V OUT EN =3.3, I OUT =3A Fig. : Enable turn off CC mode , V IN =12V, V OUT EN =3.3, I OUT =3A Fig. : Short - circuit protection Fig. : Short - circuit recovery
SS yy nn cc hh rr oo nn oo uu ss SS tt ee pp -- DD oo ww nn CC oo nn vv ee rr tt ee rr © 2013 Exar Corporation Rev. 2.0. THEORY OF OPERATION F UNCTIONAL D ESCRIPTION The XRP 7665 is a synchronous, current - mode, step - down regulator. It regulates input voltages from 4 .5V to 18V and supplies up to
3 A of
. The XRP 7665 uses curent - mode control to regulate the output voltage. The output voltage is measured at FB through a resistive voltage divider and input to a transconductance error amplifier. The high - side switch curent is compared to the output of the error amplifi er to control the output voltage. The regulator utilizes internal N - channel MOSFETs to step down the input voltage. A bootstrapping capacitor connected between BS and SW acts as a supply for high - side MOSFET. This capacitor is charge d from the internal 5V supply when SW node is low. The XRP 7665 has several powerful protection fe atures including OCP, OVP, OTP, UVLO and output short - circuit PROGRAMMABLE SOFT - START The soft - start time is fully programmable via CSS capacitor , placed between the S and GND pin The CSS is charged by a 6µA constant - current source, generating a ramp signal fed into non - inverting input of the error amplifier. This ramp regulates the voltage on comp pin during the regulator startup, thus realizing soft - start. Cal culate the required CSS from: ܥܵܵ ൌݐݏݏ ൈɊܣ ܸி Where: ts is the required soft - start time V FB is the feedback voltage (0.925V nominal) ENABLE FUNCTION The XRP7665 is enabled by raising the voltage on the EN pin above 2.5V nominally. Connect the EN pin to the VIN via DNƻUHVLVWRUIRU automatic start - up. Shutdown is achieved by pulling the EN pin voltage below 1.1V nominally. OVERCURRENT PROTECTI ON OCP The OCP protects against acidental increase in load curent that can cause the regulator to fail. The curent of internal switch M1 is monitored. If this curent reaches 5.6 A then M1 is turned of until next switch ing cycle. SHORT - CIRCUIT PROTECTION If th ere is short - circuit acros the output , the feedback voltage V FB will droop. If V FB drops below 0.3V the XRP 7665 will detect a short circuit condition and reduce the switching frequency to 90kHz for system protection. The regulator will restart once the short - circuit has been removed. OVERVOLTAGE PROTECTI ON OVP The XRP 7665 has internal OVP. When V OUT exceeds the OVP threshold (when V FB e xceeds 1.1V) the power switching will be turned of The XRP 7665 will restart when o vervoltage condition is removed OVE R - TEMPERATURE PROTECTI ON OTP If the junction temperature exceeds 160 ° C the OTP circuit is triggered, turning of the internal control circuit and switched M1 and M2. When junction temperature drops below 1 4 0 ° C the XRP 7665 will restart. APPLICATION INFORM ATION SETING THE OUTPUT V OLTAGE Use an external resistor divider to set the output voltage. Program the output voltage from: ͲǤͻʹͷ ܸെͳ൰ Where: R1 is the resistor between V OUT and FB R2 is the resistor between FB and GND QRPLQDOO\\N 0.925V is the nominal feedback voltage
SS yy nn cc hh rr oo nn oo uu ss SS tt ee pp -- DD oo ww nn CC oo nn vv ee rr tt ee rr © 2013 Exar Corporation Rev. 2.0. OUTPUT INDUCTOR Select the output inductor for inductance L, DC curent rating I DC and saturation curent rating I SAT . I DC should be larger than regulator output curent. I SAT , as a rule of thumb, should be 50% high er than the regulator output curent. Since the regulator is rated at
3 A then
3 A and I SAT 4.5 Calculate the inductance from: ܸை் ൈ݂ ௦ൈܸூே Where: L is peak - to - peak inductor current ripple nominally set to 30% - 40% of I OUT f S is nominal switching frequency (340kHz) As an example , inductor values for several comon output voltages are shown in table s 1 and 2 . Note that example inductors shown in table s 1 and 2 are Wurth shielded inductors. If the target application is not sensitive to EMI then unshielded inductors may be used. VOUT(V) L ( p - p ) (A) µ H) Inductor Example 5.0 0.9 744314101 3.3 0.7 744314101 2.5 0.6 744314101 1.8 0.6 7.6 744314 760 1.5 0.5 7.6 744314 760 1.2 0.6 4.9 744314 490 Table 1 : Suggested inductor values for V IN =12V and I OUT 3 A VOUT(V) L (p - p) (A) L(µH) Inductor Example 3.3 0.7 4.9 744314 490 2.5 0.8 4.9 744314 490 1.8 0.7 4.9 744314 490 1.5 0.6 4.9 744314 490 1.2 0.5 4.9 744314 490 Table 2 : Suggested inductor values for V IN =5V and I OUT 3 A OUTPUT CAPACITOR C OUT Select the output capacitor for voltage rating, capacitance C OUT and Equivalent Series Resistance ESR . The voltage rating, as a rule of thumb, should be at least twice the output voltage. When calculating the required capacitance, usually the overriding requirement is curent load - step transient. If the unloading transient (i.e., when load transitions from a high to a low curent ) is met, then usually the loading transient (when load transitions from a low to a high cu rrent is met as well. Therefore c alculate the C OUT based on the unloading transient requirement from: ܫ ு ଶെܫ ௪ ଶ ሻ ଶቇ Where: L is the inductance calculated in the preceding step I High is the value of load - step prior to unloading. This is nominally set equal to regulator curent rating ( 3 A). I Low is the value of load - step after unloading. This is nominally set equal to 50% of regulator curent rating ( 1 .5 A). V transient i s the maximum permisible voltage transient corresponding to the load step mentioned above. V transient is typically specified from 3% to 5% of V OUT ESR of the capacitor ha s to be selected such that the output voltage ripple requirement OUT , nominally 1% of V OUT , is met. Voltage ripple OUT is mainly composed of t wo components : the resistive ripple due to ESR and capacitive ripple due to C OUT charge transfer. For applications requiring low voltage ripple , c eramic capacitors are recomended because of their low ESR which is typically in the range of P. Therefore OUT is mainly capacitive. For ceramic capacitors c alculate the OUT from: Where: L is from table 1 or 2 C OUT is the value calculated above f s is nominal switching freq uency (340kHz)
Table 3. Optional Schotky diode input voltage is 5V or the output is 5V or 3.3V.
