ADT7310 General Description The ADT7310 is system specific power supply IC that is suitable for color CCD camera. ADT7310 Other features include over-current protection, YYWW thermal shutdown. It reduces design complexity and external component count. Package outline of the ADT7310 Features Applications • Input voltage range : 4.75V to 18V • Color CCD camera • Multiple output voltage channel available • CCTV camera - 2 channel 3.3V outputs , 200mA / 60mA max. • distributed power system - 1.8V output , 40mA max. (3.3V / 1.8V / 5V / 15V / -7V) - 5V boost converter output , 100mA max. - 15V output , 10mA max. - Externally adjustable negative voltage output (-7V typical) • Power-on-reset output & power sequence • Protection : thermal shutdown , over-current protection • Small size(5x5 mm2 body) and thermally enhanced 28 Pin MLF Package Typical Application Circuit U1 CL1 CF1 L2 D2 VIN QN1 5V 1.8V C2 CL7 C20 Rs2 C100 U2 CF2 C200 CL2 Rs1 QP1 CF3 U0 (ADT7310) C10 Rn2 L1 D1 VIN2 U3 -7V Rn1 CL3 15V C1 CL6 C30 Ct CL4 CL5 RBO 3.3VD C40 3.3VA * This specifications are subject to be changed without notice Oct. 17. 2008 / Rev. 0.0 1/15 http://www.ad-tech.co.kr ADT7310 Part List Component Type Value ( Model ) Manufacturer U0 IC ADT7310 ADTech U1, 2, 3 IC BAT54SWT1 ON Semiconductor QP1 Chip transistor 2SB1424 ROHM QN1 Chip transistor MMBT4401LT1 ON Semiconductor Chip SBD RSX101M-30 ROHM L1 Chip inductor 47uH / 590mA (SLF6028T-470MR59) TDK L2 Chip inductor 47uH / 590mA (SLF6028T-470MR59) TDK C1 , 2 MLCC 10uF / 10V / X5R Murata C100 Tantalum capacitor 10uF / 25V (T91C106K025AT) KEMET C200 MLCC 0.1uF / 25V - CF1 , 2 , 3 MLCC 1uF / 25V / X5R Murata CL1 , 2 , 3 MLCC 2.2uF / 25V / X5R Murata C10 MLCC 1nF - C20 MLCC 22nF - C30 MLCC 22nF - Ct MLCC 18pF - CL4, 5, 7 MLCC 2.2uF / 25V / X5R Murata CL6 MLCC 4.7uF / 25V / X5R Murata C40 MLCC 10nF - Rs1 , 2 Chip resistor 0.1Ω / 1% - Rn1 Chip resistor 45.3㏀ / 1% - Rn2 Chip resistor 12.1㏀ / 1% - D1, D2 ※ SBD (Schottky Barrier Diode) * This specifications are subject to be changed without notice Oct. 17. 2008 / Rev. 0.0 2/15 http://www.ad-tech.co.kr ADT7310 Pin Configuration 28 27 26 25 24 23 22 1 21 2 20 3 19 ADT7310 4 5 17 6 16 7 15 8 Pin Description 18 9 10 11 12 13 14 I : Input , O : Output , IO : Input/Output , P : Power , G : Ground , A : Analog , D : Digital Pin No. Name I/O Type Description 1 RS2 I A Current sensing and voltage feed-forward for boost converter 2 VIN1 - P Main power input 3 RS1 I A Current sensing and voltage feed-forward for buck converter 4 PWM O D PWM output for buck converter 5 CC1 O A Capacitor terminal for phase compensation of buck converter 6 GND2 - G Ground 7 VIN2 - P Second power input 8 VO1 O A 3.3V output for digital part 9 GND3 - G Ground 10 DLY O A Delay time control for RBO signal 11 RBO O D Power on reset output 12 CT O A Capacitor terminal for tuning oscillation frequency 13 VO2 O A 3.3V output for analog part 14 GND4 - G Ground 15 VHO O A 15V output for CCD positive voltage 16 VREG O A Internal reference voltage output 17 VNO1 I A Feedback voltage input for VNO (-7V typical) 18 DRV3 O D Driving signal output of charge pump inverter 19 GND5 - G Ground 20 VIN5 - P Power input for 15V output 21 DRV2 O D Driving signal output of charge pump doubler 22 VIN4 - P Power input for charge pump block 23 GND6 - G Ground 24 VLO O A 1.8V output 25 VIN3 - P Feedback voltage input for boost converter 26 DRV1 O D PWM output for boost converter 27 CC2 O A Capacitor terminal for phase compensation of boost converter 28 GND1 - G Ground * This specifications are subject to be changed without notice Oct. 17. 2008 / Rev. 0.0 3/15 http://www.ad-tech.co.kr ADT7310 Functional Block Diagram RS2 CC2 DRV1 VIN1 5V 1.8V PWM controller Internal Reg BIAS LDO VIN4 OSC C/P doubler DRV2 VIN5 Thermal Shutdown RS1 PWM PWM controller Power Sequencer C/P inverter DRV3 feedback VNO1 CC1 VIN2 LDO POR LDO 3.3VD RBO 3.3VA LDO 15V * This specifications are subject to be changed without notice Oct. 17. 