LV5768M

Ordering number : ENA1988 Bi-CMOS LSI LV5768M Overview Functions 1-channel Step-down Switching Regulator The LV5768M is a 1-channel step-down switching regulator. • 1 channel step-down switching regulator controller. • Frequency decrease function at pendent. • Load-independent soft start circuit. • ON/OFF function. • Built-in pulse-by-pulse OCP circuit. It is detected by using ON resistance of an external MOS. • Synchronous rectification • Current mode control Specifications Absolute Maximum Ratings at Ta = 25°C Parameter Supply voltage VIN, SW HDRV, CBOOT Allowable pin voltage LDRV Between CBOOT to SW Between CBOOT to HDRV EN, ILIM Between VIN to ILIM VDD SS, FB, COMP,RT Allowable Power dissipation Operating temperature Storage temperature Pd max Topr Tstg Mounted on a specified board. * VIN+0.3 1.0 6.0 VDD+0.3 0.9 -40 to +85 -55 to +150 V V V V W °C °C Symbol VIN max Conditions Ratings 45 45 52 6.0 6.0 Unit V V V V V * Specified board : 114.3mm × 76.1mm × 1.6mm, glass epoxy board. Any and all SANYO Semiconductor Co.,Ltd. products described or contained herein are, with regard to "standard application", intended for the use as general electronics equipment. The products mentioned herein shall not be intended for use for any "special application" (medical equipment whose purpose is to sustain life, aerospace instrument, nuclear control device, burning appliances, transportation machine, traffic signal system, safety equipment etc.) that shall require extremely high level of reliability and can directly threaten human lives in case of failure or malfunction of the product or may cause harm to human bodies, nor shall they grant any guarantee thereof. If you should intend to use our products for new introduction or other application different from current conditions on the usage of automotive device, communication device, office equipment, industrial equipment etc. , please consult with us about usage condition (temperature, operation time etc.) prior to the intended use. If there is no consultation or inquiry before the intended use, our customer shall be solely responsible for the use. Specifications of any and all SANYO Semiconductor Co.,Ltd. products described or contained herein stipulate the performance, characteristics, and functions of the described products in the independent state, and are not guarantees of the performance, characteristics, and functions of the described products as mounted in the customer's products or equipment. To verify symptoms and states that cannot be evaluated in an independent device, the customer should always evaluate and test devices mounted in the customer ' s products or equipment. D0711 SY 20091029-S00002 No.A1988-1/15 LV5768M Recommended Operating Range at Ta = 25°C Parameter Supply voltage range Error amplifier input voltage Oscillatory frequency Symbol VIN VFB FOSC Conditions Ratings 8.5 to 42 0 to 1.6 80 to 500 Unit V V kHz Electrical Characteristics at Ta = 25°C, VIN = 12V Parameter Reference voltage block Internal reference voltage 5V power supply Triangular waveform oscillator block Oscillation frequency Frequency variation Oscillation frequency fold back detection voltage Oscillation frequency after fold back ON/OFF circuit block IC start-up voltage IC off voltage Soft start circuit block Soft start source current Soft start sink current UVLO circuit block UVLO lock release voltage UVLO hysteresis Error amplifier Input bias current Error amplifier gain Sink output current Source output current Current detection amplifier gain over current limiter circuit block Reference current Over current detection comparator offset voltage Over current detection comparator common mode input range PWM comparator Input threshold voltage (FOSC=125kHz) Maximum ON duty Output block Output stage ON resistance (the upper side) Output stage ON resistance (the under side) Output stage ON current (the upper side) Output stage ON current (the under side) The whole device Standby current Mean consumption current ICCS ICCA EN < 1V EN > 3.5V 3 10 μA mA Continued on next page. IONL 240 mA