Features. Dual Outputs. (See Ordering Information) 5V/3.3V Input Outputs Adjustable Remote Sensing (Vo 1 & Vo 2 ) Standby Function Soft-Start

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1 PT6935 Series - 5V/3.3V-Input Dual Output SLTS9B Revised (9/3/) eatures Dual Outputs (See Ordering Information) 5V/3.3V Input Outputs djustable Remote Sensing (Vo & Vo ) Standby unction Soft-Start Internal Sequencing Short Circuit Protection 3-pin Space-Saving Package Solderable Copper Case Ideal Power Source for DSPs Description The PT6935 Excalibur series of power modules are dual output integrated switching regulators (ISRs) designed to power the latest mixed signal ICs. The dual output provides power for both the digital I/O logic and a DSP core from a single module. Both output voltages are internally sequenced during power-up and power-down to comply with the requirements of the latest DSP chips. Each output is independently adjustable or can be set to at least one alternative bus voltage with a simple pin-strap. The modules are made available in a space-saving solderable case. eatures include an output current limit and short-circuit protection. Ordering Information PT6935o =.5/.8 Volts PT6936o = 3.3/.5 Volts PT6937o = 3.3/.8 Volts PT6938o = 3.3/. Volts PT6939o =.5/. Volts PT Series Suffix (PT34x) Case/Pin Order Package Configuration Suffix Code Vertical N (EL) Horizontal (ELG) SMD C (ELH) (Reference the applicable package code drawing for the dimensions and PC layout) Pin-Out Information Pin unction Vo Sense No Connect 3 STBY 4 V in 5 V in 6 V in 7 GND 8 GND 9 GND GND GND Vo Pin 3 Vo 4 Vo unction 5 Vo 6 Vo djust * 7 No Connect 8 Vo 9 Vo Vo Vo Vo Sense 3 Vo djust * * Vo and Vo can be pin-strapped to another voltage. See application note on output voltage adjustment. Standard pplication Vo Sense STBY Vo Sense 3 8-4,5,6 PT Vo C C C 3 Vo GND GND C = Req d 33µ * electrolytic C = Req d 33µ * electrolytic C3 = Optional µ electrolytic * 3µ for Oscon or low ESR tantalum -see notes

2 PT6935 Series - 5V/3.3V-Input Dual Output General Specifications (Unless otherwise stated, T a =5 C, V in =5V) PT6935 Series Characteristic Symbol Conditions Min Typ Max Units Short Circuit Current I sc Io Io combined 7 Switching requency ƒ o Over V in range 3 3 khz Standby (Pin 3) Referenced to GND (pin 7) Input High Voltage V IH Open () Input Low Voltage V IL..4 V Input Low Current I IL -.5 m Standby Input Current I in standby pin 3 to GND 7 5 m External Output Capacitance C 33 () 3,3 () C 3 33 µ Maximum Operating T a Over V in Range (3) 85 (4) C Temperature Range Storage Temperature T s 5 C Mechanical Shock Per Mil-STD-883D, Method.3 msec, ½ Sine, mounted G s Mechanical Vibration Per Mil-STD-883D, Method 7. 5 (5) G s - Hz, Soldered in a PC board Weight Vertical/Horizontal 6 grams lammability Meets UL 94V-O Notes: () The Standby (pin 3) has an internal pull-up, and if it is left open circuit the module will operate when input power is applied. The open-circuit voltage is less than 5V. Refer to the application notes for interface considerations. () value of 3µ is sufficient if Oscon or low ESR tantalum type capacitors are used. The total combined ESR of all output capacitance at khz must be (greater than) > mω, and (less or equal to) mω. (3) or operating temperatures below C, Cin and Cout must have stable characteristics. Use either tantalum or Oscon capacitors. (4) See Safe Operating rea curves for the specific output voltage combination, or contact the factory for the appropriate derating. (5) Only the case pins on through-hole pin configurations (N & ) must be soldered. or more information see the applicable package outline drawing. Input/Output Capacitors: The PT6935 series requires a 33µ electrolytic capacitor at both the input and output for proper operation (3µ for Oscon or low ESR tantalum). In addition, the input capacitance must be rated for a minimum