SWITCHING REGULATOR OUTPUT CURRENT 5.1V OUTPUT VOLTAGE RANGE DUTY

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SWITCHING REGULATOR OUTPUT CURRENT 5.1V OUTPUT VOLTAGE RANGE DUTY

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L4970A
SWITCHING REGULATOR
OUTPUT CURRENT 5.1V OUTPUT VOLTAGE RANGE DUTY CYCLE RANGE INTERNAL FEED-FORWARD LINE REGULATION INTERNAL CURRENT LIMITING PRECISE 5.1V CHIP REFERENCE RESET POWER FAIL FUNCTIONS SOFT START INPUT/OUTPUT SYNC UNDER VOLTAGE LOCK WITH HYSTERETIC TURN-ON LATCH SINGLE PULSE PERIOD VERY HIGH EFFICIENCY SWITCHING FREQUENCY 500KHz THERMAL SHUTDOWN CONTINUOUS MODE OPERATION DESCRIPTION L4970A stepdown monolithic power switching regulator delivering voltage variable from 40V. BLOCK DIAGRAM
MULTIPOWER TECHNOLOGY
Multiwatt15V ORDERING NUMBER: L4970A
Realized with mixed technology, device uses DMOS output transistor obtain very high efficiency very fast switching times. Features L4970A include reset power fail microprocessors, feed forward line regulation, soft start, limiting current thermal protection. device mounted 15-lead multiwatt plastic power package requires external components. Efficient operation switching frequencies 500KHz allows reduction size cost external filter components.
June 2000
1/21
This advanced information product development undergoing evaluation. Details subject change without notice.
L4970A
ABSOLUTE MAXIMUM RATINGS
Symbol V10, V11, Ptot Tstg Input Voltage Input Operating Voltage Output Voltage Output Peak Voltage 0.1µs 200KHz Maximum Output Current Bootstrap Voltage Bootstrap Operating Voltage Input Voltage Pins Reset Output Voltage Reset Output Sink Current Input Voltage Reset Delay Sink Current Error Amplifier Output Sink Current Soft Start Sink Current Total Power Dissipation Tcase 120°C Junction Storage Temperature Parameter Value Internally Limited Unit
CONNECTION (Top view)
THERMAL DATA
Symbol j-case j-amb Parameter Thermal Resistance Junction-case Thermal Resistance Junction-ambient Value Unit °C/W °C/W
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L4970A
FUNCTIONS
Name OSCILLATOR OSCILLATOR RESET INPUT Function Rosc. External resistor connected ground determines constant charging current Cosc. Cosc. External capacitor connected ground determines (with Rosc) switching frequency. Input Power Fail Circuit. threshold 5.1V. connected divider input power fail function. must connected external resistor when power fail signal required. Open Collector Reset/power Fail Signal Output. This output high when supply output voltages safe. capacitor connected between this terminal ground determines reset signal delay time. Cboot capacitor connected between this terminal output allows drive properly internal D-MOS transistor. Regulator Output. Common Ground Terminal Unregulated Input Voltage. series network connected between this terminal ground determines regulation loop gain characteristics. Feedback Terminal Regulation Loop. output connected directly this terminal 5.1V operation; connected divider higher voltages. Soft Start Time Constant. capacitor connected between sterminal ground define soft start time constant. Multiple L4970A synchronized connecting inputs together external syncr. pulse. 5.1V Vref Device Reference Voltage. Internal Start-up Circuit Drive Power Stage.
RESET RESET DELAY BOOTSTRAP OUTPUT GROUND SUPPLY VOLTAGE FREQUENCY COMPENSATION FEEDBACK INPUT
SOFT START SYNC INPUT Vref Vstart
CIRCUIT OPERATION (refer block diagram) L4970A monolithic stepdown switching regulator working continuous mode realized Technology. This technology allows integration isolated vertical DMOS power transistors plus mixed CMOS/Bipolar transistors. device deliver output voltage adjustable from 5.1V 40V, contains diagnostic control functions that make particularly suitable microprocessor based systems. BLOCK DIAGRAM block diagram shows DMOS power transistor control loop. Integrated functions include reference voltage trimmed 5.1V soft start, undervoltage lockout, oscillator with feedforward control, pulse pulse current limit, thermal shutdown finally reset power fail circuit. reset power fail circuit provides output signal microprocessor indicating status system.