IONH 240 mA RONL 5 Ω RONH 5 Ω Vt max Vt0 DMAX Duty cycle = DMAX Duty cycle = 0% 0.9 0.4 85 1.0 0.5 90 1.1 0.6 95 V V % VIN-0.45 VIN V ILIM1 VLIM OFS -10% -5 18.5 +10% +5 μA mV IEA IN GEA IEA OSK IEA OSC GISNS FB = 1.0V FB = 0V 1000 1400 -100 100 1.5 100 1800 nA μA/V μA μA VUVLO VUVLO H 8 0.7 V V ISS SC ISS SK EN > 3.5V EN < 1V, VDD = 5V 4 5 2 6 μA mA VEN on VEN off 2.5 1.0 3.0 1.2 3.5 1.4 V V FOSC FB 1/3FOSC kHz FOSC FOSC DV VOSC FB RT=220kΩ VIN = 8.5 to 42V FB voltage detection after SS ends 110 125 1 0.1 140 kHz % V Vref VDD Including offset of E/A IOUT = 0 to 5mA 0.654 4.7 0.67 5.2 0.686 5.7 V V Symbol Conditions Ratings min typ max Unit No.A1988-2/15 LV5768M Continued from preceding page. Parameter Security function Protection function operating temperature at high temperature Protection function hysteresis at high temperature TSD hys * Design certification 30 °C TSD on * Design certification 170 °C Symbol Conditions Ratings min typ max Unit Package Dimensions unit : mm (typ) 3111A 1.0 Pd max -- Ta 8.0 14 8 Allowable power dissipation, Pd max -- W 0.9 0.8 4.4 6.4 0.63 0.6 0.47 0.4 (1.0) 1.0 0.35 0.1 (1.5) 1.7MAX 1 7 0.15 0.2 SANYO : MFP14S(225mil) Specified board : 114.3 × 76.1 × 1.6mm3 glass epoxy board. 0 --40 --20 0 20 40 60 8085 100 Ambient temperature, Ta -- C Pin Assignment FB 1 COMP 2 EN 3 RT 4 SW 5 CBOOT 6 HDRV 7 Top view 14 SS 13 ILIM 12 VIN LV5768M 11 GND 10 VDD 9 NC 8 LDRV No.A1988-3/15 LV5768M Block Diagram VIN 12 5V REGULATOR 5V REFERENCE VOLTAGE VDD UVLO TSD VIN UVLO ILIM 13 + OCP Comp SQ R VIN + Current Amp SAW WAVE OSCILLATOR fosc forcec 1/3 6 CBOOT 7 HDRV DMAX = 90% 1.0V 0.5V 5 SW + PWM Comp CONTROL Logic 5V 10 VDD 8 LDRV 1.1V SD + - SD SQ R SS 14 FB 1 COMP 2 0.67V + + - + SS Amp Err Amp 11 GND 0.1V shut down(SD) 0.1V 1.2V RT 4 + - + - FFOLD Amp 3 EN Pin Function Pin No. 1 Pin name FB Description Error amplifier reverse input pin. By operating the converter, the voltage of this pin becomes 0.67V. The voltage in which the output voltage is divided by an external resistance is applied to this pin. Moreover, when this pin voltage becomes 0.1V or less after a soft start ends, the oscillatory frequency becomes 1/3. 2 3 4 5 6 7 8 9 10 11 12 13 COMP EN RT SW CBOOT HDRV LDRV N.C. VDD GND VIN ILIM Error amplifier output pin. Connect a phase compensation circuit between this pin and GND. ON/OFF pin. Oscillation frequency setting pin. Resistance is connected with this pin between GND. Pin to connect with switching node. Upper part NchMOSFET external a source is connected with lower side NchMOSFET external a drain. Bootstrap capacity connection pin. This pin becomes a GATE drive power supply of an external NchMOSFET. Connect a bypath capacitor between CBOOT and SW. An external the upper MOSFET gate drive pin. An external the lower MOSFET gate drive pin. No connection Power supply pin for an external the lower MOS-FET gate drive. Ground pin. Each reference voltage is based on the voltage of the ground pin. Power supply pin. This pin is monitored by UVLO function. When the voltage of this pin becomes 8V or more by UVLO function, The IC starts and the soft start function operates. Reference current pin for current detection. The sink current of about 18.5μA flows to this pin. When a resistance is connected between this pin and VIN outside and the voltage applied to the SW pin is lower than the voltage of the terminal side of the resistance, the upper NchMOSFET is off by operating the current limiter comparator. This operation is reset with respect to each PWM pulse. 