of.rms ripple current. or transient or dynamic load applications, additional capacitance may be required. Refer to the application notes for more information. Power-up Sequencing and Vo /Vo Loading Power-up Sequencing The PT6935 series of regulators provide two output voltages, Vo and Vo. Each of the output voltage combinations offered by the PT6935 series provides power for both a lowvoltage processor core, and the associated digital support circuitry. In addition, each output is internally sequenced during power-up and power-down to comply with the requirements of most DSP and µp IC s, and their accompanying chipsets. igure shows the typical waveforms of the output voltages, Vo and Vo, from the instance that either input power is applied or the module is enabled via the Standby pin. ollowing a delay of about to 5 milli-secs, the voltages at Vo and Vo rise together until Vo reaches its set-point. Then Vo continues to rise until both output voltages have reached full voltage. igure ; PT6935 Series Power-up V (V/Div) Vo /Vo Loading The output voltages from the PT6935 series regulators are independently regulated. The voltage at Vo is produced by a highly efficient switching regulator. The lower output voltage, Vo, is derived from Vo. The regulation method used for Vo also provides control of this output voltage during power-down. Vo will sink current if the voltage at Vo attempts to fall below it. The load specifications for each model of the PT6935 series gives both a Typical (Typ) and Maximum (Max) load current for each output. or operation within the product s rating, the load currents at Vo and Vo must comply with the following limits:- Io must be less than Io (max). The sum-total current from both outputs (Io Io ) must not exceed Io (max). In the case that either Vo or Vo are adjusted to some other value than the default output voltage, the absolute maximum load current for Io must be revised to comply with the following equation. V (V/Div) Io (max) =.5 Vo Vo dc Vstby (V/Div) Consult the specification table for each model of the series for the actual numeric values. HORIZ SCLE: 5ms/Div

3 PT6935 mp 5V/3.3V-Input Dual Output PT6935 Performance Specifications (Unless otherwise stated, T a =5 C, V in =5V, C =33µ, C =33µ, Io =Io typ, and Io =Io typ) PT6935 (.5V/.8V) Characteristic Symbol Conditions Min Typ Max Units Output Current Io T a =5 C, natural convection Vo (.5V). (i) 7 (ii) 9.5 (iii) Io Vo (.8V).5 (ii) 3.5 (iii) Io T a = C, LM airflow Vo (.5V). (i) 7 (ii) (iii) Io Vo (.8V).5 (ii) 3.5 (iii) Input Voltage Range V in Over I o Range VDC Set Point Voltage Tolerance V o tol Vo ±±38 Vo ±9 ± 7 Temperature Variation Reg temp >T a > 85 C ±.5 %V o Line Regulation Reg line Over V in range Vo ±5 ± Vo ± ±5 Load Regulation Reg load Over I o range Vo ±5 ± Vo ±5 ± ± Total Output Voltage Variation V otot Includes set-point, line, load, Vo ±34 >T a > 85 C Vo 5 Efficiency η 79 % V o Ripple (pk-pk) V r MHz bandwidth Vo 35 Vo pp 35 Transient Response t tr /µs load step, % to % I otyp µs V V o over/undershoot Vo ± tr Vo ± Notes: (i) Io (min) current of. can be divided between both outputs, Vo or Vo. The module will operate at no load with reduced specifications. (ii) The typical current is that which can be drawn simultaneously from both outputs under the stated operating conditions. (iii) The sum of Io and Io must be less than Io max, and Io must be less than Io max. PT6935 Typical Characteristics 85 Efficiency vs Io (See Note ) Power Dissipation vs Io (See Note ) 8 8 Efficiency - % V Pd - Watts V Io () [ Io fixed at Io (typ) ] Io () [ Io fixed at Io (typ) ] Vo Output Ripple vs Io (See Note ) 9 Safe Operating rea, V in =5V (See Note B) 8 Ripple V mbient Temperature ( C) irflow LM LM LM Nat conv Io () [ Io fixed at Io (typ) ] Iout () Note : Characteristic data has been developed from actual products tested at 5 C. This data is considered typical data for the Converter. Note B: SO curves represent the conditions at which internal components are at or below the manufacturer s maximum operating temperatures

