SWITCHING REGULATOR OUTPUT CURRENT 5.1V OUTPUT VOLTAGE RANGE DUTY
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L4972A L4972AD
SWITCHING REGULATOR
OUTPUT CURRENT 5.1V OUTPUT VOLTAGE RANGE DUTY CYCLE RANGE INTERNAL FEED-FORWARD LINE REG. INTERNAL CURRENT LIMITING PRECISE 5.1V CHIP REFERENCE RESET POWER FAIL FUNCTIONS INPUT/OUTPUT SYNC UNDER VOLTAGE LOCK WITH HYSTERETIC TURN-ON LATCH SINGLE PULSE PERIOD VERY HIGH EFFICIENCY SWITCHING FREQUENCY 200KHz THERMAL SHUTDOWN CONTINUOUS MODE OPERATION
MULTIPOWER TECHNOLOGY
ERDIP
SO20
ORDERING NUMBERS L4972A (Powerdip) L4972AD (SO20)
DESCRIPTION L4972Aisa stepdownmonolithicpower switching regulatordelivering voltagevariable from 40V. Realized with mixed technology, device uses DMOS output transistor obtain very high efficiency very fast switching times. Features BLOCK DIAGRAM
L4972A include reset power fail microprocessors, feed forward line regulation, soft start, limiting current thermal protection. device mountedin Powerdip16 SO20large plastic packages requires external components. Efficient operation switching frequencies 200KHz allows reduction size cost external filter component.
June 2000
1/23
This advanced information product development undergoing evaluation. Details subject change without notice.
L4972A-L4972AD
ABSOLUTE MAXIMUM RATINGS
Symbo Ptot Tstg
SO-20
Parameter Input Voltage Input Operating Voltage Output Voltage Output Peak Voltage 0.1µs 200khz Maximum Output Current Boostrap Voltage Boostrap 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 TPINS 90°C 70°C copper area PCB) Junction Storage Temperature
Valu Internally Limited 3.75(*) 1.3/1
Unit
CONNECTION (top view)
THERMAL DATA
Symb j-pins j-amb Parameter Thermal Resistance Junction-Pins Thermal Resistance Junction-ambient werdip 12°C/W 60°C/W 16°C/W 80°C/W
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L4972A-L4972AD
FUNCTIONS
Name BOOTSTRAP RESET DELAY RESET RESET INPUT unctio Cboot capacitor connected between this terminal output allows drive properly internal D-MOS transistor. capacitor connected between this terminal ground determines reset signal delay time. Open Collector Reset/power Fail Signal Output. This output high when supply output voltages safe. Input Power Fail Circuit. threshold 5.1V. connected divider input power fail function. mustbe connected external resistor when power fail signal required. Common Ground Terminal series network connected between this terminal ground determines regulation loop gain characteristics. Soft Start Time Constant. capacitor connected between sterminal ground define soft start time constant. Feedback Terminal Regulation Loop. output connected directly this terminal 5.1V operation; connected divider higher voltages. Multiple L4972A's synchronized connecting inputs together external syncr. pulse. Unregulated Input Voltage. Connected. 5.1V Vref Device Reference Voltage. Internal Start-up Circuit Drive Power Stage. Rosc. External resistor connected ground determines constant charging current osc. Cosc. External capacitor connected ground determines (with Rosc) switching frequency. Regulator Output.
GROUND FREQUENCY COMPENSATION SOFT START FEEDBACK INPUT SYNC INPUT SUPPLY VOLTAGE N.C. Vref Vstart OSCILLATOR OSCILLATOR OUTPUT
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L4972A-L4972AD
CIRCUIT OPERATION L4972A monolithic stepdown switching regulatorworking continuousmode realized inthe Technology. This technology allows integration isolatedvertical DMOS power transistors plus mixed CMOS/Bipolar transistors. device deliver output voltage adjustable from 5.1V contains diagnostic control functions that make particularly suitable microprocessor based systems. BLOCK DIAGRAM block diagram shows DMOS power transistors control loop. Integrated functions include reference voltage trimmed 5.1V 2%,soft start, undervoltagelockout, 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 hysterysis, this threshold porvides correct voltage driving stage DMOS gate hysterysis prevents instabilities. 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 200kHz possible. control loop consists sawtooth oscillator, error amplifier, comparator, latch output stage. error signal producedby comparing onchip reference. This error signal then compared with sawtooth oscillator order generate frixed frequency pulse width modulated drive output stage. latch included eliminate multiple pulsing within period even noisy environments. gain stabilityof loop adjustedby
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 outputvoltage 5.1V, higher voltages areobtained inserting voltage divider. turn outputovercurrents preventedby soft start function (fig. error amplifier initially clamped externalcapacitor,Css, allowed rise linearly under charge internal constant current source. Output overload protection provided current limit circuit. load current sensedby internal metalresistor connectedto 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 flopand power DMOS will again conduct. This current protection method,ensuresa constantcurrent outputwhenthe systemis overloadedor shortcircuited limitsthe switching frequency, this condition,to 40kHz. Reset Power fail circuit (fig. generates output signal when supply voltage exceeds threshold programmed external voltage divider. reset signal, generated with delay time programmedby externalcapacitor delay pin. When supply voltage falls below threshold output voltage goes below resetoutput goes immediately. reset output open drain. Fig. shows case when supply voltage higher than threshold, output voltage Fig. 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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L4972A-L4972AD
Figure Feedforward Waveform.
