QUICK START GUIDE FOR DEMONSTRATION CIRCUIT MHZ DUAL STEP-DOWN DC/DC CONVERTER LT1940 DESCRIPTION

Transcription

1 QUIK STRT GUIE FOR EMONSTRTION IRUIT 9.MHZ UL STEP-OWN / ONVERTER LT90 ESRIPTION emonstration circuit 9 is a.mhz dual step-down / switching converter using the LT90. The LT90 features fast switching speed, two.6 internal power switches, and a wide input voltage range, making it a versatile and powerful I that fits easily into space-constrained applications and removes the need for two separate dc/dc converters in dual output step-down applications. The constant.mhz switching frequency allows for the use of tiny, surface mount external components. The current-mode control topology yields fast transient response and good loop stability, requiring a minimum number of external compensation components and allowing the use of ceramic input and output capacitors. The anti-phase switching and single-i solution require the use of only a single input capacitor. The low resistance internal power switches (0.Ω) maintain high efficiencies (as high as 90%) over a wide range of input voltages and loads. Its 0µ shutdown current (activated via the Run/SS pins) extends battery life. The wide V IN range of the LT90 allows step-down configurations with up to V input. The demonstration board has two circuits to demonstrate both the small space that the monolithic dual step-down converter can achieve with high currents and a single I as well as the versatility and maximum power output of the I. The circuit demonstrating smallest size generates.v at up to and.8v at up to output from a.8vv input. The larger, more versatile circuit generates V at up to. and.v at up to. output from a separate 6.8V to V input. The two circuits are completely isolated from each other and can be run simultaneously or independently. The versatile circuit has options for changing the boost diodes for highest efficiency under different output voltage conditions. The feedforward capacitors and noise-reduction capacitors on the Vc pins further increase the parts count on the versatile board, yet they improve the transient response and give the ability to optimize loop compensation under various conditions. This board is designed for applications that require two step-down supplies with up to. load current in a small board space with low cost and low parts count as well as simple circuit design. The high current, onboard, dual monolithic switches eliminate the need for external switches. The use of ceramic capacitors in this circuit not only demonstrates small size and low cost, but the advantage of current-mode control in step-down applications with a simple compensation network and a feedforward capacitor for more rugged stability and excellent transient response. esign files for this circuit board are available. all the LT factory. Table. Typical Performance (T = ) for Small ual Step-own onverter (VOUT=.V and VOUT=.8V) PRMETER VLUE V IN.8V to V VOUT.V V OUT.8V V OUT Load urrent (max) V OUT Load urrent (max) Efficiency 80% at load current (V OUT and V OUT )

2 QUIK STRT GUIE FOR EMONSTRTION IRUIT 9.MHZ UL STEP-OWN / ONVERTER Table. Typical Performance (T = ) for ustomizable ual Step-own onverter (VOUT=.0V and VOUT=.V) Parameter Value V IN 6.8V to V VOUT.0V VOUT.V VOUT Load urrent.(max) VOUT Load urrent.(max) Efficiency 8% at load current (VOUT and VOUT) 00% 00% 90% 90% 80% 80% 70% 70% EFFIIENY 60% 0% 0% 0% = V = 8V = V EFFIIENY 60% 0% 0% 0% = 8V = V = 8V 0% 0% 0% 0% 0% k 0% k.k.k V OUT LO URRENT (m) VOUT LO URRENT = V OUT LO URRENT (m) VOUT LO URRENT = Figure. Typical Efficiency of emo ircuit 9 LT90, Small ual Step-own VOUT=.V, VOUT=.8V Figure. Typical Efficiency of emo ircuit 9 LT90, ustomizable ual Step-own VOUT=.0V, VOUT=.V 00% 00% 90% 90% 80% 80% 70% 70% EFFIIENY 60% 0% 0% 0% = V = 8V = V EFFIIENY 60% 0% 0% 0% = 8V = V = 8V 0% 0% 0% 0% 0% k 0% k.k.k V OUT LO URRENT (m) VOUT LO URRENT = V OUT LO URRENT (m) VOUT LO URRENT = Figure. Typical Efficiency of emo ircuit 9 LT90, Small ual Step-own VOUT=.V, VOUT=.8V Figure. Typical Efficiency of emo ircuit 9 LT90, ustomizable ual Step-own VOUT=.0V, VOUT=.V