14 SS Pin to connect a capacitor for soft start. A capacitor for soft start is charged by using the voltage of about 5μA. This pin ends the soft start period by using the voltage of about 1.1V and the frequency fold back function becomes active. No.A1988-4/15 LV5768M I/O pin equivalent circuit chart Pin No. FB, SS VDD 10 Equivalent Circuit FB 1 SS 14 GND 11 Standard voltage 0.67V 0.1V 1.3V 1.1V COMP VDD 10 COMP 2 1.6V GND 11 EN VIN 12 EN 3 GND 11 RT VDD 10 RT 4 GND 11 Continued on next page. No.A1988-5/15 LV5768M Continued from preceding page. Pin No. SW, CBOOT, HDRV VIN 12 CBOOT 6 Equivalent Circuit HDRV 7 SW 5 GND 11 LDRV VDD 10 LDRV 9 GND 11 VDD VIN 12 VDD 10 GND 11 ILIM VIN 12 ILIM 13 GND 11 No.A1988-6/15 LV5768M Boot sequence, UVLO, and TSD operation UVLO 8V VIN VDD=90% VDD 1.1V 7.3V VREF 0.67V SS Permisson of Foldback VOUT HDRV-SW LDRV 170 C 140 C TSD Sequence of overcurrent protection VIN ILIM SW Driving usually Overcurrent protection oparation Overcurrent protection oparation(Foldback oparation) Soft start start section Driving usually IOUT SS FB 0.67V FB=0.1V No.A1988-7/15 LV5768M Sample Application Circuit VIN=24V, VOUT=12V, IOUT=7A, Fosc=100kHz VIN=24V C7=1000pF C6=1000pF VIN ILIM CBOOT HDRV EN SW SS COMP RT C12=47pF GND LDRV FB VDD Cx=1nF Q2=ATP206 (SANYO) + D1=DSE010 D2=CMS15 (60V,3A) + Q1=ATP201 (SANYO) OUT=12V GND PS No.A1988-8/15 LV5768M • Part selection and set 1) Output voltage set Output voltage (VOUT) is shown the equation (1). R4 22kΩ VOUT = (1 + R3 )×VREF = (1 + 1.3kΩ )×0.67 (typ) [V] (1) Ex) To set output voltage of 12V, set resistors as follows: R3=1.3kΩ and R4=22kΩ. 2) Soft start set Soft start capacitor (C5) is obtained by the equation (2). C5 = ISS×TSS 5µ×TSS VREF = 0.67V [µF] (2) ISS: Charge current value, TSS: soft start time Ex) To set soft start time of 15ms (approx.), set C5=0.1µF. 3) Overcurrent protector set Overcurrent limit setting resistor (R5) is obtained by the equation (3). R5 = Rdson×IL max Rdson×IL max = 18.5µ IIlim [Ω] (3) IIlim: ILIM current value, ILmax: the maximum value of coil current, Rdson: Ron between drain and source of Q1 (upper Nch MOS FET). Ron of ATP201 ≈ 23mΩ (when VGS=4.5V at 25°C) Ex) To set current limit operation point to 11.3A (load current) where coil peak current value is 12A (approx.), set R5 = 15kΩ. Set an optimum resistor taking variation of ON resistor into consideration due to temperature change and make sure to confirm it with the user's specific board. For C6, connect a capacitor of 1000pF to filter unwanted noise for the proper operation of current limiting. ON resistor of FET * Rdson of FET has its own temperature coefficient and the resistor becomes higher in proportion to the temperature. * To set Rdson value within the range of operating temperature, it is advisable that the user confirm the data sheet by the FET supplier. 4) How to set oscillation frequency Oscillation frequency Fosc is adjustable by RT resistor as shown in the correlation chart as follows: SW frequency setting range: 80kHz to 500kHz Frequency, FOSC - kHz 500 450 400 350 300 250 200 150 100 50 0 0 50 100 150 FOSC -- RT 200 250 300 350 400 450 500 Resistance, RT - kΩ 5) Boot strap capacitor set For boot strap capacitor C2, use capacitor 100 times larger than Ciss of power MOSFET. PS No.A1988-9/15 LV5768M 6) Phase compensation set Since LV5768M adopts current mode control, low ESR capacitor and solid polymer capacitor such as OS capacitor can be used as output capacitor with simple phase compensation. *Frequency characteristics Frequency characteristics of LV5768M consist of the following transfer functions. (1) Output resistor bleeder ; HR (2) Voltage gain of error amplifier ; GVEA Current gain (Trans conductance) ; GMEA (3) Impedance of external phase compensation part ; ZC (4) Current sense loop gain ; GCS (5) Output smoothing impedance ; ZO SLOPE OSC CLK GVER ΔVI VREF 1/GCS PWM comparator + Current sense loop VIN L SW CO RL R2 R1 VO + ΔVO Error amplifier COMP CC RC FB Control logic GMER HR Fig. Current control loop of LV5768M Closed loop gain is obtained by the equation (5) G = HR × GMEA × ZC × GCS × ZO RL VREF 1 R5 = V × GMER × (RC + C ) × GCS × 1+ C R O SC SOL (4) From the equation (4), the frequency characteristics of closed loop gain is given by pole fp1 which consists of output capacitor Co and output load resistor RL, zero point fz which is given by external resistor Rc and capacitor Cc of phase compensation pin COMP and pole fp2 which is given by output impedance ZO and external phase compensation capacitor Cc of error amplifier. fp1, fz, fp2 are given by the equation (5), (6) and (7). 