- The external bootstrap diode is also
1 N 4 1 4 8
SS yy nn cc hh rr oo nn oo uu ss SS tt ee pp -- DD oo ww nn CC oo nn vv ee rr tt ee rr © 2013 Exar Corporation / 12 Rev. 2.0. ͳ w here R load is the output load resistance The uncompensated regulator has a constant gain up to its pole frequency, beyond which the gain decreases at - 20dB/decade. The zero arising from the output capacitor ¶s ESR is inconsequential if ceramic C OUT is used. This sim plifies the compensation. The RC and C which are placed between the output of XRP 7665 (UURU $PSOLILHU DQG constitute a zero. The frequency of this compensating zero is given by: ͳ ʹߨൈܴܥൈܥܥ For the typical aplication circuit, RC= 6 .8 and C= 9 nF provide a satisfactory compensation . Please contact EXAR if you need asistance with the compensation of your particular circuit. TYPICAL APPLICATIONS Fig. : XRP 7665 Typical Application Diagram - 12V to 3.3V Conversion
SS yy nn cc hh rr oo nn oo uu ss SS tt ee pp -- DD oo ww nn CC oo nn vv ee rr tt ee rr © 2013 Exar Corporation / 12 Rev. 2.0. PACKAGE SPECIFICATIO N 8 - P IN SOIC E XPOSED P AD Unit: m (inch) Eject hole, oriented hole and mold mark are optional.
SS yy nn cc hh rr oo nn oo uu ss SS tt ee pp -- DD oo ww nn CC oo nn vv ee rr tt ee rr © 2013 Exar Corporation / 12 Rev. 2.0.
REVISION HISTORY
1.0.0 02/14/2011 Initial release of datashet 1.1.0 10/13/2011 Added Moisture Sensitivity Level (MSL) information 2.0.0 02/12/2013 Reformat of datashet Changed min operating input voltage from 4.75V to 4.5V Updated Electrical Specifications parameter (quiescent current, fedback voltage, high and low side switch on - resistance, oscillator frequency, EN shutdown threshold voltage and hysteresis, EN lockout threshold voltage and hysteresis, UVLO threshold and hy steresis, soft - start time) Updated figure 2: XRP7665 block diagram Updated Pin Description, EN pin description Updated all Typical Performance Characteristics curves 2.0.1 3/29/2013 Updated Enable pin description Deleted Electrical Specification para meter s (shutdown supply current, EN shutdown threshold voltage and hysteresis, EN lockout threshold voltage and hysteresis) Added Electrical Specification para meter s (EN enable t hreshold voltage and hysteresis paragraph to the theory of operation section. FOR FURTHER ASSISTAN CE Email: customersupport@exar.com powertechsupport@exar.com Exar Technical Documentation: http://w.exar.com/TechDoc/default.aspx? E XAR C ORPORATION H EADQUARTERS AND S ALES O FFICES
48720 Kato Road
Fremont, CA 94538 ± USA Tel.: +1 (510) 68 - 7000 Fax: +1 (510) 68 - 7030 w.exar.com NOTICE EXAR Corporation reserves the right to make changes to the products contained in this publication in order to improve design, performance or reliability. EXAR Corporation asumes no responsibility for the use of any circuits described herein, conveys no license under any patent or other right, and makes no rep resentation that the circuits are fre of patent infringement. Charts and schedules contained here in are only for illustration purposes and may vary depending upon a XVHU¶VVSHFLILFDSSOLFDWLRQ:KLOHWKHLQIRUPDWLRQLQWKLVSXEOLFDWLR checked; no responsibility, however, is asumed for inacuracies. EXAR Corporation does not recomend the use of any of its products in life support applications where the failure or malfunction of the product can reasonably be expected to cause failure o f the life support system or to significantly affect its safety or effectivenes. Products are not authorized for use in such applications unles EXAR Corporation receives, in writing, asurances to its satisfaction that: (a) the risk of injury or damage h as ben minimized; (b) the user asumes all such risks; (c) potential liability of EXAR Corporation is adequately protected under the circumstances. Reproduction, in part or whole, without the prior written consent of EXAR Corporation is prohibited.