3 QUIK STRT GUIE FOR EMONSTRTION IRUIT 9.MHZ UL STEP-OWN / ONVERTER QUIK STRT PROEURE emonstration circuit 9 is easy to set up to evaluate the performance of the LT90. Refer to Figure for proper measurement equipment setup and follow the procedure below: LO. onnect the.8vv or 6.8VV input power supply to the and terminals on the board corresponding to the small, top circuit or the larger, customizable, bottom circuit. Each circuit is powered separately from its own and terminals.. fter all connections are made, turn on input power and verify that the output voltage is either.v and.8v (small, top circuit) or V and.v (larger, bottom circuit) for the circuit to which the input supply is connected. LO. The Run/SS and Power Good functions are optional and their terminals can be left floating (disconnected) if their functions are not being used. onnecting a Run/SS terminal to the terminal will disable the corresponding output. LO LO Figure. Proper Measurement Equipment Setup

4 QUIK STRT GUIE FOR EMONSTRTION IRUIT 9.MHZ UL STEP-OWN / ONVERTER USTOMIZING THE OR The components used in the demonstration circuits are optimized for wide input voltage ranges. Nevertheless, the bandwidths can be increased for more specific input voltages, such as V±0% or V±0%, by changing the V components, the noise filter caps, the feedforward caps, and the output capacitors. The adjustable feedback resistors allow the output voltages to be customized. The boost diodes 8 and on the small circuit are the only boost diode options on that circuit for minimal space considerations. The anode of 8 is connected to Vout (.V). The anode of is connected to Vin (.8V to V) since Vout is.8v and is below.0v. The minimum boost voltage required for the internal power switch is.0v and that can usually be taken directly from a.v output or greater. However, if the output voltage is below.v, in order to maintain high efficiency, the boost diode should get its voltage from either the input (which is less efficient than a greater than.v output) or another source such as the other output on the board (if it is greater than.v). Since there is not space to make these changes in boost diode location on the small circuit, 8 and should always be used (not customized) and Vout should always be.v or greater and Vout can be less than.v. If Vout is.v or greater, the small circuit, with installed connecting to the input, will not be as efficient as it could be if was instead connected to Vout. The larger, versatile circuit has pad placements built-in for customized output voltages of all acceptable levels. and are connected to Vout (V) and Vout (.V) respectively since they are both.v or greater and they provide enough boost to saturate the high-side NPN power switches. However, if either output voltage is customized to less than.v, can be removed and replaced by stuffing with the same part. can be removed and replaced by stuffing with the same part. oth and connect the boost to Vin. dditionally, provides a way to replace with a boost diode that is connected to Vout in case Vout is.v or greater and Vout is less than.v. Make sure that the boost capacitors (7,,, ) have voltage ratings greater than or equal to the output voltage for applications where the boost diode is connected to the output. However, the boost capacitor must have a voltage rating greater than the input voltage whenever the boost diode is connected to the input.