Figure Soft Start Function.
Figure Limiting Current Function.
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L4972A-L4972AD
Figure Reset Power Fail Functions.
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L4972A-L4972AD
ELECTRICAL CHARACTERISTICS (refer test circuit, 25°C, 35V, 30K, 2.7nF, 100KHztyp, unless otherwise specified) DYNAMIC CHARACTERISTICS
Symbo I20L Parameter Input Volt. Range (pin Output Voltage Line Regulation Load Regulation Dropout Voltage between Limiting Current Efficiency itions Vref (**) =15V Vref 0.5A; Vref Vref 0.5A Vref 100KHz Vref 2VRMS; 100Hz; Vref Min. 0.25 Max. Unit
f/Vi
Supply Voltage Ripple Rejection Switching Frequency Voltage Stability Switching Frequency Temperature Stability Switching Frequency Maximum Operating Switching Frequency
f/Tj fmax
125°C Vref 2.2nF
Only version
(**) Pulse testing with duty cycle
Vref SECTION (pin
Symbo short Parameter Reference Voltage Line Regulation Load Regulation Average Temperature Coefficient Reference Voltage Short Circuit Current Limit 125°C Cond ition Min. Max. Unit mV/°C
VSTART SECTION (pin
Symbo short Parameter Reference Voltage Line Regulation Load Regulation Short Circuit Current Limit Cond ition Min. 11.4 Max. 12.6 Unit
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L4972A-L4972AD
ELECTRICAL CHARACTERISTICS (continued) CHARACTERISTICS
Symbo V11on Hyst I11Q I11OQ I20L Parameter Turn-on Threshold Turn-off Hysteresys Quiescent Current Operating Supply Current Leak Current 55V; Cond ition Min. Typ. Max. Unit
SOFT START (pin
Symbo Parameter Soft Start Source Current Output Saturation Voltage Cond ition 20mA; 200µA; Min. Typ. Max. Unit
ERROR AMPLIFIER
Symbo -I7L Parameter High Level Voltage Level Voltage Source Output Current Sink Output Current Input Bias Current Open Loop Gain Supply Voltage Rejection Input Offset Voltage Cond ition 100µA; 4.7V 100µA; 5.3V; 4.7V 5.3V Min. Typ. Max. Unit
RAMP GENERATOR (pin
Symbo Parameter Ramp Valley Ramp Peak Min. Ramp Current Max. Ramp Current Cond ition Min. Typ. Max. Unit
100µA
SYNC FUNCTION (pin
Symbo I10L I10H Parameter Input Voltage High Input voltage Cond ition 50V; Min. -0.3 Typ. Max. Vthr 2.5V Unit
Sync Input Current with 0.9V; Input Voltage Input Current with High 2.5V Input Voltage Output Amplitude Output Pulse Width
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ELECTRICAL CHARACTERISTICS (continued) RESET POWER FAIL FUNCTIONS
Symbo I2SO I2SI Parameter Rising Thereshold Voltage (pin Falling Thereshold Voltage (pin Delay High Threshold Volt. Delay Threshold Volt. Delay Source Current Delay Source Sink Current Output Saturation Voltage Output Leak Current Rising Threshold Voltage Hysteresis Input Bias Current itions 5.3V 5.3V 5.3V 4.7V 5.3V; 4.7V; 15mA; 4.7V 50V; 4.95 Min. Vref -130 4.77 4.95 5.25 Vref -100 Vref -200 Max. Vref Vref -160 5.25 Unit
TYPICAL PERFORMANCES (using evaluation board) VREF 100KHz) RIPPLE 30mV Line regulation 12mV 50V) Load regulation component values Refer fig. (Part list).