Device turn around with typical hysteresis, this threshold provides correct voltage driving stage DMOS gate hysteresis prevents instabilities. external bootstrap capacitor charged internal voltage reference needed provide correct gate drive power DMOS. driving circuit able source sink peak currents around 0.5A gate DMOS transistor. typical switching time current DMOS transistor 50ns. fast commutation switching frequencies 500kHz possible. control loop consists sawtooth oscillator, error amplifier, comparator, latch output stage. error signal produced comparing output voltage with precise 5.1V chip reference. This error signal then compared with sawtooth oscillator, order generate fixed frequency pulse width modulated drive output stage. latch included eliminate multiple pulsing within period even noisy environments. gain
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L4970A
Figure Feedforward Waveform
Figure Soft Start Function
Figure Limiting Current Function
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L4970A
stability loop adjusted external network connected output error amplifier. voltage feedforward control been added oscillator, this maintains superior line regulation over wide input voltage range. Closing loop directly gives output voltage 5.1V, higher voltages obtained inserting voltage divider. turn output overcurrents prevented soft start function (fig. error amplifier initially clamped external capacitor allowed rise linearly under charge internal constant current source. Output overload protection provided current limit circuit (fig. load current sensed internal metal resistor connected comparator. When load current exceeds preset threshold output comparator sets flip flop which turns power DMOS. next clock pulse, from internal 40kHz oscillator will reset flip flop power DMOS will again conduct. This current protection method, ensures Figure Reset Power Fail Functions. constant current output when system overloaded short circuited limits switching frequency, this condition, 40kHz. Reset Power fail circuitry (fig generates output signal when supply voltage exceeds threshold programmed external voltage divider. reset signal, generated with delay time programmed external capacitor delay pin. When supply voltage falls below threshold output voltage goes below reset output goes immediately. reset output open collector-drain. shows case when supply voltage higher than threshold, output voltage shows case when output 5.1V supply voltage higher than fixed threshold. thermal protection disables circuit operation when junction temperature reaches about 150°C hysterysis prevent unstable conditions.
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L4970A
ELECTRICAL CHARACTERISTICS (Refer test circuit, 25°C, 35V, 16K, 2.2nF, 200KHz typ, unless otherwise specified) DYNAMIC CHARACTERISTICS
Symbol Parameter input Voltage Range (pin Output Votage Line Regulation Load Regulation Test Condition Vref Vref Vref Vref Vref Vref Supply Voltage Ripple Reject. Switching Frequency Voltage Stability Swiching Frequency Temperature Stability Swiching Frequency Maximum Operating Switching Frequency 125°C Vref; 10A; 2VRMS; 100Hz; Vref Min. Typ. Max. Unit Fig. 0.55
Dropout Voltage Between Max. Limiting Current Efficiency
fmax
Vref SECTION (pin
Symbol short Parameter Reference Voltage Line Regulation Load Regulation Average Temperature Coefficient Reference Voltage Short Circuit Current Limit 125°C Test Condition Min. Typ. Max. Unit mV/°C Fig.
VSTART SECTION (pin
Symbol short Parameter Reference Voltage Line Regulation Load Regulation Short Circuit Current Limit Test Condition Min. 11.4 Typ. Max. 12.6 Unit Fig.
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L4970A
ELECTRICAL CHARACTERISTICS (continued) CHARACTERISTICS
Symbol V9on Hyst I9OQ Parameter Turn-on Threshold Turn-off Hysteresys Quiescent Current Operating Supply Current Leak Current 55V; Test Condition Min. Typ. Max. Unit Fig.
SOFT START
Symbol Parameter Soft Start Source Current Output Saturation Voltage Test Condition 20mA; 200µA; Min. Typ. Max. Unit Fig.
ERROR AMPLIFIER
Symbol V10H V10L I10H I10L Parameter High Level Voltage Level Voltage Source Output Current Sink Output Current Input Bias Current Open Loop Gain Supply Voltage Rejection Input Offset Voltage Test Condition -100µA; 4.7V +100µA; 5.3V; 4.7V 5.3V VVCM 50V; Min. Typ. Max. Unit Fig.
RAMP GENERATOR (pin
Symbol Parameter Ramp Valley Ramp Peak Min. Ramp Current Max. Ramp Current Test Condition Min. Typ. Max. Unit Fig.
100µA
SYNC FUNCTION (pin
Symbol I13L I13H Parameter Input Voltage High Input voltage Sync Input Current with Input Voltage Input Current with High Input Voltage Output Amplitude Output Pulse Width Vthr 2.5V Test Condition 50V; 0.9V; 3.5V; Min. -0.3 Typ. Max. Unit Fig.
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L4970A
ELECTRICAL CHARACTERISTICS (continued) RESET POWER FAIL FUNCTIONS
Symbol V11R V11F -I5SO I5SI Parameter Rising Threshold Voltage (pin Falling Threshold Voltage (pin Delay High Threshold Voltage Delay Threshold Voltage Delay Source Current Delay Sink Current Saturation Voltage Output Leak Current Rising Threshold Voltage Hysteresys Input Bias Current Test Condition 5.3V 5.3V 5.3V 5.3V 5.3V; 4.7V; 15mA; 4.7V 50V; 5.3V 4.95 Min. Vref -120 4.77 4.95 5.25 Typ. Vref -100 Vref -200 Max. Vref Vref -160 5.25 Unit Fig.