5 EO REV REVISION HISTORY ESRIPTION TE PPROVE > PROTO 0--0 [] MSH- SO L.uH RH8-R R 78.7k ff 6pF R 0uF 6.V VOUT VOUT TP 0 R7 00K TP9 U LT90EFE 6 TP 6.8V to V TP8 IN.7uF X7R V OOST SW 0 SW OOST F Vc PG RUN/SS RUN/SS PG Vc F pF 000pF 7 000pF 8 R6 k R k TP TP TP6 TP7 PG Run/SS Run/SS PG 7 00pF [] VOUT R R.9k ff R8 00K TP0 NOTES: UNLESS OTHERWISE SPEIFIE, [] O NOT STUFF. [] MSH- SO L.uH RH8-R.k 6pF VOUT 0uF 6.V VOUT UNLESS OTHERWISE SPEIFIE IMENSIONS RE IN INHES TOLERNE ON NGLE PLES PLES INTERPRET IM N TOL PER SME Y.M -99 THIR NGLE PROJETION ONTRT NO. PPROVLS TE RWN MEI 0--0 TITLE HEKE PPROVE ENGINEER ESIGNER TEHNOLOGY 60 Mcarthy lvd. Milpitas, 90 Phone: (08)-900 Fax: (08)-007 SH, LT90EFE.MHz UL STEP-OWN / ONVERTER SIZE GE OE WG NO REV ustom 9 O NOT SLE RWING Monday, July, 00 SLE: NONE FILENME: 9-.SN SHEET OF

6 EO REV REVISION HISTORY ESRIPTION TE PPROVE > PROTO MSH- SO L.7uH 008PS-7M R0.k R9 6 0uF 6.V VOUT VOUT U LT90EFE.9k R 00K TP9 TP.8V to V TP8 IN.7uF XR 6V UPS0 UPS OOST SW 0 SW OOST F Vc PG RUN/SS RUN/SS PG Vc F pF 0 00pF R R k k 6 TP PG TP Run/SS TP6 Run/SS TP7 PG 7 NOTES: UNLESS OTHERWISE SPEIFIE, [] O NOT STUFF. MSH- SO L.8uH 008PS-8M R.k R.9k R6 00K VOUT 7 uf 6.V TP0 VOUT UNLESS OTHERWISE SPEIFIE IMENSIONS RE IN INHES TOLERNE ON NGLE PLES PLES INTERPRET IM N TOL PER SME Y.M -99 THIR NGLE PROJETION ONTRT NO. PPROVLS TE RWN MEI 0--0 TITLE HEKE PPROVE ENGINEER ESIGNER TEHNOLOGY 60 Mcarthy lvd. Milpitas, 90 Phone: (08)-900 Fax: (08)-007 SH, LT90EFE.MHz UL STEP-OWN / ONVERTER SIZE GE OE WG NO REV ustom 9 O NOT SLE RWING Monday, July, 00 SLE: NONE FILENME: 9-.SN SHEET OF

7 EO REV REVISION HISTORY ESRIPTION TE PPROVE > RELESE 0//0 [] MSH- SO L.uH RH8-R R 7.0k ff 6pF R 0uF 6.V VOUT VOUT TP 0 R7 00K TP9 U LT90EFE 6 TP 6.8V to V TP8 IN.7uF X7R V OOST SW 0 SW OOST F Vc PG RUN/SS RUN/SS PG Vc F pF 000pF 7 000pF 8 R6 k R k TP TP TP6 TP7 PG Run/SS Run/SS PG 7 00pF [] VOUT R R.9k ff R8 00K TP0 NOTES: UNLESS OTHERWISE SPEIFIE, [] O NOT STUFF. [] MSH- SO L.uH RH8-R.k 6pF VOUT 0uF 6.V VOUT UNLESS OTHERWISE SPEIFIE IMENSIONS RE IN INHES TOLERNE ON NGLE PLES PLES INTERPRET IM N TOL PER SME Y.M -99 THIR NGLE PROJETION ONTRT NO. PPROVLS TE RWN MEI 0--0 TITLE HEKE PPROVE ENGINEER ESIGNER TEHNOLOGY 60 Mcarthy lvd. Milpitas, 90 Phone: (08)-900 Fax: (08)-007 SH, LT90EFE.MHz UL STEP-OWN / ONVERTER SIZE GE OE WG NO REV ustom 9 O NOT SLE RWING Thursday, October, 00 SLE: NONE FILENME: 9-.SN SHEET OF