4 PT6936 mp 5V/3.3V-Input Dual Output PT6936 Performance Specifications (Unless otherwise stated, T a =5 C, V in =5V, C =33µ, C =33µ, Io =Io typ, and Io =Io typ) PT6936 (3.3V/.5V) Characteristic Symbol Conditions Min Typ Max Units Output Current Io T a =5 C, natural convection Vo (3.3V). (i) 8 (ii) (iii) Io Vo (.5V) 3 (ii) 3 (iii) Io T a = C, LM airflow Vo (3.3V). (i) 8 (ii) (iii) Io Vo (.5V) 3 (ii) 3 (iii) Input Voltage Range V in Over I o Range VDC Set Point Voltage Tolerance V o tol Vo ±6 ± Vo ±±38 Temperature Variation Reg temp >T a > 85 C ±.5 %V o Line Regulation Reg line Over V in range Vo ±5 ± Vo ± ±5 Load Regulation Reg load Over I o range Vo ±5 ± Vo ±5 ± ± Total Output Voltage Variation V otot Includes set-point, line, load, Vo 9 >T a > 85 C Vo ±34 Efficiency η 8 % V o Ripple (pk-pk) V r MHz bandwidth Vo 35 Vo 35 pp Transient Response t tr /µs load step, % to % I o typ µs V V o over/undershoot Vo ± tr Vo ± Notes: (i) Io (min) current of. can be divided between both outputs, Vo or Vo. The module will operate at no load with reduced specifications. (ii) The typical current is that which can be drawn simultaneously from both outputs under the stated operating conditions. (iii) The sum of Io and Io must be less than Io max, and Io must be less than Io max. PT6936 Typical Characteristics 85 Efficiency vs Io (See Note ) Power Dissipation vs Io (See Note ) 8 8 Efficiency - % 75 Pd - Watts Io out () [ Io fixed at Io (typ) ] Io out () [ Io fixed at Io (typ) ] Vo Output Ripple vs Io (See Note ) 9 Safe Operating rea, V in =5V (See Note B) 8 Ripple - 3 mbient Temperature ( C) irflow LM LM LM Nat conv Io out () [ Io fixed at Io (typ) ] Io () [ Io fixed at Io (typ) ] Note : Characteristic data has been developed from actual products tested at 5 C. This data is considered typical data for the Converter. Note B: SO curves represent the conditions at which internal components are at or below the manufacturer s maximum operating temperatures

5 PT6937 mp 5V/3.3V-Input Dual Output PT6937 Performance Specifications (Unless otherwise stated, T a =5 C, V in =5V, C =33µ, C =33µ, Io =Io typ, and Io =Io typ) PT6937 (3.3V/.8V) Characteristic Symbol Conditions Min Typ Max Units Output Current Io T a =5 C, natural convection Vo (3.3V). (i) 8 (ii) (iii) Io Vo (.8V) (ii).5 (iii) Io T a = C, LM airflow Vo (3.3V). (i) 8 (ii) (iii) Io Vo (.8V) (ii).5 (iii) Input Voltage Range V in Over I o Range VDC ± Set Point Voltage Tolerance V o tol Vo ±6 ± Vo ±9 7 Temperature Variation Reg temp >T a > 85 C ±.5 %V o Line Regulation Reg line Over V in range Vo ±5 ± Vo ± ±5 Load Regulation Reg load Over I o range Vo ±5 ± Vo ±5 ± ± ± Total Output Voltage Variation V otot Includes set-point, line, load, Vo 9 >T a > 85 C Vo 5 Efficiency η 8 % V o Ripple (pk-pk) V r MHz bandwidth Vo 35 Vo 35 pp Transient Response t tr /µs load step, % to % I o typ µs V V o over/undershoot Vo ± tr Vo ± Notes: (i) Io (min) current of. can be divided between both outputs, Vo or Vo. The module will operate at no load with reduced specifications. (ii) The typical current is that which can be drawn simultaneously from both outputs under the stated operating conditions. (iii) The sum of Io and Io must be less than Io max, and Io must be less than Io max. PT6937 Typical Characteristics 85 Efficiency vs Io (See Note ) Power Dissipation vs Io (See Note ) Efficiency - % 65 Pd - Watts Io () [ Io fixed at Io (typ) ] Io () [ Io fixed at Io (typ) ] Vo Output Ripple vs Io (See Note ) 9 Safe Operating rea, V in =5V (See Note B) 8 Ripple - 3 mbient Temperature ( C) irflow LM LM LM Nat conv Io () [ Io fixed at Io (typ) ] Io () [ Io fixed at Io (typ) ] Note : Characteristic data has been developed from actual products tested at 5 C. This data is considered typical data for the Converter. Note B: SO curves represent the conditions at which internal components are at or below the manufacturer s maximum operating temperatures

