Datasheet

ManualsBrandsST ManualsDC / DC Adjustable Switching RegulatorsSwitching Regulator, PDIP, 3.5A

L4974A

June 2000

3.5A SWITCHING REGULATOR

3.5A OUTPUT CURRENT

5.1V TO 40V OUTPUT VOLTAGE RANGE

0 TO 90% DUTY CYCLE RANGE

INTERNAL FEED-FORWARD LINE REG.

INTERNAL CURRENT LIMITING

PRECISE 5.1V ± 2% ON CHIP REFERENCE

RESET AND POWER FAIL FUNCTIONS

INPUT/OUTPUT SYNC PIN

UNDER VOLTAGE LOCK OUT WITH HYS-

TERETIC TURN-ON

PWM LATCH FOR SINGLE PULSE PER PE-

RIOD

VERY HIGH EFFICIENCY

SWITCHING FREQUENCY UP TO 200KHz

THERMAL SHUTDOWN

CONTINUOUS MODE OPERATION

DESCRIPTION

The L4974A is a stepdown monolithic power switch-

ing regulator delivering 3.5A at a voltage variable

from 5.1 to 40V.

Realized with BCD mixed technology, the device

uses a DMOS output transistor to obtain very high

efficiency and very fast switching times. Features of

BLOCK DIAGRAM

POWERDIP

(16 + 2 + 2)

the L4974A include reset and power fail for micro-

processors, feed forward line regulation, soft start,

limiting current and thermal protection. The device

is mounted in a Powerdip 16 + 2 + 2 plastic package

and requires few external components. Efficient

operation at switching frequencies up to 200KHz

allows reduction in the size and cost of external filter

component.

ORDERING NUMBER :

L4974A

1/22

This is advanced information on a new product now in development or undergoing evaluation. Details are subject to change without notice.

MULTIPOWER BCD TECHNOLOGY

Summary of content (23 pages)

