LT1506 Monolithic 4A Switcher 5V to 15V Input 3.3V Output DESCRIPTIO U

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1 EMO MNUL /8 LT10 Monolithic 4 Switcher V to 1V Input.V Output ESRIPTIO U emonstration circuits /8 are complete / step-down regulators using the LT 10, constant frequency, high efficiency converter in -pin (8) and SO-8 () packages. These circuits are primarily used in personal computers, disk drives, portable handheld devices and, in larger systems, as local onboard regulators. High frequency switching allows the use of small inductors, making this all surface mount solution ideal for space conscious systems., LT and LT are registered trademarks of Linear Technology orporation. PERFORmNE SU U W WW RY T =, V IN = 1V, I LO =, V OUT =.V, SHN and SYN pins open, unless otherwise specified. PRMETER ONITIONS MIN TYP MX UNITS Output Voltage (Note 1)...4 V Maximum I LO (Note ) 4 Input Voltage Range 4. 1 V Switching Frequency khz Output Ripple Voltage 0 mv P-P Line Regulation V to 1V mv Load Regulation I LO = 10m to 4 14 mv SHN Lockout Threshold..8.4 V SHN Shutdown Threshold V Synchronization Range Only khz Supply urrent SHN = 0V 0 µ Note 1: Output voltage variations include ±1% tolerance of feedback divider network. For tighter voltage range, use lower tolerance resistors or fixed.v output device, LT10-.. Note : For, additional thermal restrictions apply. OR PHOTOS omponent Side 8 omponent Side 1

2 EMO MNUL /8 TYPIL PERFOR E HRTERISTIS EFFIIENY (%) UW.V Output Efficiency Temperature Rise vs Load urrent 1V IN V IN IE TEMPERTURE RISE ( ) V IN = V V OUT =.V LO URRENT () LO URRENT () /8T01 /8T0 PKGE SHE TI IGR SM W U * MM914LT1 W E1 V IN V TO 1V E SHN E + 10µF V * *MOVE TO POSITION FOR OUTPUT URRENTS > 4 4 1µF 1 OOST V IN U1 SW 8 LT10S8 SHN SYN F V R1 L1.8µH 1 MR8L E SYN 1 100pF 0V + 100µF + R 1.8k 1% R 4.99k 1% SHEM + 0.4µF E V OUT.V/4 E4 V IN 1 OOST F OR SENSE 4 TOP VIEW 8 S8 PKGE 8-LE PLSTI SO LT10S8 V SW SYN SHN V * MM914LT1 8 E1 V IN V TO 1V E SHN E + 10µF V * *MOVE TO POSITION FOR OUTPUT URRENTS > 4 1µF OOST V IN SW U1 LT10R SHN F V 4 1 R1 L1.8µH 1 MR8L 1 100pF 0V + 100µF + R 1.8k 1% R 4.99k 1% 8 SHEM + 0.4µF E V OUT.V/4 E4 T IS FRONT VIEW 4 1 R PKGE -LE PLSTI PK LT10R F OR SENSE OOST V IN V SW SYN OR SHN V

3 PRTS LISTS EMO MNUL /8 REFERENE ESIGNTOR QUNTITY PRT NUMER ESRIPTION VENOR TELEPHONE MTS 100pF 0V XR hip apacitor VX (84) Optional apacitor 1 GRMYV10Z 10µF V YV hip apacitor Murata (814) Z10MTS 1µF XR hip apacitor VX (84) TPS10M010R µF TPS Tantalum apacitor VX (0) ZG44MTS 0.4µF YV hip apacitor VX (84) Optional apacitor 1 1 MR8L SMT iode Motorola (800) MM914LT1 1N914 iode Motorola (800) Optional iode E1 to E 01- Pad Turret Mill-Max (1) R1 0 Optional Resistor R 1 R10-181F-T 1.8k 1/8W 1% hip Resistor Tad (14) -91 R 1 R F-T 4.99k 1/8W 1% hip Resistor Tad (800) L1 1 O1P-8.8µH 0% Inductor oilcraft (84) U1 1 LT10S8 SO-8 Linear I LT (408) P 1 Stencil Stencil 8 REFERENE ESIGNTOR QUNTITY PRT NUMER ESRIPTION VENOR TELEPHONE MTS 100pF 0V XR hip apacitor VX (84) Optional apacitor 1 GRMYV10Z 10µF V YV hip apacitor Murata (814) Z10MTS 1µF XR hip apacitor VX (84) TPS10M010R µF TPS Tantalum apacitor VX (0) ZG44MTS 0.4µF YV hip apacitor VX (84) Optional apacitor 1 1 MR8L SMT iode Motorola (800) MM914LT1 1N914 iode Motorola (800) Optional iode E1 to E 01- Pad Turret Mill-Max (1) R1 0 Optional Resistor R 1 R10-181F-T 1.8k 1/8W 1% hip Resistor Tad (14) -91 R 1 R F-T 4.99k 1/8W 1% hip Resistor Tad (800) L1 1 O1P-8.8µH 0% Inductor oilcraft (84) U1 1 LT10R -Pin Pak Linear I LT (408) P 1 8 Stencil Stencil