2008 / Rev. 0.0 4/15 http://www.ad-tech.co.kr ADT7310 Absolute Maximum Ratings Parameter Symbol Min. Typ. Max. Unit VIN - - 20 V Power dissipation (Ta=70℃) *1 PDmax - - 2.2 W Storage temperature TSTG -65 - +150 ℃ Junction temperature TJmax - - +150 ℃ Thermal resistance ΘJA - 35 - ℃/W Power supply voltage *1 derate 35℃/W above +70℃. Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Operating Ratings Parameter Symbol Min. Typ. Max. Unit Power supply voltage VIN 4.75 12 18 V Operating temperature TOPR -20 - +85 ℃ Junction temperature TJ - - +125 ℃ Max. power dissipation (Ta=70℃)*1 PD - - 1.5 W *1 This spec. indicates that junction temperature of the device is under 125℃. In specific applications, this is recommended under this power dissipation specification. Electrical Characteristics (Ta = 25℃ , VIN = 12V , unless otherwise noted.) Parameter Condition Min Typ Max Unit - 4.75 12 18 V VIN=12V, w/o loading 5.0 8.0 11.0 ㎃ VIN=12V , C30 =22㎋ - 8.5 - ㎳ 3.0 3.3 3.6 V Note Basic Function Operating supply voltage ICC with no load Tdelay Power on reset VOH Over-temperature protection - On Junction temperature at OT enable - 140 - ℃ Off Junction temperature at OT release - 110 - ℃ VIN=12V , max. load current - 58 - ％ Continuous mode , Ct=13㎊ 400 500 600 ㎑ Note1 Continuous mode , Ct=18㎊ 300 400 500 ㎑ Note2 VIN=12V 3.5 3.7 3.9 V Efficiency Switching frequency Buck Converter (+3.7V output) Output voltage (VIN2) * This specifications are subject to be changed without notice Oct. 17. 2008 / Rev. 0.0 5/15 http://www.ad-tech.co.kr ADT7310 Electrical Characteristics (continued) Parameter Condition Min. Typ. Max. Unit 3.0 3.3 3.6 V Note +3.3VD output VIN=12V , IO=180㎃ Output voltage Output drive current VIN=12V - 180 200 ㎃ Current limit VIN=12V - 480 - ㎃ Load regulation IO=0 to 200㎃ - 90 200 ㎷ Ripple rejection IO=200㎃ , freq=10㎑ - 40 - ㏈ 3.0 3.3 3.6 V +3.3VA output Output voltage VIN=12V , IO=50㎃ Output drive current VIN=12V - 50 60 ㎃ Current limit VIN=12V - 180 - ㎃ Load regulation IO=0 to 60㎃ - 60 100 ㎷ Ripple rejection IO=60㎃ , freq=10㎑ - 40 - ㏈ VIN=12V , IO=25㎃ 1.7 1.8 1.9 V +1.8V output Output voltage Output drive current VIN=12V - 25 40 ㎃ Current limit VIN=12V - 200 - ㎃ Load regulation IO=0 to 40㎃ - 20 40 ㎷ Ripple rejection IO=40㎃ , freq=10㎑ - 40 - ㏈ 14.55 15.00 15.45 V +15V output VIN=12V , IO=5㎃ Output voltage Output drive current VIN=12V - 5 10 ㎃ Current limit VIN=12V - 20 - ㎃ IO=0 to 10㎃ - 30 50 ㎷ -7.5 -7.0 -6.5 V Inflow current - 2 5 ㎃ Io=0 to -5㎃ - 30 100 ㎷ 4.75 5.00 5.25 V - 50 100 ㎃ Load regulation -7V output (Rn1=45.3㏀ , Rn2=12.1㏀ , unless otherwise noted.) Output voltage VIN=12V , Io=-2㎃ Output drive current Load regulation Boost Converter (+5V output) Output voltage (VIN3) Maximum output current VIN=12V , IO=80㎃ VIN=12V Note 1. This switching frequency is suitable to 5V VIN operating condition. Note 2. This switching frequency is suitable to 12V VIN operating condition. * This specifications are subject to be changed without notice Oct. 17. 2008 / Rev. 0.0 6/15 http://www.ad-tech.co.kr ADT7310 Typical Performance Characteristics 3.3VA Change vs Temperature 3.0 2.0 2.0 3.3VA Change (%) 3.3VD Change (%) 3.3VD Change vs. Temperature 3.0 1.0 0.0 -1.0 1.0 0.0 -1.0 -2.0 -2.0 -3.0 -3.0 -20 0 20 40 60 80 Temperature (℃) 100 120 -20 0 3.0 2.0 2.0 1.0 0.0 -1.0 -2.0 120 1.0 0.0 -1.0 -2.0 -3.0 -3.0 -20 0 20 40 60 80 Temperature (℃) 100 120 -20 0 15V Change vs Temperature 3.0 2.0 2.0 1.0 0.0 -1.0 -1.0 -3.0 -3.0 20 40 60 80 Temperature (℃) 100 120 0.0 -2.0 0 100 1.0 -2.0 -20 20 40 60 80 Temperature (℃) -7V Change vs Temperature 3.0 -7V Change (%) 15V Change (%) 100 1.8V Change vs Temperature 3.0 1.8V Change (%) 5V Change (%) 5V Change vs Temperature 20 40 60 80 Temperature (℃) 120 -20 0 20 40 60 80 Temperature (℃) 100 120 * This specifications are subject to be changed without notice Oct. 17. 