6 PT6938 mp 5V/3.3V-Input Dual Output PT6938 Performance Specifications (Unless otherwise stated, T a =5 C, V in =5V, C =33µ, C =33µ, Io =Io typ, and Io =Io typ) PT6938 (3.3V/.V) Characteristic Symbol Conditions Min Typ Max Units Output Current Io T a =5 C, natural convection Vo (3.3V). (i) 7 (ii) 8.6 (iii) Io Vo (.V).6 (ii).6 (iii) Io T a = C, LM airflow Vo (3.3V). (i) 7 (ii) 8.6 (iii) Io Vo (.V).6 (ii).6 (iii) Input Voltage Range V in Over I o Range VDC Set Point Voltage Tolerance V o tol Vo ±6 ± Vo ±6 ±8 Temperature Variation Reg temp >T a > 85 C ±.5 %V o Line Regulation Reg line Over V in range Vo ±5 ± Vo ± ±5 Load Regulation Reg load Over I o range Vo ±5 ± Vo ±5 ± ± Total Output Voltage Variation V otot Includes set-point, line, load, Vo 9 >T a > 85 C Vo ±9 Efficiency η 79 % V o Ripple (pk-pk) V r MHz bandwidth Vo 35 Vo 35 pp Transient Response t tr /µs load step, % to % I o typ µs V V o over/undershoot Vo ± tr Vo ± Notes: (i) Io (min) current of. can be divided between both outputs, Vo or Vo. The module will operate at no load with reduced specifications. (ii) The typical current is that which can be drawn simultaneously from both outputs under the stated operating conditions. (iii) The sum of Io and Io must be less than Io max, and Io must be less than Io max. PT6938 Typical Characteristics 85 Efficiency vs Io (See Note ) Power Dissipation vs Io (See Note ) 8 8 Efficiency - % 75 Pd - Watts Io () [ Io fixed at Io (typ) ] Io () [ Io fixed at Io (typ) ] Vo Output Ripple vs Io (See Note ) 9 Safe Operating rea, V in =5V (See Note B) 8 Ripple - 3 mbient Temperature ( C) irflow LM LM LM Nat conv Io () [ Io fixed at Io (typ) ] Io () [ Io fixed at Io (typ) ] Note : Characteristic data has been developed from actual products tested at 5 C. This data is considered typical data for the Converter. Note B: SO curves represent the conditions at which internal components are at or below the manufacturer s maximum operating temperatures

7 PT6939 mp 5V/3.3V-Input Dual Output PT6939 Performance Specifications (Unless otherwise stated, T a =5 C, V in =5V, C =33µ, C =33µ, Io =Io typ, and Io =Io typ) PT6939 (.5V/.V) Characteristic Symbol Conditions Min Typ Max Units Output Current Io T a =5 C, natural convection Vo (.5V). (i) 7 (ii) 9 (iii) Io Vo (.V) (ii). (iii) Io T a = C, LM airflow Vo (.5V). (i) 7 (ii) 9 (iii) Io Vo (.V) (ii). (iii) Input Voltage Range V in Over I o Range VDC Set Point Voltage Tolerance V o tol Vo ±±38 Vo ±6 ±8 Temperature Variation Reg temp >T a > 85 C ±.5 %V o Line Regulation Reg line Over V in range Vo ±5 ± Vo ± ±5 Load Regulation Reg load Over I o range Vo ±5 ± Vo ±5 ± Total Output Voltage Variation V otot Includes set-point, line, load, Vo ±34 >T a > 85 C Vo ±9 Efficiency η 75 % V o Ripple (pk-pk) V r MHz bandwidth Vo 35 Vo 35 pp Transient Response t tr /µs load step, % to % I o typ µs V V o over/undershoot Vo ± tr Vo ± Notes: (i) Io (min) current of. can be divided between both outputs, Vo or Vo. The module will operate at no load with reduced specifications. (ii) The typical current is that which can be drawn simultaneously from both outputs under the stated operating conditions. (iii) The sum of Io and Io must be less than Io max, and Io must be less than Io max. PT6939 Typical Characteristics 85 Efficiency vs Io (See Note ) Power Dissipation vs Io (See Note ) 8 8 Efficiency - % V 5V Pd - Watts 6 4 5V 3.3V Io () [ Io fixed at Io (typ) ] Io () [ Io fixed at Io (typ) ] Vo Output Ripple vs Io (See Note ) 9 Safe Operating rea, V in =5V (See Note B) 8 Ripple - 3 5V 3.3V mbient Temperature ( C) irflow LM LM LM Nat conv Io () [ Io fixed at Io (typ) ] Io () [ Io fixed at Io (typ) ] Note : Characteristic data has been developed from actual products tested at 5 C. This data is considered typical data for the Converter. Note B: SO curves represent the conditions at which internal components are at or below the manufacturer s maximum operating temperatures