4 OPERTIO U EMO MNUL /8 vs 8 (Temperature vs Package Size) The and 8 demonstration boards are intended for evaluation of the LT10 switching regulator in the SO-8 and -pin packages respectively. The -pin package used in 8 has no SYN pin, but a version (LT10R-SYN) replaces the SHN function at Pin with the SYN function. The primary reason for choosing the SO-8 over the package is board space. The 8 ( package) occupies an active board area of approximately 0. square inches. Optimizing the board, using a Sumida coil and removing the layout options, a total active area of 0.4 square inches is possible. The package is more suitable for higher power or higher ambient temperature applications. lthough both boards will supply 4 of output current, must be thermally derated to continuous at ambient to prevent excessive die temperatures. 8 can run at 0 ambient at 4 output current. However, the SO-8 package can be used for dynamic loads up to the full rated switch current. LT10 Operation The LT10 data sheet gives a complete description of the part, operation and applications information. The data sheet should be read in conjunction with this demo manual. Hook-Up Solid turret terminals are provided for easy connection to supplies and test equipment. onnect a 0V to 1V, 4. power supply across the V IN and terminals and the load across the V OUT and terminals. When measuring load/line regulation, remember to Kelvin connect to the turrets. lso, when measuring output ripple voltage with an oscilloscope probe, the wire from the probe to the ground clip will act as an antenna, picking up excessive noise. For improved results, the test hook should be removed from the tip of the probe. The tip should be touched against the output turret, with the bare ground shield pressed against the ground turret. This reduces the noise seen on the waveform. Shutdown For normal operation, the SHN pin can be left floating. SHN has two output-disable modes: lockout and 4 shutdown. When the pin is taken below the lockout threshold, switching is disabled. This is typically used for input undervoltage lockout. Grounding the SHN pin places the LT10 in shutdown mode. This reduces total board supply current to 0µ. Synchronization Synchronization is vailable on Only (SYN is an Optional Replacement for SHN on the Package).For normal demo board operation, the SYN pin can be left floating. If unused in the application, it is advisable to tie this pin to ground. To synchronize switching to an external clock, apply a logic-level signal to the SYN pin. The amplitude must be from a logical low to greater than.v, with a duty cycle from 10% to 90%. The synchronization frequency must be greater than the freerunning oscillator frequency and less than 1MHz. dditional circuitry may be required to prevent subharmonic oscillation. Refer to the LT10 data sheet for more details. OMPONENTS Inductor L1 The inductor is a oilcraft O1P-8, a.8µh unshielded ferrite unit. It was selected for its low cost, small size and 4. I ST rating. The equivalent oiltronics UP-R8 unit can be substituted. If board space is at a premium and higher ripple current is acceptable, solder pads are available for the Sumida 4-1R8 inductor. This 1.8µH unit has a.9 I ST rating. Ripple at V IN is ±1.1. This gives a maximum output current of (4. 1.1) =.4. Input/Output apacitors,, and The input capacitor is a Tokin ceramic capacitor. It was selected for its small size, high voltage rating and low ESR (effective series resistance). The input ripple current for a buck converter is high, typically I OUT /. Tantalum capacitors become resistive at higher frequencies, requiring careful ripple-rating selection to prevent excessive heating. eramic capacitors ESL (effective series inductance) tends to dominate their ESR, making them less susceptible to ripple-induced heating.