1 1 1 fp1 = 2πC R (5), fz = 2πC R (6), fp2 = 2π × ZEA × CC OL CL *Calculation of phase compensation external constants RC and CC In general, the frequency where closed loop gain becomes 1 (zero cross frequency fzc) should be 1/10 of the switching frequency (or 1/5 at the highest) to stabilize the operation of switching regulator. Ex) When switching frequency of LV5768M is 100kHz: fzc = 100kHz 10 ≈ 10kHz (8) (7) Since the closed loop gain becomes 1 with this frequency, the equation (7) = 1 RL 1 Vref VO × GMEA × (RC + SCC ) × GCS1+SCORL = 1 In reality for zero cross frequency, in the impedance of phase compensation capacity, since capacity element becomes lower enough than the resistor element RC: RC » (9) 1 CC S (10) 1 CC S PS No.A1988-10/15 LV5768M The equation (9) becomes RL Vref × GMEA × RC × =1 VO 1+2π × fZC × CO × RL (11) From the equation, phase compensation external resistor RC is obtained by the following formula. However, GCS=0.67/Rdson=29A/V, GMEA=1400µA/V. Given that output is 12V and load resistor is 1.7Ω (7A load): VO 1+2π × fZC × CO × RL 1 1 ∴ RC = Vref × G ×G × RL MEA CS 1 1 1+2 × 3.14 × 10k × 1410µ × 1.7 12 = 0.67 × 1400µA/V × 29A/V × 1.7 ≈ 39kΩ (13) (12) This is the external resistor value RC obtained from this calculation (the calculation reveals that the last block where load resistor RL is inserted is 1 « 2π × fZC × CO × RL. Therefore, there is no need for depending RL.). When point zero fZ (6) and pole fp1 (5) are the same values, they cancel out each other. Hence, there is only one pole frequency for the phase characteristics of closed loop gain. In other words, you can obtain characteristics in which waveform is stable because the gain frequency lowers at -20dB/DEC and phase only rotates by -90 degree. Since (6) = (5) fZ = fp1 (14) 1 1 = 2πCORC 2πCORL RL × CO 1.7 × 1410µ ∴ CC = R = = 0.062µF 39k C The external constant between phase compensator pin COMP and GND is obtained as such using ideal equations. In reality, stable phase constant should be defined based on testing under the entire temperature, load and input voltage range. On the other hand, such ideal value is used as starting point for the assessment. In the deliverable evaluation board, the above constants are used as initial value. CC and RC are defined according to conditions of transient response. If the influence of noise is significant, it is advisable to increase constant than the CC value. 7) Input capacitor selection When switching of the IC occurs, ripple current flows into the input-side capacitor of DC-DC converter. Like input current, the more the output current flows, the more the ripple current into input side capacitor flows. Also, the lower the input voltage is, the more the duty expands. As a result, the ripple current flows more. Allow higher ripple current than the result of the equation. The capacitor of input side should be connected adjacent to the power IC and minimize the inductance from the pattern layout. Execution value is obtained by the equation (15). Irip_in = D(1 − D) × IOUT [Arms] (15) D represents duty cycle defined by VOUT/VIN. 8) Output capacitor selection If ceramic capacitor is used to output, output ripple voltage is obtained as follows since the capacitance of ESR is small. Vrip = VOUT VOUT 2 × (1VIN ) [V] 8 × L × CO × fOSC (16) Also if electrolytic capacitor is used to output, output ripple voltage is affected by ESR since the capacitance of ESR is large. In this case, output ripple voltage is obtained by the following equation. Vrip = VIN - VOUT VOUT × RC × L fOSC × VIN [V] (17) Since the allowable ripple current of electrolytic capacitor is lower compared to that of ceramic capacitor, the allowable ripple current value must not be exceeded. Execution value is obtained by the following equation. PS No.A1988-11/15 LV5768M Irip_out = 1 2 3 × VOUT (VIN - VOUT) L × fOSC × VIN [Arms] (18) It is advisable to use ceramic capacitor in combination with electrolytic capacitor to reject high frequency noise. The electrolytic capacitor can be low ESR aluminum electrolytic capacitor or polymer aluminum electrolytic capacitor. 