2008 / Rev. 0.0 7/15 http://www.ad-tech.co.kr ADT7310 Typical Performance Characteristics Switching Frequency vs Temperature Efficiency vs Load Current (Buck) 100 500 VIN=5V 450 80 Efficiency (%) Frequency (kHz) 475 425 400 375 350 VIN=12V VIN=18V 60 40 325 300 20 -20 0 20 40 60 80 Temperature (℃) 100 120 0 200 400 600 Load Current (mA) 800 1000 * This specifications are subject to be changed without notice Oct. 17. 2008 / Rev. 0.0 8/15 http://www.ad-tech.co.kr ADT7310 Operation Description DEVICE INFORMATION Note that external resistors for tuning negative voltage output The ADT7310 includes one step down DC-DC switching buck required as accurate as possible. It is recommended 1% accur- converter, one step up DC-DC switching boost converter, cha- acy. Because -7V output is generated by two cascaded charge rge pump boost converter, charge pump inverting converter, pump converter, this channel has operating voltage limitation. and several LDOs. With the operation above -7.5V, it is saturated and its regulati- Especially produced for powering CCD camera applications, on performance degraded. this device provides various power channels for composing the +15V channel is generated with two cascaded charge pump co- CCD applied camera system. These channel are 3.3V, 5V, 15V nverters and one LDO. This channel output supplied current to , -7V and 1.8V. From these channel, it is possible to supply CCD device. So, its channel output noise affects image to noi- all the powers required for the application in one power supply se directly. This is why one LDO is added and therefore the device, ADT7310. ADT7310 provides clear +15V output to the system. The ADT7310 is assembled with small size and thermally enhanced MLF (Micro Lead Frame) package. LDO With wide input operating voltage range and one stop power This device has four LDOs integrated (+3.3V 2 channel, +15V supply configuration, it is very easy to design new specific set. and +1.8V channel). Because the ADT7310 provided for using CCD camera application, the noise of each channel output mu- BUCK CONVERTER st be minimized. Integration of LDOs trade off noiseless output Buck converter generates internal supply voltage (approxima- and heat dissipation performance of the device. From these tely 3.7V). As required wide input supply range from 4.75V to aspect, each channel load capability and input-output dropout 18V, intermediate power is needed. From this intermediate conditions are designed. By these considerations this device power all the channel outputs re-generated. Using a current provides optimum application function. Note that the heavy mode architecture with asynchronous rectification, the buck load current and high line voltage application will produce the- converter have the ability to deliver sufficient current to the mal constraint. following power supply channels. POWER ON SEQUENCE BOOST CONVERTER CCD camera application made by various devices requires ma- 5V output channel is generated by the boost converter. Operat- ny different supply voltages. Also with different operating rati- ing with current mode step-up DC-DC converter, its input volt- ng between devices, it is seriously considered to power up se- age is buck converter output voltage (3.7V typical). With this quence. Fortunately CCD camera application has only two cri- boost converter output, supplied the power at the following tical power supplies, +15V and -7V for powering the CCD. charge pump converters for generating +15V and -7V output. Power on sequence that the system needs is as follows : Also it is provided +5V output with 100mA load current inde- i) the -7V must be supplied lastly. pendently. In case of upper 100mA load, must be considered ii) the +15V must be supplied before the -7V. the device’s heat dissipation constraint. iii) other power supplies have no order. Followed by the upper sequence, the ADT7310 operate succe- CHARGE PUMP CONVERTER ssfully when it is powered up. Further the ADT7310 will mon- By these converters the ADT7310 provides +15V and -7V cha- itor +3.3V channel voltage and generate RBO signal to reset nnel outputs. For these two channel generation, it is used three the DSP device. This RBO signal also follows after the -7V charge pump converters, one with externally composed and channel settling. others with integrated. In case of generating charge pump inve- VIN rter the part of the inverter are placed at the outside of the devi-7V ce for its inherent limitation of negative voltage operation. -7V +15V inverter is possible to change its output voltage by tuning the RBO external resistors. * This specifications are subject to be changed without notice Oct. 17. 2008 / Rev. 0.0 9/15 http://www.ad-tech.co.kr ADT7310 Application Hints LDO CONSIDERATIONS re range of -55℃ to +125℃, will only vary the capacitance to EXTERNAL CAPACITORS The ADT7310’s regulators requires external capacitors for within ±15%. The capacitor type X5R has a similar tolerance regulator stability. These are specifically designed for CCTV over a reduced temperature range of -55℃ to +85℃. Many camera applications requiring minimum board space and large value ceramic capacitors, larger than 1uF are manufactu- smallest components. These capacitors must be correctly sel- red with Z5U or Y5V temperature characteristics. Their capa- ected for good performance. citance can drop by more than 50% as the temperature varies from 25℃ to +85℃. Therefore X7R is recommended over OUTPUT CAPACITOR Z5U and Y5V in applications where the ambient temperature The LDO’s are designed specifically to work with small cera- will change significantly above or below 25℃. mic output capacitors. And each LDO’s has its own output capacitor ranges. Be sure to be connected proper output capa- Tantalum capacitors are less desirable than ceramic for use as citor between the output pin and ground. output capacitors because they are more expensive when com- For using MLCC, output capacitor value is good to use more paring equivalent capacitance and voltage ratings in the 0.47uF than that of the specified to ‘Typical Application Circuit’. to 4.7uF range. And its required ESR range are between 10mΩ to 1Ω. Another important consideration is that tantalum capacitors have higher ESR values than equivalent size ceramics. This mea- The output capacitor must meet the requirement for the min- ns that while it may be possible to find a tantalum capacitor imum value of capacitance and also have an ESR value that with an ESR value within the stable range, it would have to be is within the optimum range for stability. larger in capacitance than a ceramic capacitor with the same ESR value. It should also be noted that the ESR of a typical The LDO’s will remain stable and in regulation with no ext- tantalum will increase about 2:1 as the temperature goes from ernal load. 25℃ down to -40℃, so some guard band must be allowed. CAPACITOR CHARACTERISTICS BUCK CONSIDERATIONS The LDO’s are designed to work with ceramic capacitors on the output to take advantage of the benefits they offer. For INDUCTOR SELECTION capacitance values in the range of 0.47uF to 4.7uF, ceramic There are two main considerations when choosing an inductor; capacitors are the smallest, least expensive and have the low- the inductor should not saturate, and the inductor current ripple est ESR values, thus making