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L4972A-L4972AD
Figure Component Layout fig.5 scale). Evaluation Board Available (only version)
PART LIST
4.7K table OPTION 4.7K 1000µF (ROE) 2,2µF 390pF Film 22nF 1837 (ERO) 2.7nF 1830 (ERO) 0.33µF Film 100µF (ROE) Film EQUIVALENT) 150µH core 58310 MAGNETICS TURNS 0.91mm (AWG COGEMA 949181
capacitors parallel increase input current capability. capacitors parallel reduce total output ESR.
Table
4.7k 4.7k 4.7k 4.7k 6.2kW 9.1k
Note: Test Application Circuit L4972D mounted
Table SUGGESTED BOOSTRAP CAPACITORS
Operatin requency 20KHz 50KHz 100KHz 200KHz 500KHz strap Cap.c10 680nF 470nF 330nF 220nF 100nF
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L4972A-L4972AD
Figure P.C. Board Component Layout Circuit Fig. (1:1 scale)
Figure Test Circuits.
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L4972A-L4972AD
Figure
Figure
Figure
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Figure
Figure Quiescent Drain Current Supply Voltage duty cycle fig. 7A).
Figure QuiescentDrain Current Junction Temperature duty cycle).
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L4972A-L4972AD
Figure Quiescent Drain Current Duty Cycle. Figure Reference Voltage (pin (see fig.
Figure Reference Voltage (pin Junction Temperature (see fig.
Figure ReferenceVoltage (pin (see fig.
Figure Reference Voltage (pin Junction Temperature (see fig.
Figure Reference Voltage 5.1V (pin Supply Voltage Ripple Rejection FreSVR (dB)
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L4972A-L4972AD
Figure Switching Frequency Input Voltage (see fig. Figure Switching Frequency Junction Temperature (see fig.
Figure Switching Frequency (see fig.5).
Figure Maximum Duty Cycle Frequency.
Figure Supply Voltage Ripple Rejection Frequency (see fig.
Figure Efficiency Output Voltage.
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L4972A-L4972AD
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.
Figure Power Dissipation (device only) Input Voltage.
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L4972A-L4972AD
Figure Power Dissipation (device only) Output Voltage. Figure Power Dissipation (device only) OutputVoltage.
Figure Power Dissipation (device only) Output Current.
Figure Power Dissipation (device only) Output Current.
Figure Efficiency Output Current.
Figure Test Thermal Characteristic.
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L4972A-L4972AD
Figure Junctionto AmbientThermal Resistance Area onBoard Heatsink (DIP 16+2+2) Figure Junction Ambient Thermal Resistance Area Board Heatsink (SO20)
Figure Maximum Allowable Power Dissipation Ambient Temperature (Powerdip)
Figure Maximum Allowable Power Dissipation Ambient Temperature (SO20)
Figure Open Loop Frequency Phase Error Amplifier (see fig. 7C).
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L4972A-L4972AD
Figure 5.1V Cost Application Circuit.
Figure 5.1V/12VMultiple Supply. Note Synchronization between L4972A L4970A.
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L4972A-L4972AD
Figure L4972A's Sync. Example.
Figure 1A/24V Multiple Supply. Note synchronization between L4972A L4962
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L4972A-L4972AD
DIM. MIN. 0.38 0.51 0.85
TYP. MAX. MIN. 0.020 1.40 0.50 0.50 24.80 8.80 2.54 22.86 7.10 5.10 3.30 1.27 0.015 0.033
inch TYP. MAX.
OUTLINE MECHANICAL DATA
0.055 0.020 0.020 0.976 0.346 0.100 0.900 0.280 0.201 0.130 0.050
Powerdip
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L4972A-L4972AD
DIM. MIN. 0.25 2.35 0.33 0.23 12.6
TYP. MAX. 2.65 0.51 0.32 1.27 10.65 0.75 1.27 0.394 0.010 0.016 MIN. 0.093 0.004 0.013 0.009 0.496 0.291
inch TYP. MAX. 0.104 0.012 0.020 0.013 0.512 0.299 0.050 0.419 0.030 0.050
OUTLINE MECHANICAL DATA
SO20
(min.)8° (max.)
SO20MEC
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L4972A-L4972AD
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