9) Inductor selection L1: Caution is required due to the heat generation from choke coil caused by overload and load short. The inductance value is determined by output ripple voltage (Vrip) and the impedance of output capacitor for switching frequency. The minimum inductance is obtained by the equation (19). L min = VOUT × RC VIN - VOUT × Vrip fOSC × VIN [µH] (19) In the above equation, ESR is used in place of the impedance of output capacitor. The reason is, the impedance of output capacitor for switching frequency is close to RC in many cases. However with ceramic capacitor, real impedance is used instead of RC. Ex)VIN(max)=24V, VOUT=12V, Vrip=100mV, RC=9mΩ, fOSC=100kHz L min = 24V - 12V 12V × 9m × 20mV 100k × 24V (20) ≈ 27 [µH] In the actual part selection, ripple voltage is defined first, then capacitor and inductor are selected. Take the maximum value and minimum value of input voltage, output voltage and load variation into consideration. Also, the ripple current of inductor is used as basis for output inductor selection in many cases. Ripple current is obtained by the equation (21). Irip = VIN - VOUT × D [A] fOSC × L (21) D represents duty cycle defined by VOUT/VIN. The important term is the ripple current represented as Irip/IOUT. As long as the ripple element is less than 50%, it should not be a problem. If the ripple element is higher, inductor loss becomes significant. Ex)VIN=24V, VOUT=12V, fOSC=100kHz, L=45μH Irip = 24V - 12V × 0.5 100k × 45µ (22) = 1.3 [A] 10) Power consumption of high side MOSFET The power consumption in the external high side MOSFET is represented by conduction loss and switching loss. The conduction loss of MOSFET is obtained by the following equation (23). Psat = IO2 × RDS(ON) × D [W] (23) Since RDS(ON) is affected by temperature, it is advisable to confirm the actual FET temperature and data sheet. The switching loss of high side MOSFET is obtained by the following equation (24). Psw = VIN × IO × tSW × fSW [W] IO: DC output current tSW: Rise time of switching waveform fSW: Switching frequency (24) PS No.A1988-12/15 LV5768M The junction temperature of high side MOSFET is obtained by the following equation (25). Tj = Ta + (Psat + Psw) × θja [W] θja: Package heat resistor Tj should not exceed the Tjmax as stated in the data sheet. 11) Power consumption of low side MOSFET The power consumption in low side MOSFET consists of conduction loss from RDS (ON) as well as from body diode and reverse recovery loss. The conduction loss due to RDS (ON) is obtainable by the equation (23) which is represented in the equation (26). Psat = IO2 × RDS(ON) × (1-D) [W] (25) (26) The conduction loss from body diode occurs when the body diode is conducted forwardly between high side off and low side off zone, which is represented in the equation (27). Pdf = 2 × IO × Vf × tdelay × fSW [W] Vf: Forward voltage of body diode tdelay: Delay time immediately before surge of SW node The total power consumption of low side MOSFET is obtained by the equation (28). Pls = Psat + Pdf [W] (28) (27) 12) Power consumption of LV5768M The total power consumption of LV5768M is represented in the equation (29) given that the same MOSFET is selected for high side and low side. Pd_ic = (2 × Qg × fSW + ICCA) × VIN [W] ICCA: IC consumption current when switching is stopped. (29) PS No.A1988-13/15 LV5768M • Caution for pattern layout C1: input capacitor When the IC performs switching, ripple current flows into the input capacitor of DC-DC converter. The capacitor of input should be connected adjacent to the power IC and minimize the inductance from pattern layout. C1 should be connected adjacently to VIN pin of the IC and Q1 (high side FET- drain). If implementation to IC side is not feasible, insert adjacently to Q1. C7 (bypass capacitor connected to VIN pin of the IC) should be connected adjacently to VIN pin and GND pin. In rare cases, intensive ringing may occur in the VIN pin by connecting bypass capacitor. The recommendation value is 1000pF. Q1, Q2 (D1): external FET Both high and low sides are driven by Nch-MOSFET. In