5 EMO MNUL /8 OPERTIO U The output capacitor is an VX tantalum capacitor. ceramic is not recommended as the main output capacitor since loop stability relies on a resistive characteristic at higher frequencies to form a zero. The VX TPS series was specifically designed for switch-mode power supplies to have very low ESR. t switching frequencies, ripple voltage is more a function of ESR than of absolute capacitance value. If lower output ripple voltage is required, use the optional capacitor to reduce ESR rather than increasing the capacitance of. For very low ripple, an additional L filter in the output may be a less expensive solution. The output contains very narrow voltage spikes because of the parasitic inductance of. small ceramic capacitor,, removes these spikes on the demo board. In application, trace inductance and local bypass capacitors will perform this function, negating the need for. atch iode 1 Use diodes designed for switching applications, with adequate current rating and fast turn-on times, such as Schottky or ultrafast diodes. In selecting a diode, the basic parameters of interest are forward voltage, maximum reverse voltage, average operating current and peak current. Lower forward voltage yields higher circuit efficiency and lowers power dissipation in the diode. The MR8L has a maximum forward drop of 0.4V at. The reverse voltage rating must be greater than the input voltage. verage diode current is always less than output current, but under a shorted output condition, diode current can equal switch current limit. If the application must withstand this condition, the diode must be rated for maximum switch current. ompensation: 1, and R1 detailed discussion of frequency compensation can be found in the LT10 data sheet. 1, a 100pF capacitor from V to ground, gives a stable loop response over a wide range of input and output conditions. Options R1 and are included for optimization of the dynamic response to a specific application. oost Voltage:, and 4 boost voltage of at least.8v is required throughout the on-time of the switch to guarantee that it remains saturated. t output currents greater than and higher ambient temperatures, diode must be moved to position to prevent boost from falling below this minimum. For output voltages above.v, diode provides sufficient boost voltage to 4. P LYOUT In many cases, the layout of the demonstration board may be dropped directly into the application with minimal changes. If not, there are several precautions that must be taken when laying out high frequency converter circuits. The high frequency switching path runs from ground, through, to the V IN pin of the LT10, out of the SW pin, through 1 and back to ground. This loop acts as an antenna and will radiate noise if not kept as short as possible. lso, at higher switching currents, the associated trace inductance can cause excessive voltage spikes across the switch. The use of a ground plane will reduce many noise problems. The ground pin of the LT10 contains some high frequency signal currents, but more importantly, it is the 0V reference for the output voltage. onnect the ground pin directly to the ground plane. The F and V components should be kept away from the power components as much as possible. The ground for these components should be separated from power grounds. Run a Kelvin sense to V OUT as required but keep the divider network close to the LT10 to prevent noise pickup on the F node. Noise pickup on the V pin appears as various problems, including poor load regulation, subharmonic oscillation and instability. Thermal management must also be considered. The SO-8 package has a fused ground pin. Soldering this pin to a large copper area will significantly reduce its thermal resistance. Solder-filled feedthroughs close to the ground pin provide a good thermal path to the ground plane. For the package, the grounded tab should be treated in the same manner. For more information or advice, contact the LT pplications department.

6 EMO MNUL /8 U W P LYOUT FIL () omponent Side Silkscreen omponent Side omponent Side Solder Mask omponent Side Paste Mask Solder Side Solder Side Solder Mask

7 EMO MNUL /8 U W P LYOUT FIL (8) omponent Side Silkscreen omponent Side omponent Side Solder Mask omponent Side Paste Mask Solder Side Solder Side Solder Mask Information furnished by Linear Technology orporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology orporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.

8 EMO MNUL /8 P F RWI GS U.000".000" NOTES: UNLESS OTHERWISE SPEIFIE 1. MTERIL: FR4 OR EQUIVLENT EPOXY, OZ OPPER L, THIKNESS 0.0 ±0.00 TOTL OF LYERS. FINISH: LL PLTE HOLES MIN/0.001 MX OPPER PLTE, ELETROEPOSITE TIN-LE OMPOSITION EFORE REFLOW, SOLER MSK OVER RE OPPER (SMO). SOLER MSK: OTH SIES USING SR100 OR EQUIVLENT 4. SILKSREEN: USING WHITE NONONUTIVE EPOXY INK. LL IMENSIONS IN INHES. SORING 0.01 SYMOL IMETER TOTL HOLES NUMER OF HOLES 8 F 8.000".000" NOTES: UNLESS OTHERWISE SPEIFIE 1. MTERIL: FR4 OR EQUIVLENT EPOXY, OZ OPPER L, THIKNESS 0.0 ±0.00 TOTL OF LYERS. FINISH: LL PLTE HOLES MIN/0.001 MX OPPER PLTE, ELETROEPOSITE TIN-LE OMPOSITION EFORE REFLOW, SOLER MSK OVER RE OPPER (SMO). SOLER MSK: OTH SIES USING GREEN SR100 OR EQUIVLENT 4. SILKSREEN: USING WHITE NONONUTIVE EPOXY INK. LL IMENSIONS IN INHES. SORING 0.01 SYMOL IMETER TOTL HOLES NUMER OF HOLES 0 8 F 8 Linear Technology orporation 10 Mcarthy lvd., Milpitas, (408) FX: (408) dc8f LT/TP PRINTE IN US LINER TEHNOLOGY ORPORTION 1999