8 pplication Notes PT6935 Series Capacitor Recommendations for the Dual-Output PT6935 Regulator Series Input Capacitors: The recommended input capacitance is determined by. ampere minimum ripple current rating and 33µ minimum capacitance (3µ for Oscon or low ESR tantalum). Ripple current and <mω equivalent series resistance (ESR) values are the major considerations, along with temperature, when designing with different types of capacitors. Tantalum capacitors have a recommended minimum voltage rating of the maximum DC voltage C ripple. This is necessary to insure reliability for input voltage bus applications Output Capacitors: C (Required), C 3 (Optional) The ESR of the required capacitor (C ) must not be greater than mω. Electrolytic capacitors have poor ripple performance at frequencies greater than khz but excellent low frequency transient response. bove the ripple frequency, ceramic capacitors are necessary to improve the transient response and reduce any high frequency noise components apparent during higher current excursions. Preferred low ESR type capacitor part numbers are identified in Table. The optional µ capacitor (C 3 ) for V out can have an ESR of up to mω for optimum performance and ripple reduction. (Note: Vendor part numbers for the optional capacitor, C 3, are not identified in the table. Use the same series selected for C ) Tantalum Capacitors Tantalum type capacitors can be used for the output but only the VX TPS series, Sprague 593D/594/595 series or Kemet T495/T series. These capacitors are recommended over many other tantalum types due to their higher rated surge, power dissipation, and ripple current capability. s a caution the TJ series by VX is not recommended. This series has considerably higher ESR, reduced power dissipation, and lower ripple current capability. The TJ series is less reliable than the VX TPS series when determining power dissipation capability. Tantalum or Oscon types are recommended for applications where ambient temperatures fall below C. Capacitor Table Table identifies the characteristics of capacitors from a number of vendors with acceptable ESR and ripple current (rms) ratings. The number of capacitors required at both the input and output buses is identified for each capacitor type. This is not an extensive capacitor list. Capacitors from other vendors are available with comparable specifications. Those listed are for guidance. The RMS ripple current rating and ESR (Equivalent Series Resistance at khz) are critical parameters necessary to insure both optimum regulator performance and long capacitor life. Table : Input/Output Capacitors Capacitor Vendor/ Component Series Working V oltage Value(µ ) Capacitor (ESR) Equivalent Series Resistance Characteristics 85 C Maximum Ripple Current(Irms) Physical Size(mm) Quantity Input Bus Output Bus Vendor Number Panasonic C 5V 35V 35V 5µ 39µ 33µ.65Ω.65Ω.7Ω 5m 5m 555m.5x5.5x5 8x.5 N/R EEUCE56S EEUCV39S EEUCC33 United Chemi-Con LXV/S/ LXZ 6V 35V V V 33µ 4µ 33µ µ.ω.5ω.5ω.3 Ω 555m m 3m 3m 8x x x.5 x.5 N/R LXZ6VB33M8XLL LXZ35VB47MXLL S33M SM Nichicon PL/ PM 35V 35V V 5µ 33µ 4µ.48Ω.65 Ω.46Ω 3m m 4m 6x5.5x5 8x5 UPLV56MHH6 UPLV33MHH6 UPMH47MHH6 Panasonic C (Surface Mtg) V 35V 6V µ 33µ 33µ.43Ω.65Ω.Ω 5m 5m 6m x6.5.5x6 x. N/R EEVCLQ EEVCV33LQ EEVCC33P Oscon- SS SV V V V 33µ 33µ µ.5ω.5ω.4 Ω >3m >38m 3m.x.5.3x.3.3x.3 SS33M SV3M SVM SV= Surface Mount VX Tantalum TPS V V V 33µ 33µ µ. Ω. Ω.95Ω >m >3m >m 7.3Lx 4.3Wx 4.H TPSV337MR TPSV337MR TPSV7M5R Kemet T/ T495 V V 33µ µ.33ω.7ω =.35Ω m >m 7.3Lx5.7W x 4.H TX337MS T495X7MS Sprague 594D V V 33µ µ.45ω.65ω 3m >m 7.3Lx 6.Wx 4.H 4D337XRT 594D7XDT N/R Not recommended. The voltage rating does not meet the minimum operating limits.

