STEP-DOWN SWITCHING VOLTAGE REGULATOR IN HERMETIC ISOLATED PACKAGE

Transcription

1 OM7 Series OMH7 Series STEP-DOWN SWITCHING VOLTAGE REGULATOR IN HERMETIC ISOLATED PACKAGE. Amp, V, V, V And Adjustable Voltage Versions In MO-78 Metal Package FEATURES Similar To Industry Standard LM7 Available in V, V, V, And Adjustable Versions. Amp Wide Input Voltage Range, V to 6V 3 khz Fixed Frequency Internal Oscillator High Efficiency Hermetic Metal Packages DESCRIPTION This series of regulators are monolithic integrated circuits designed for the active functions of a step down, buck or buck/boost regulator. It requires only four readily available standard components to complete the DC to DC converter design at Amp. Current limiting and thermal shutdown features fully protect the device against overstress. The hermetic package is ideally suited for those critical environments requiring high reliability over a wide operating temperature range. ABSOLUTE MAXIMUM T C = C Maximum Supply Voltage OM7... V OMH V Pin Input Voltage V V V IN Voltage To Ground (Steady State)...- V Power Dissipation...Internally Limited Operating Temperature Range...- C to C Storage Temperature Range...-6 C to C Thermal Resistance, Rq JC... C/W Lead Soldering Temperature ( seconds)...6 C INPUT Feedback BLOCK DIAGRAM REG Internal Resistors For Fixed Options Only E/A - REF PWM - DRV OSC RESET PROTECTION GND R - 33

2 OM7 OMH7 Series ELECTRICAL CHARACTERISTICS Unless otherwise specified V IN = V for V and ADJ options; V for V; and 3V for V models; V OUT = V for ADJ, I O =.A to A, T J = C. V IN rated = V, and 6V for OMH Series. Test Conditions Limits Parameter Symbol V IN I O T J MIN. TYP. MAX. UNIT OM7- V O.A.9. Over Temp..8. V 8V to V IN Rated.8. OM7- V O.A.88. Over Temp...8 V V to V IN Rated.6.36 OM7- V O.A.8. 8V to V IN Rated Over Temp...6 V.. Feedback Voltage V FB.A.7.3 V OUT = V 8V to V IN Rated Over Temp V OM7-A.. Feedback Bias Current I B V.A na Over Temp. Efficiency/Option n A 8 V 88 % 8V 9 A V O = V V 8 Switching Frequency F SX 7 8 khz Over Temp. 3 6 Saturation Voltage () V SAT. A Over Temp..9. V Maximum Duty Cycle (On) (3) DC % Current Limit () Peak Current A Peak Current I CL T on 3µsec Over Temp Leakage Current() = V I L V IN Rated ma = -V 7. 3 Quiescent Current () I O ma Over Temp. Standby Quiescent I STBY µa Current (On/Off Pin = V) Over Temp. On/Off Pin Logic V IH Input Level. V V OUT = V Over Temp... V OUT = Option V IL. V Over Temp...8 On/Off Input Current On/Off = V (Off) I IH.A 3 µa On/Off = V (Off) I IL Notes: Over Temperature: - C to C. () sourcing current - resistive load, no inductor or capacitor. () Feedback = V O.V. (3) Feedback = V. () Not all parameters are % tested during production. Consult the factory for more information. - 3

3 Dropout Voltage OPERATIONAL DATA Minimum Operating Voltage OM7 OMH7 Series V IN - V OUT (V).... V OUT = % R IND =.Ω I O = A Input Voltage (V) I O = ma V OUT =.3V. I O = ma Normalized Feedback Voltage (mv) - Line Regulation (Adjustable Version Only) 7 Normalized to V IN = V I O = ma, V OUT = V T J = C Feedback Current (na) - - Feedback Pin Current Input Voltage (V) Normalized Feedback Voltage (mv) - - Normalized Feedback Voltage (Adjustable Version Only) V IN = V I O = ma Normalized to T J = C Feedback Voltage Change (mv) - - Feedback Voltage vs Duty Cycle (Adjustable Version Only) V IN = 7V I O = ma V IN = V Duty Cycle (%) - 3

4 OM7 OMH7 Series Supply Current vs. Duty Cycle OPERATIONAL DATA Supply Current Supply Current (ma) V IN = 7V I O = ma V IN = V Supply Current (ma) I LOAD = ma Measured At Ground Pin T J = C, V OUT = V I LOAD = A 6 8 Duty Cycle (%) Input Voltage (V) Current Limit Switch Saturation Voltage 3.. Current (A).. V IN = V Saturation Voltage (V) T J = - C T J = C T J = C Switch Current (A) Efficiency Standby Quiescent Current Efficiency (%) A V OUT = V ma ma V OUT = 3V A Standby Quiescent Current (µa) V IN = V V = V V IN = V Input Voltage (V)