them best for eliminating high is small enough to achieve the desired output voltage ripple. frequency noise. The ESR of a typical 1.0uF ceramic capacitor Different saturation current rating specs are followed by differ- is in the range of 20mΩ to 40mΩ. ent manufacturers so attention must be given to details. Satura- The capacitor value can change greatly, depending on the oper- tion current ratings are typically specified at 25℃ so rating at ation conditions and capacitor type. So, the output capacitor max ambient temperature of application should be requested selection should take account of all the capacitor parameters, from manufacturer. to ensure that the specification is met within the application. The capacitance can vary with DC bias conditions as well as The saturation current is greater than the sum of the maximum temperature and frequency of operation. Normally increasing load current and the worst case average to peak inductor curr- the DC bias condition can result in the capacitance value fall- ent. A 47uH inductor with a saturation current rating of at least ing below the minimum specified limit. It is therefore recom- 590mA is recommended in this application. The inductor’s res- mended that the capacitor manufacturer’s specifications for istance should be as low as possible for better efficiency. For the nominal value capacitor are consulted for all conditions. CCTV camera application, radiated RF noise from inductor is critical for high definitive video image. In this application, The ceramic capacitor’s capacitance can vary with temperatu- a toroidal or shielded bobbin inductor should be used. re. The capacitor type X7R, which operates over a temperatu- * This specifications are subject to be changed without notice Oct. 17. 2008 / Rev. 0.0 10/15 http://www.ad-tech.co.kr ADT7310 Application Hints (continued) where OUTPUT CAPACITOR SELECTION IOUTMAX : maximum load current L : min. inductor value including worst case tolerance Use a 10uF, 10V ceramic capacitor. Use X7R or X5R types, do not use Y5V. The output filter capacitor smoothes out current flow from the CHARGE PUMP CONSIDERATIONS inductor to the load, helps maintain a steady output voltage during transient load changes and reduces output voltage ripple. DOUBLER / INVERTER CAPACITOR SELECTION These capacitors must be selected with sufficient capacitance The flying capacitor (CF*) transfers charge from the its input and sufficiently low ESR to perform these functions. power supply to the output. A polarized capacitor (tantalum, The output voltage ripple is caused by the charging and disch- aluminum electrolytic, etc.) must not be used here, as the arging of the output capacitor and also due to its ESR and can capacitor will be reverse biased upon start-up of the ADT7310. be calculated as : The size of the flying capacitor and its ESR affect output cur- Voltage peak-to-peak ripple due to capacitance can be express- rent capability and ripple characteristic. In this applications, ed as follows a 1uF, X7R or X5R type ceramic capacitor is recommended VPP-C = IRIPPLE / (4 * f * C) for the flying capacitor. where IRIPPLE : Average to peak inductor current f : Minimum switching frequency The load capacitor (CL1,2,3) of the charge pump plays an imp- Voltage peak-to-peak ripple due to ESR can be expressed as ortant part in determining the characteristics of the doubler follows output. The ESR of the output load capacitor affects charge VPP-ESR = (2 * IRIPPLE) * RESR pump output resistance, which plays a role in determining Because these two components are out of phase the rms value output current capability. Both output capacitance and ESR can be used to get an approximate value of peak-to-peak affect output voltage ripple. For these reasons, a low value ripple. ESR