9 pplication Notes PT6935 Series djusting the Output Voltage of the PT6935 Dual Output Voltage ISRs Each output voltage from the PT6935 series of ISRs can be independantly adjusted higher or lower than the factory trimmed pre-set voltage. The voltages, Vo and Vo may each be adjusted either up or down using a single external resistor. Table gives the adjustment range for both Vo and Vo for each model in the series as V a (min) and V a (max). Note that Vo must always be lower than Vo. Vo djust Up: To increase the output, add a resistor R4 between pin 6 (V djust) and pins 7- (GND). Vo djust Down: dd a resistor (R3), between pin 6 (Vo djust) and pin (Vo Sense). Vo djust Up: dd a resistor R between pin 3 (Vo djust) and pins 7- (GND). Vo djust Down: dd a resistor (R) between pin 3 (Vo djust) and pin (Vo Sense). Refer to igure and Table for both the placement and value of the required resistor. Notes:. Use only a single % resistor in either the (R3) or R4 location to adjust Vo, and in the (R) or R location to adjust Vo. Place the resistor as close to the ISR as possible.. Vo must always be at least.v lower than Vo. 3. Both the Vo and Vo may be adjusted down to an alternative bus voltage by making, (R3) or (R) respectively, a zero ohm link. Refer to the Table footnotes for guidance. 4. djusting the Vo output voltage of either the PT6935 (.5V/.8V model) or PT6939 (.5V/.V) higher than the factory pre-trimmed output voltage, may increase the minimum input voltage specified for the part. These models must comply with the following requirements. PT6935/PT6939: V in (min) =(V a.6)v or 3.V, whichever is greater. 5. Never connect capacitors to either the Vo djust or Vo djust pins. ny capacitance added to these control pins will affect the stability of the respective regulated output. 6. djusting either voltage (Vo or Vo ) may increase the power dissipation in the regulator, and change the maximum current available at either output. Consult the note on p. of the data sheet regarding Vo /Vo loading. The adjust up and adjust down resistor values can also be calculated using the following formulas. Be sure to select the correct formula parameter from Table for the output and model being adjusted. (R ) or (R 3 ) = (R ) or (R 4 ) = (V a V r ) Rs kω V o V a V r R s kω V a V o Where: V o = Original output voltage, (Vo or Vo ) V a = djusted output voltage V r = The reference voltage from Table R s = The series resistance from Table igure 4,5,6 Vin PT6935 Vo (sns) Vo (sns) Vo Vo Vo Vo C STBY 3 GND 7 - Vo (adj) 3 Vo (adj) (R3) dj Down 6 (R) C C 3 L O D L O D R4 djust Up R COM COM djust Vo djust Vo

10 pplication Notes PT6935 Series Table DJUSTMENT RNGE ND ORMUL PRMETERS Vo Bus Vo Bus () Series Pt # PT6935/39 PT6936/37/38 PT6938/39 PT6935/37 PT6936 dj. Resistor (R3)/R4 (R3)/R4 (R)/R (R)/R (R)/R V o(nom).5v 3.3V.V.8V.5V Va(min).8V *.5V *.V.5V.8V Va(max) 3.6V (4) 3.6V.5V #.4V 3. Vr.7V.7V.65V.V.V R s (kω) Ref. Note 3: * (R3) = Zero-ohm link (R) = Zero-ohm link # (R) = Zero-ohm link Table DJUSTMENT RESISTOR VLUES Vo Bus Series Pt # PT6935/39 PT6936/37/38 dj. Resistor (R3)/R4 (R3)/R4 V o (nom).5v 3.3V V a(req d).8 (.).85 (.4)kΩ.9 (3.)kΩ.95 (4.9)kΩ. (7.)kΩ.5 (9.8)kΩ. (3.3)kΩ. (3.5)kΩ.3 (44.)kΩ.4 (6.)kΩ.5 (.)kω.6.kω (3.6)kΩ.7 56.kΩ (8.4)kΩ kΩ (5.)kΩ.9 4.3kΩ (5.4)kΩ kΩ (4.3)kΩ kΩ (76.)kΩ 3..6kΩ kΩ (78.)kΩ kΩ.k kΩ 48.k kΩ 6.9k R /R 3 = (Blue), R /R 4 = Black Vo Bus Series Pt # PT6938/39 PT6935/37 PT6936 dj. Resistor (R)/R (R)/R (R)/R V o (nom).v.8v.5v V a(req d). (.)kω.5 (9.)kΩ. (8.8)kΩ.5 (87.5)kΩ..5.5kΩ.3 4.kΩ.35.8kΩ.4.6kΩ kΩ.5.kΩ (.)kω.55 (5.)kΩ.6 (3.)kΩ.65 (6.4)kΩ.7 (53.)kΩ.75 (33.)kΩ.8 (.)kω kΩ (.6)kΩ.9 83.kΩ (3.5)kΩ kΩ (5.8)kΩ. 33.kΩ (8.5)kΩ.5 3.kΩ (.8)kΩ. 6.4kΩ (6.)kΩ. 8.kΩ (8.5)kΩ.3 3.kΩ (53.5)kΩ.4.kΩ (9.)kΩ kΩ kΩ.8.8kΩ.9 3.5kΩ kΩ