Figure Test Evaluation Board Circuit
TYPICAL PERFORMANCES (using evaluation board) VREF 200KHz) RIPPLE 30mV 10A) with output filter capacitor Line regulation 50V) Load regulation 15mV 10A) component values, refer test circuit part list.
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L4970A
Figure P.C. Board (components side) Components Layout Figure (1:1 scale).
PARTS LIST
0,5W tab. OPTION 40µH 2.2nF KP1830 220nF 2.2nF MP1830 **C12, C13, 220µF 40VL Film 3300µF 63VL (ROE 2.2µF 390pF Film 22nF 1817 (ERO)
Table
4.7k 4.7k 4.7k 4.7k 6.2kW 9.1k
Table SUGGESTED BOOTSTRAP CAPACITORS
Operating Frequency 20KHz 50KHz 100KHz 200KHz 500KHz Bootstrap Cap.c10 680nF 470nF 330nF 220nF 100nF
1560CT 16A/60V equivalent) core 58071 MAGNETICS TURNS 1,3mm (AWG COGEMA 949178
capacitors parallel increase input current capability capacitors parallel reduce total output
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L4970A
Figure P.C. Board (Back side) Components Layout Circuit Fig. (1:1 scale)
Figure Test Circuits
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L4970A
Figure
Figure
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L4970A
Figure
Figure
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L4970A
Figure Quiescent Drain Current Supply Voltage duty cycle fig. 7A). Figure Quiescent Drain Current Junction Temperature duty cycle).
Figure Quiescent Drain Current Duty Cycle
Figure Reference Voltage (pin14) (see fig.
Figure Reference Voltage (pin Junction Temperature (see fig.
Figure Reference Voltage (pin15) (see fig.
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L4970A
Figure Reference Voltage (pin Junction Temperature (see fig. Figure Reference Voltage 5.1V (pin Supply Voltage Ripple Rejection Frequency
Figure Switching Frequency Input Voltage (see fig.
Figure Switching Frequency Junction Temperature (see
Figure Switching Frequency (see fig.
Figure Max. Duty Cycle Frequency
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L4970A
Figure Supply Voltage Ripple Rejection Frequency (see fig. Figure Line Transient Response (see fig.
Figure Load Transient Response (see fig.
Figure Dropout Voltage Between Current
Figure Dropout Voltage Between Junction Temperature
Figure Power Dissipation (device only) Input Voltage
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L4970A
Figure Power Dissipation (device only) Output Voltage Figure Heatsink Used Derive Device's Power Dissipation Tcase Tamb Heatsink
Figure Efficiency Output Current Figure Efficiency Output Voltage
Figure Efficiency Output Voltage
Figure Open Loop Frequency Phase Response Error Amplifier (see fig.7C)
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L4970A
Figure Power Dissipation Derating Curve
Figure A5.1V/12V Multiple Supply. Note Synchronization between L4970A L4974A
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L4970A
Figure 5.1V Cost Application
Figure Switching Regulator, Adjustable from 25V.
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L4970A
Figure L4970A's Sync. Example
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L4970A
DIM. MIN. Dia1 21.9 21.7 17.65 17.25 10.3 2.65 4.25 4.63 3.65 0.49 0.66 1.02 17.53 19.6
TYP. MAX. 2.65 0.55 0.75 1.27 17.78 1.52 18.03 20.2 22.2 22.1 17.5 10.7 4.55 5.08 22.5 22.5 18.1 17.75 10.9 4.85 5.53 3.85 0.862 0.854 0.695 0.679 0.406 0.104 0.167 0.182 0.075 0.075 0.144 0.019 0.026 0.040 0.690 0.772 MIN.
inch TYP. MAX. 0.197 0.104 0.063 0.039 0.022 0.030 0.050 0.700 0.060 0.710 0.795 0.874 0.870 0.689 0.421 0.179 0.200 0.886 0.886 0.713 0.699 0.429 0.114 0.191 0.218 0.102 0.102 0.152
OUTLINE MECHANICAL DATA
Multiwatt15
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L4970A
Information furnished believed accurate reliable. However, STMicroelectronics assumes responsibility consequences such information infringement patents other rights third parties which result from use. license granted implication otherwise under patent patent rights STMicroelectronics. Specification mentioned this publication subject change without notice. This publication supersedes replaces information previously supplied. STMicroelectronics products authorized critical components life support devices systems without express written approval STMicroelectronics. logo registered trademark STMicroelectronics 2000 STMicroelectronics Printed Italy Rights Reserved STMicroelectronics GROUP COMPANIES Australia Brazil China Finland France Germany Hong Kong India Italy Japan Malaysia Malta Morocco Singapore Spain Sweden Switzerland United Kingdom U.S.A. http://www.st.com
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SWITCHING REGULATOR OUTPUT CURRENT 5.1V OUTPUT VOLTAGE RANGE DUTY

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