Q1, a transition of SW node takes place between VIN and GND by turn on and off, where high frequency noise occurs. The noise affects the surrounding pattern layouts and parts. The high/ low side gate and SW node should be laid out as fat and short as possible without connecting all the way to HDRV, LDRV and SW pins of the IC. HDRV, LDRV and SW pins should be shielded with GND to prevent influence from noise. When high side FET is turned on, current path is as follows: VIN + (C1) --> inductor (L) --> VOUT (load) --> PGND --> GND. When low side FET is turned on, current path is as follows: inductor (L) --> VOUT (load) --> PGND. By minimizing the area of current path and keeping the pattern layout fat and short, noise is eliminated and error operation is prevented. Hence, Q1, Q2, D1, C1 and C9 should be implemented nearby. R5,C6: ILIM (overcurrent limiter set pin) ILIM pin detects overcurrent which is used as set point where current limit comparator in the IC starts operation. The overcurrent limiter is adjustable by the resistor between ILIM pin and VIN pin. When the voltage of SW pin becomes lower than that of ILIM pin, current limit comparator functions and turns off the high side MOSFET. This operation is reset at every PWM pulse. To filter unwanted noise, C6 should be connected in parallel to the set resistor (the recommendation is 1000pF). R5 and C6 should be implemented adjacently to the VIN side of the IC. If they are apart from the VIN side, detection precision for overcurrent point may be deteriorated. Small signal system: part for FB, COMP, EN, CBOOT, VDD and SS pins. The parts should be implemented adjacently to the IC and be connected as short as possible. Also the GND of the parts should have common GND pattern as the IC. FB pattern layout should not be under nor nearby the inductor or SW node. This must be complied to avoid error operation. PS No.A1988-14/15 LV5768M SANYO Semiconductor Co.,Ltd. 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 SANYO Semiconductor Co.,Ltd. products described or contained herein. SANYO Semiconductor Co.,Ltd. strives to supply high-quality high-reliability products, however, any and all semiconductor products fail or malfunction with some probability. It is possible that these probabilistic failures or malfunction could give rise to accidents or events that could endanger human lives, trouble that could give rise to smoke or fire, or accidents that could cause damage to other property. When designing equipment, adopt safety measures so that these kinds of accidents or events cannot occur. Such measures include but are not limited to protective circuits and error prevention circuits for safe design, redundant design, and structural design. In the event that any or all SANYO Semiconductor Co.,Ltd. products described or contained herein are controlled under any of applicable local export control laws and regulations, such products may require the export license from the authorities concerned in accordance with the above law. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying and recording, or any information storage or retrieval system, or otherwise, without the prior written consent of SANYO Semiconductor Co.,Ltd. Any and all information described or contained herein are subject to change without notice due to product/technology improvement, etc. When designing equipment, refer to the "Delivery Specification" for the SANYO Semiconductor Co.,Ltd. product that you intend to use. Upon using the technical information or products described herein, neither warranty nor license shall be granted with regard to intellectual property rights or any other rights of SANYO Semiconductor Co.,Ltd. or any third party. SANYO Semiconductor Co.,Ltd. shall not be liable for any claim or suits with regard to a third party's intellctual property rights which has resulted from the use of the technical information and products mentioned above. This catalog provides information as of December, 2011. Specifications and information herein are subject to change without notice. PS No.A1988-15/15