Text preview for : L4947.pdf part of SGS-Thomson L4947 L4947 & L4947R 5V-0.5A very low drop regulator with reset

Back to : L4947.pdf | Home

L4947 L4947R
PRECISE OUTPUT VOLTAGE (5V 4%) OVER FULL TEMPERATURE RANGE ( 40 / 125 C) VERY LOW VOLTAGE DROP (0.75Vmax) OVER FULL T RANGE OUTPUT CURRENT UP TO 500mA RESET FUNCTION POWER-ON RESET DELAY PULSE DEFINED BY THE EXTERNAL CAPACITOR + 80V LOAD DUMP PROTECTION 80V LOAD DUMP PROTECTION REVERSE VOLTAGE PROTECTION SHORT CIRCUIT PROTECTION AND THERMAL SHUT-DOWN (with hysteresis) LOW START UP CURRENT DESCRIPTION The L4947/L4947R is a monolithic integrated circuit in Pentawatt package specially designed to provide a stabilized supply voltage for automotive and industrial electronic systems. Thanks to its very low voltage drop, in automotive applications the L4947/L4947R can work correctly even during the cranking phase, when the battery voltage BLOCK DIAGRAM

Pentawatt ORDERING NUMBER: L4947 L4947R

could fall as low as 6V. Furthermore, it incorporates a complete range of protection circuits against the dangerous overvoltages always present on the battery rail of the car. The reset function makes the device particularly suited to supply microprocessor based systems : a signal is available (after an externally programmable delay) to reset the microprocessor at power-on phase ; at power-off, this signal becomes low inhibiting the microprocessor.

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

December 1991


L4947 - L4947R
Symbol Vi Parameter DC Input Voltage DC Reverse Input Voltage Transient Input Overvoltages : Load Dump : 5ms trise 10ms f Fall Time Constant = 100ms RSOURCE 0.5 Field Decay : 5ms tfall 10ms, RSOURCE 10 r Rise Time Constant = 33ms Low Energy Spike : trise = 1s, tfall = 500s, R SOURCE 10 fr Repetition Frequency = 5Hz Reset Output Voltage Junction and Storage Temperature Range Value 35 18 80 Unit V V V

80 100


VR TJ, Tstg

35 55 to 150


Note: The circuit is ESD protected according to MIL-STD-883C.


Symbol Rth j-case Parameter Thermal Resistance Junction-case Max Value 3.5 Unit C/W


(*) Min. 20F, ESR < 10 over full temperature range R P (pull up resistor) and RL (load) are both equal to 1K.


L4947 - L4947R
ELECTRICAL CHARACTERISTICS (refer to the test circuit, Vi = 14. 4V, Co = 47F, ESR < 10, Rp = 1K, RL = 1K, 40C TJ 125C, unless otherwise specified)
Symbol Vo Parameter Output Voltage Test Conditions Io = 0mA to 500mA Over Full T Range TJ = 25C Io = 0mA to (*) 500mA Vi = 6V to 26V ; Io = 5mA Io = 5mA to 500mA Io = 500mA, TJ = 25C Over Full T Range Io = 0mA, TJ = 25C Io = 0mA Over Full T Io = 500mA Over Full T Min. 4.80 4.90 6 Typ. 5.00 5.00 2 15 0.40 5 6.5 110 0.5 50 60 Max. 5.20 5.10 26 10 60 0.55 0.75 10 13 180 Unit V V V mV mV V V mA mA mA mV/C dB

Vi Vo Vo Vi V o Iq

Operating Input Voltage Line Regulation Load Regulation Dropout Voltage Quiescent Current


Temperature Output Voltage Drift Supply Volt. Rej.