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® L4974A 3.5A SWITCHING REGULATOR .. .. .. .. . . .. .. 3.5A OUTPUT CURRENT 5.1V TO 40V OUTPUT VOLTAGE RANGE 0 TO 90% DUTY CYCLE RANGE INTERNAL FEED-FORWARD LINE REG. INTERNAL CURRENT LIMITING PRECISE 5.
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L4974A ABSOLUTE MAXIMUM RATINGS Symbol Parameter Value Unit V11 V11 Input Voltage 55 V Input Operating Voltage 50 V V20 Output DC Voltage Output Peak Voltage at t = 0.
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L4974A PIN FUNCTIONS No Name Function 1 BOOTSTRAP A Cboot capacitor connected between this terminal and the output allows to drive properly the internal D-MOS transistor. 2 RESET DELAY 3 RESET OUT A Cd capacitor connected between this terminal and ground determines the reset signal delay time. Open Collector Reset/power Fail Signal Output. This output is high when the supply and the output voltages are safe. 4 RESET INPUT Input of Power Fail Circuit. The threshold is 5.1V.
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L4974A CIRCUIT OPERATION The L4974A is a 3.5A monolithic stepdown switching regulator working in continuous mode realized in the new BCD Technology. This technology allows the integration of isolated vertical DMOS power transistors plus mixed CMOS/Bipolar transistors. The device can deliver 3.5A at an output voltage adjustable from 5.1V to 40V and contains diagnostic and control functions that make it particularly suitable for microprocessor based systems.
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L4974A Figure 1 : Feedforward Waveform. Figure 2 : Soft Start Function. Figure 3 : Limiting Current Function.
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L4974A Figure 4 : Reset and Power Fail Functions.
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L4974A ELECTRICAL CHARACTERISTICS (refer to the test circuit, TJ = 25°C, Vi = 35V, R4 = 30KΩ, C9 = 2.7nF, fSW = 100KHz typ, unless otherwise specified) DYNAMIC CHARACTERISTICS Symbol Parameter Vi Input Volt. Range (pin 11) Vo = Vref to 40V Io = 3.5A (*) Test Conditions 15 Max. Unit Fig. 50 V 5 Vo Output Voltage Vi =15V to 50V Io = 2A; Vo = Vref 5 5.1 5.2 V 5 ∆Vo Line Regulation VI = 15V to 50V Io = 1A; Vo = Vref 12 30 mV ∆Vo Load Regulation VO = Vref Io = 1A to 3.
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L4974A ELECTRICAL CHARACTERISTICS (continued) DC CHARACTERISTICS Symbol Parameter V11on V11 Hyst Turn-on Threshold I11Q Quiescent Current I11OQ I20L Test Condition Min. Typ. Max. Unit 10 11 12 V 7A V 7A mA 7A Turn-off Hysteresys 1 Fig.
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L4974A ELECTRICAL CHARACTERISTICS (continued) RESET AND POWER FAIL FUNCTIONS Symbol Min. Typ. Max. Unit Fig. Rising Thereshold Voltage (pin 9) Falling Thereshold Voltage (pin 9) Vi = 15 to 50V V4 = 5.3V Vi = 15 to 50V V4 = 5.3V Vref -130 4.77 Vref -100 Vref -200 Vref -80 Vref -160 V mV V mV 7D V2H Delay High Threshold Volt. Vi = 15 to 50V V4 = 5.3V V9 = V13 4.95 5.1 5.25 V 7D V2L Delay Low Threshold Volt. Vi = 15 to 50V V4 = 4.7V V9 = V13 1 1.1 1.
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L4974A Figure 6a : Component Layout of fig.5 (1 : 1 scale). Evaluation Board Available PART LIST R1 = 30KΩ R2 = 10KΩ R3 = 15KΩ R4 = 30KΩ R5 = 22Ω R6 = 4.7KΩ R7 = see table A R8 = OPTION R9 = 4.7KΩ * C1 = C2 = 1000µF 63V EYF (ROE) C3 = C4 = C5 = C6 = 2,2µF 50V C7 = 390pF Film C8 = 22nF MKT 1837 (ERO) C9 = 2.7nF KP 1830 (ERO) C10 = 0.33µF Film C11 = 1nF ** C12 = C13 = C14 = 100µF 40V EKR (ROE) C15 = 1µF Film D1 = SB 560 (OR EQUIVALENT) L1 = 150µH core 58310 MAGNETICS 45 TURNS 0.
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L4974A Figure 6b: P.C. Board and Component Layout of the Circuit of Fig. 5. (1:1 scale) Figure 7 : DC Test Circuits.
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L4974A Figure 7A. Figure 7B. Figure 7C.
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L4974A Figure 7D. Figure 8 : Quiescent Drain Current vs. Supply Voltage (0% duty cycle - see fig. 7A). Figure 9 : Quiescent Drain Current vs. Junction Temperature (0% duty cycle).
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L4974A Figure 10 : Quiescent Drain Current vs. Duty Cycle. Figure 11 : Reference Voltage (pin 13) vs. Vi (see fig. 7). Figure 12 : Reference Voltage (pin 13) vs. Junction Temperature (see fig. 7). Figure 13 : Reference Voltage (pin 14) vs. Vi (see fig. 7). Figure 14 : Reference Voltage (pin 14) vs. Junction Temperature (see fig. 7). Figure 15 : Reference Voltage 5.1V (pin 13) Supply Voltage Ripple Rejection vs.
PAGE 15
L4974A Figure 16 : Switching Frequency vs. Input Voltage (see fig. 5). Figure 17 : Switching Frequency vs. Junction Temperature (see fig. 5). Figure 18 : Switching Frequency vs. R4 (see fig.5). Figure 19 : Maximum Duty Cycle vs. Frequency. Figure 20 : Supply Voltage Ripple Rejection vs. Frequency (see fig. 5). Figure 21 : Efficiency vs. Output Voltage.
PAGE 16
L4974A Figure 22 : Line Transient Response (see fig. 5). Figure 23 : Load Transient Response (see fig. 5). Figure 24 : Dropout Voltage between Pin 11 and Pin 20 vs. Current at Pin 20. Figure 25 : .Dropout Voltage between Pin 11 and Pin 20 vs. Junction Temperature. Figure 26 : Power Dissipation (device only) vs. Input Voltage. Figure 27 : Power Dissipation (device only) vs. Input Voltage.
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L4974A Figure 28 : Power Dissipation (device only) vs. Output Voltage. Figure 29 : Power Dissipation (device only) vs. Output Voltage. Figure 30 : Power Dissipation (device only) vs. Output Current. Figure 31 : Power Dissipation (device only) vs. Output Current. Figure 32 : Efficiency vs. Output Current. Figure 33 : Test PCB Thermal Characteristic.
PAGE 18
L4974A Figure 34 : Junction to Ambient Thermal Resistance vs. Area on Board Heatsink (DIP 16+2+2) Figure 36: Open Loop Frequency and Phase of Error Amplifier (see fig. 7C). 18/22 Figure 35: Maximum Allowable Power Dissipation vs.
PAGE 19
L4974A Figure 37 : 3.5A – 5.1V Low Cost Application Circuit. Figure 38 : A 5.1V/12V Multiple Supply. Note the Synchronization between the L4974A and L4970A.
PAGE 20
L4974A Figure 39 : L4974A’s Sync. Example. Figure 40: 1A/24V Multiple Supply.
PAGE 21
L4974A mm DIM. MIN. a1 0.51 B 0.85 b b1 TYP. inch MAX. MIN. TYP. MAX. 0.020 1.40 0.033 0.50 0.38 0.055 0.020 0.50 D 0.015 0.020 24.80 0.976 E 8.80 0.346 e 2.54 0.100 e3 22.86 0.900 F 7.10 0.280 I 5.10 0.201 L OUTLINE AND MECHANICAL DATA 3.30 0.130 Powerdip 20 Z 1.27 0.
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L4974A Information furnished is believed to be accurate and reliable. However, STMicroelectronics assumes no responsibility for the consequences of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of STMicroelectronics. Specification mentioned in this publication are subject to change without notice.
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