capacitor is recommended. Voltage peak-to-peak ripple, root mean squared can be expressed as follows BOOST CONSIDERATIONS VPP-RMS = √ (VPP-C2 + VPP-ESR2) Note that the output voltage ripple is dependent on the inductor current ripple and the ESR of the output capacitor. The ESR As previously mentioned from the inductor selection at the is frequency dependent (as well as temperature dependent), buck converter, inductor at the boost converter also needs to be make sure the value used for calculations is at the switching considered two factors when choosing an inductor; frequency of the part. the inductor should not saturate, and the inductor current ripple is small enough to achieve the desired output voltage ripple. INPUT CAPACITOR SELECTION By the property of cascading boost converter from buck conv- The ADT7310 uses 10uF, 25V tantalum capacitor for input capacitor. Use a mix of input bypass capacitors to control the voltage overshoot. Use ceramic capacitor for the high frequency decoupling and tantalum capacitor to supply the required rms input current. Place the input capacitor as close as possible to the VIN pin of the device. The input filter capacitor supplies current to the PNP switching transistor of the converter in the first half of each cycle and reduces voltage ripple imposed on the input power source. The input current ripple can be calculated as : I RMS INDUCTOR SELECTION V = I OUTMAX ∗ 1 − OUT VIN ⎛V r2 ⎞ ∗ ⎜⎜ OUT + ⎟⎟ ⎝ VIN 12 ⎠ erter, its inductor saturation current is lower than the that of the buck converter. In this application, the same 47uH adopted and is sufficient. Boost converter drives both its load current and the following charge pump converters for generating +15V and -7V. For proper operation at the power up time this inductor needs more saturation current than its total load current required. OUTPUT CAPACITOR SELECTION Use a 10uF, 10V ceramic capacitor. Use X7R or X5R types, do not use Y5V. (the same component as buck converter) (V − VOUT ) ∗ VOUT r = IN L ∗ f ∗ I OUTMAX ∗ VIN * This specifications are subject to be changed without notice Oct. 17. 2008 / Rev. 0.0 11/15 http://www.ad-tech.co.kr ADT7310 Application Hints (continued) The output filter capacitor smoothes out current flow from the inductor to the load, helps maintain a steady output voltage during transient load changes and reduces output voltage ripple . These capacitors must be selected with sufficient capacitance and sufficiently low ESR to perform these functions. Though the output ripple at the boost converter is not critical at the CCD camera application, care must be needed because its output ripple attacks other power supplies composed in the board to add ripple voltage noise and induce noise at the image. So, if produced output ripple don’t affect to the image than it is recommended to choose one by considering component cost. * This specifications are subject to be changed without notice Oct. 17. 2008 / Rev. 0.0 12/15 http://www.ad-tech.co.kr ADT7310 PCB design for optimized thermal performance 1. Overview Temperature characteristic of the ADT7310 is dependant to power dissipation and heat away of the PCB pattern. Therefore, in design of the PCB pattern, Consideration of the heat away characteristic is important. ADT7310 package is designed to provide enhanced thermal characteristics through the exposed PAD on the bottom surface of the package. Exposed PAD effectively decrease the thermal resistance, which in turn provides excellent heat dissipation from the die. In order to take full advantage of exposed PAD, the PCB must have features to effectively conduct heat away from the package. This can be achieved by incorporating thermal PAD and thermal VIAs. PCB to the bottom layers, thermal VIAs need to be incorporated into the thermal