8 EO REV REVISION HISTORY ESRIPTION TE PPROVE > RELESE 0//0 8 MSH- SO L.7uH 008PS-7M R0.k R9 6 0uF 6.V VOUT VOUT U LT90EFE.9k R 00K TP9 TP.8V to V TP8 IN.7uF XR 6V UPS0 UPS OOST SW 0 SW OOST F Vc PG RUN/SS RUN/SS PG Vc F pF 0 00pF R R k k 6 TP PG TP Run/SS TP6 Run/SS TP7 PG 7 NOTES: UNLESS OTHERWISE SPEIFIE, [] O NOT STUFF. MSH- SO L.8uH 008PS-8M R.0k R.9k R6 00K VOUT 7 uf 6.V TP0 VOUT UNLESS OTHERWISE SPEIFIE IMENSIONS RE IN INHES TOLERNE ON NGLE PLES PLES INTERPRET IM N TOL PER SME Y.M -99 THIR NGLE PROJETION ONTRT NO. PPROVLS TE RWN MEI 0--0 TITLE HEKE PPROVE ENGINEER ESIGNER TEHNOLOGY 60 Mcarthy lvd. Milpitas, 90 Phone: (08)-900 Fax: (08)-007 SH, LT90EFE.MHz UL STEP-OWN / ONVERTER SIZE GE OE WG NO REV ustom 9 O NOT SLE RWING Thursday, October, 00 SLE: NONE FILENME: 9-.SN SHEET OF

9 Linear Technology orporation LT90EFE Parts List 9 Rev 7//00 Item Qty Ref esc Part Number IN P, X7R.7uF V 0% 0 TK X7RE7M IN P, XR.7uF 6V 0% 06 TIYO YUEN EMK6J7KL ff,ff P, NPO 6pF V % 060 VX 06060JT 8,,9,,,,, P, X7R 6V 0% 060 VX 060Y0KT 7, P, XR 0uF 6.V 0% 06 TIYO YUEN JMK6J06ML-T 6,7 P, X7R 000pF 0V % 060 VX 0600JT 7 6,8 P, NPO 00pF 0V % 060 VX 0600JT 8 0 0,,, P, X7R 6V 0% 060 VX 060Y0KT OPTION 9 6 P, XR 0uF 6.V 0% 080 TK 0XR0J06M 0 7 P, XR uf 6.V 0% 0 TK XR0J6M 8 P, X7R 000pF 0V % 00 VX 000JT 0 P, X7R 00pF 0V % 00 VX 00KT 6, P, XR 0V 0% 00 VX 00Z0KT,,8, IOE, MSH- SO ENTRL MSH- 0,, O NOT STUFF OPTION 6 6,7 IOE, 0 SHOTTKY RETIFIER IOES IN. 0 7, IOE, SHOTTKY RETIFIER UPS0 MIROSEMI UPS0 8 L IN,.uH SUMI RH8-R 9 L IN,.uH SUMI RH8-RN 0 L IN,.7uH OILRFT 008PS-7M L IN,.8uH OILRFT 008PS-8M R,R RES,.9k OHMS % /6W 060 R6-9FM R RES, 78.7k OHMS % /6W 060 R6-787FM R RES,.k OHMS % /6W 060 R6-FM R6,R RES, K OHMS % /6W 060 R6-JM 6 R7,R8 RES, 00K OHMS % /6W 060 R6-0JM 7 R,R9 RES,.9k OHMS % /6W 00 R0-9FM 8 R0 RES,.k OHMS % /6W 00 R0-FM 9 R RES,.k OHMS % /6W 00 R0-FM 0 R,R RES, K OHMS % /6W 00 R0-JM R,R6 RES, 00K OHMS % /6W 00 R0-0JM 0 TP-TP0 TURRETS MILL-MX-0- U,U I, LT90EFE UL STEP-OWN / ONVERTER LINER TEH LT90EFE of