11 pplication Notes PT6935 Series Using the Standby unction on the PT6935 Series of Dual-Output Voltage Regulators Both output voltages of the 3-pin PT6935 dual-output converter may be disabled using the regulator s Standby function. This function may be used in applications that require power-up/shutdown sequencing, or wherever there is a requirement to control the output voltage On/Off status with external circuitry. The standby function is provided by the STBY* control (pin 3). If pin 3 is left open-circuit the regulator operates normally, and provides a regulated output at both Vo (pins 5) and Vo (pins 8 ) whenever a valid supply voltage is applied to V in (pins 4, 5, & 6) with respect to GND (pins 7-). If a low voltage is then applied to pin-3 both regulator outputs will be simultaneously disabled and the input current drawn by the ISR will drop to a typical value of 7m. The standby control may also be used to hold-off both regulator outputs during the period that input power is applied. The standby pin is ideally controlled using an open-collector (or open-drain) discrete transistor (See igure ). The open-circuit voltage is typically.6v. Table gives the circuit parameters for this control input. Table Standby Control Parameters, Parameter Min Max Enable (V IH) Open circuit Disable (V IL).V.4V V STBY (open circuit).6v 5V I STBY (I IL ).5m igure Vo 4, 5, 6 V V in IN PT Vo Vo Inhibit COM Turn-On Time: Turning Q in igure off removes the lowvoltage signal at pin 3 and enables the PT6935 regulator. ollowing a delay of about 5ms, Vo and Vo rise together until the lower voltage, Vo, reaches its set output. Vo continues to rise until both outputs reach full regulation voltage. The total power-up time is less than 3ms, and is relatively independent of load, temperature, and output capacitance. igure shows waveforms of the output voltages, Vo and Vo, for a PT6937 (3.3V/.8V). The turn-off of Q corresponds to the rise in V STBY. The waveforms were measured with a 5V input voltage, and with resistive loads of 4.5 and.9 at the Vo and Vo outputs respectively. igure C Q BSS38 STBY 3 GND 7 - Vo (sns) Vo (adj) 3 Vo (sns) Vo Vo (adj) C C 3 COM Notes:. The standby control input is Not compatible with TTL or other devices that incorporate a totem-pole output drive. Use only a true open-collector device, preferably a discrete bipolar transistor (or MOSET). To ensure the regulator output is disabled, the control pin must be pulled to less than.4vdc with a low-level.5m sink to ground. The standby control input requires no external pull-up resistor. The open-circuit voltage of the STBY* pin is typically.6v. 3. When the regulator output is disabled the current drawn from the input source is typically reduced to 7m. HORIZ SCLE: 5ms/Div V (V/Div) V (V/Div) Vstby (V/Div)

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