pad design. The number of thermal VIAs improve the package thermal performance. Generally, web-constructed VIA is often used in through-hole applications to facilitate the soldering of a pin to a large plane. It has a large thermal resistance to the surrounding layer. For this reason, do not use web-constructed VIA to the thermal PAD. It is recommended use completely connected VIA to the surrounding layer (Figure 2). If the diameter of the VIAs is too large, solder will be pulled away from the exposed paddle (solder wicking) during the reflow process. This will decrease thermal characteristic of the VIA 2. PCB Layout considerations 2.1 Heat transfer For enhanced thermal performance, the exposed PAD on the package needs to be soldered to thermal PAD on the PCB. Furthermore, for proper heat conduction through the PCB, thermal VIAs need to be incorporated in the PCB in the thermal PAD region. The exposed PAD should be attached to the ground plane for proper thermal and electrical performance. Figure 1 illustrates primary heat away through GND layer of the PCB. The presence of large metal planes in the PCB can heat away 90% of the generated heat in the ADT7310 (Reference 1) <Figure 2. Thermal Landing and Thermal VIA> 3. Recommended PCB patterns Figure 3 and 4 show adoptive PCB pattern of the ADT7310. Top and bottom of the thermal PAD patterns are the same and connected through the thermal VIAs. Also the bottom thermal PAD must be connected to adjacent ground plane. It is recommended that an array of thermal VIAs should be incorporated at 1.0 to 1.2mm pitch with VIA diameter of 0.3 to 0.33mm. <Figure 1. Heat transfer> 2.2 Thermal PAD To maximize thermal performance, the size of the thermal PAD should at least match the exposed PAD size. The size of the thermal PAD on the bottom PCB layer should be at least as large as the thermal PAD on the top PCB layer. It is recommended that the bottom thermal PAD be thermally connected to a GND layer (Reference 2) 2.3 Thermal VIAs In order to effectively transfer heat from the top layer of the <Figure 3. PCB land pattern – Top Layer> * This specifications are subject to be changed without notice Oct. 17. 2008 / Rev. 0.0 13/15 http://www.ad-tech.co.kr ADT7310 PCB design for optimized thermal performance <Figure 4. PCB land pattern – Bottom Layer> 4. Stencil MASK In order to effectively remove the heat from the package and to enhance electrical performance the exposed PAD needs to be soldered to the thermal PAD, preferably with minimum voids. If the solder paste coverage is too big, out gassing occurs during reflow process which may cause defects (splatter, solder balling). Therefore, It is recommended that smaller multiple openings in stencil should be used instead of one big opening for printing solder paste on the thermal PAD region (Figure 5). This will typically result in 50 to 80% solder paste coverage 1.0mm dia. Circles @1.2mm Pitch <Figure 5. Thermal PAD stencil MASK> 5. Reflow condition Reflow profile and peak temperature has a strong influence on void formation. Voids in the thermal PAD region reduce as the peak reflow temperature is 250~270℃. Solder extrusion from the bottom side of the PCB reduces as the reflow temperature is reduced. Reference : 1. B.Guenin, “Packaging: Designing for Thermal Performance.” Electronics Cooling, May1997. 2. Application Note: “Application Notes for Surface Mount Assembly of Amkor’s Micro Lead Frame ( MLF) Packages.” Amkor Technology, March2001 * This specifications are subject to be changed without notice Oct. 17. 2008 / Rev. 0.0 14/15 http://www.ad-tech.co.kr ADT7310 Package ; 28MLF, 5mm x 5mm body (units : mm) TOP VIEW SIDE VIEW BOTTOM VIEW * This specifications are subject to be changed without notice Oct. 17. 2008 / Rev. 0.0 15/15 http://www.ad-tech.co.kr