5 OM7 OMH7 Series Catch Diode If the output must be capable of a sustained short, the I F rating must be above 3A. The use of an ultra fast diode with soft recovery characteristics or a Schottky will be adequate. The major impact on Schottky versus an ultra fast is efficiency. Schottkys will provide approximately % to % improvement for output voltage below V, whereas above V the difference will become less significant. Breakdown rating must be in excess of V IN for margin. Input Capacitor The value shown will be adequate for most applications. Ripple voltage at the switching frequency is caused by the input capacitor supplying load current during the on time of the power switch. The use of a low ESR switching type capacitor will minimize ripple to an acceptable level. Layout Use short connections with a central point ground to prevent improper operation caused by stray inductance and ground loops. Capacitor Ripple voltage on V OUT is directly related to the value of and the internal resistance ESR of. noise can be lowered by increasing or by selecting a capacitor with a lower ESR. ESR must be approximately.7 or above to maintain stability, otherwise raise value of. BUCK MODE FIXED VOLTAGE 68µF REC ON/ E/A - PWM - DRV 33µH L 3 REF OSC RESET PROTECTION 3A 33µF 68µF REC ON/ BUCK MODE ADJUSTABLE VOLTAGE E/A - PWM - DRV 33µH L 3 REF OSC RESET PROTECTION 3A 33µF K R R The above fixed and adjustable voltage selections will be adequate for most applications for output currents from ma to.a. Applications of V OUT below V or above V may require component adjustment for maximum performance; please contact factory for application assistance. - 37

6 OM7 OMH7 Series Switching Spikes Switching spikes will also occur due to distributive capacitance across turns of the inductor when combined with output capacitor series inductance (ESL). Reduction to a level at or below the switching ripple can be achieved by using a post filter, as shown in the Switching Spike Reduction Schematic. SWITCHING SPIKE REDUCTION L V IN OUTPUT µh DC INPUT 3 µf TANT V OUT GND TYPICAL APPLICATION TURN-ON DELAY WITH SPIKE FILTER V IN.7µF to 3.µF 3 FEEDBACK OUTPUT Regulated k.k N9 Spike filter reduces input noise, causing false triggering of delay. - 38

7 OM7 OMH7 Series TYPICAL APPLICATIONS Unregulated DC Input ON V Shutdown Input TTL, CMOS, etc. TYPICAL BUCK SHUTDOWN FEEDBACK V IN OUTPUT L 3 GND Regulated V ON FEEDBACK Unregulated DC Input V IN OUTPUT L k 3 GND Shutdown Input k k Regulated TURN-ON DELAY V IN.7µF to 3.µF 3 OUTPUT Regulated k N9 Circuit allows for to be fully charged before start-up, provides to supply hi-peak current instead of input supply. - 39

8 OM7 OMH7 Series TYPICAL APPLICATIONS INVERTING BUCK/BOOST SHUTDOWN Unregulated DC Input V IN FEEDBACK OUTPUT L k 7k 3 GND ON 7k V Shutdown Input 33k 7k - Regulated V V ON Shutdown Input k FEEDBACK Unregulated DC Input V IN OUTPUT L V 7k 3 GND - Regulated UNDER VOLTAGE LOCKOUT Unregulated DC Input R K Z k V IN 3 FEEDBACK OUTPUT GND Regulated Q R k Regulator will be off until a V IN set point is reached. V O(ON) V Z 3V BE Q -

9 OM7 OMH7 Series TYPICAL APPLICATIONS INVERTING BUCK/BOOST V 7µF REC ON/ E/A - PWM - DRV µh L 3 REF OSC RESET PROTECTION 3A 33µF V TO ma ma V 7µF REC ON/ E/A - PWM - DRV 7µH L 3 REF OSC RESET PROTECTION 3A µf COMMON V TO ma ma Inverting buck/boost operation is a different topology of operation than buck. This difference reduces the output current capability of the device, in that the inductor must supply all of the load current during the time the power switch is off: Maximum output current is approximately: I ( œv O œ/ V IN ) Component requirement stress is very similar to the buck with a few exceptions: Catch diode breakdown V BR must be greater than V IN œv OUT œ Input capacitor is larger due to the increased peak current during switch turn on. Power dissipation of the OM7 is approximately: P [œv O œ/ (œv O œ V IN )] I O ( œv O œ/ V IN ) Please contact factory for additional assistance when using the buck/boost topology. -

10 OM7 OMH7 Series MECHANICAL OUTLINE PIN CONNECTION MO-78 PACKAGE MAX TYP..3.. TYP. 3 Pin : V IN Pin : OUT Pin 3: GND Pin : Feedback Pin : Z-TAB PACKAGE TYP.. TYP.. TYP.. PLCS TYP MAX. 3 Pin : V IN Pin : OUT Pin 3: GND Pin : Feedback Pin : ORDERING INFORMATION EXAMPLE: P/N OM 7 - SCM = Volt, C Package With Screening PART NUMBER VOLTAGE LEVEL CASE STYLE SCREENING OM7 = Volt SC = MO-78 Add M OMH7 = Volt SCZ = Z-Tab for 883 = Volt Both Packages screening A = Adjustable are Isolated See section 3. Crawford Street, Leominster, MA 3 USA (8) FAX (8) 37-6