Io = 350mA ; f = 120Hz C o = 100F ; Vi = 12V 5V pp 1.5V < Vo < VRT (off), IR = 1.6mA 3.0V < Vo < VRT (off), IR = 8mA VO in Regulation, VR = 5V 1K Reset Pull-up to Vo, TJ = 25C TJ = 25C L4947: Vo @ Reset Out H to L Transition L4947R: Vo @ Reset Out H to L Transition Vo @ Reset Out L to H Transition VRT (on) V RT (off) Vd @ Reset Out L to H Transition Vd @ Reset Out H to L Transition Vd = 3V, TJ = 25C Vo < VRT (off) C d = 100nF, TJ = 25C

Isc VR

Output Short Circuit Current Reset Output Saturation Voltage



1.50 0.40 0.40 50 0.80


IR VRT pe ak VRT (off)

Reset Output Leakage Current Power On-Off Reset out Peak Voltage Power OFF Vo Threshold


4.70 4.75 4.55

Vo 0.15 Vo 0.30 VRT (off) + 0.05 0.05 4.00 3.55 0.45 20 0.55 1.20 30 Vo 0.04 4.35 3.90

V V V V V V V V /A V ms

VRT (on) VHyst Vd

Power ON Vo Threshold Power ON-Off Hysteresis Delay Comparator Threshold

3.65 3.20

VdH Id Vdisch Td

Delay Comparator Hysteresis Delay Capacitor Charging Current Delay Capacitor Discharge Voltage Power on Reset Delay Time



(*) For a DC voltage 26 < Vi < 37V the device is not operating

FUNCTIONAL DESCRIPTION The L4947/L4947R is a very low drop 5V/0.5A voltage regulator provided with a reset function and therefore particularly suited to meet the requirements of supplying the microprocessor systems used in automotive and industrial applications. The block diagram shows the basic structure of the device : the reference, the error amplifier, the

driver, the power PNP, the protection and reset functions. The power stage is a Lateral PNP transistor which allows a very low dropout voltage (typ. 400mV at TJ = 25C, max. 750mV over the full temperature range @ IO = 500mA). The typical curve of the dropout voltage as a function of the junction temperature is shown in Fig. 1 : that is the worst case, where IO = 500mA.

L4947 - L4947R
The current consumption of the device (quiescent current) is maximum 13mA - over full T - when no load current is required. The internal antisaturation circuit allows a drastic reduction in the current peak which takes place during the start up. The reset function supervises the regulator output voltage inhibiting the microprocessor when the device is out of regulation and resetting it at the power-on after a settable delay. The reset is LOW when the output voltage value is lower than the reset threshold voltage. At the power-on phase the output voltage increases (see Fig. 2) and when it reaches the power-on VO threshold VRT (On) - the reset output becomes HIGH after a delay time set by the external capacitor Cd. At the power-off the output voltage decreases : at the VRT(Off) threshold value (VO-0.15V typ. for L4947 and VO-0.3V typ. for L4947R value) the reset outFigure 1: Typical Dropout Voltage vs. Tj (Io = 500mA). put instantaneously goes down (LOW status) inhibiting the microprocessor. The typical power onoff hysteresis is 50mV. The three gain stages (operational amplifier, driver and power PNP) require the external capacitor (Comin = 20F) to guarantee the global stability of the system. Load dump and field decay protections ( 80V), reverse voltage ( 18V) and short circuit protection, thermal shutdown are the main features that make the L4947/L4947R specially suitable for applications in the automotive enviroment. EXTERNAL COMPENSATION Since the purpose of a voltage regulator is to supply and load variations, the open loop gain of the regulator must be very high at low frequencies. This may cause instability as a result of the various poles present in the loop. To avoid this instability dominant pole compensation is used to reduce phase shift due to other poles at the unity gain frequency. The lower the frequency of these others poles at the unity gain frequency. The lower the frequency of these other poles, the greater must be capacitor esed to create the dominant pole for the same DC gain. Where the output transistor is a lateral PNP type there is a pole in the regulation loop at a frequencybtoo low to be compensated by a capacitor which can be integrated. An external compensation is therefore necessary so a very high value capacitor must be connected from the output to ground. The paeassitic equivalent series resistance of the capacitor used adds a zero to the regulation loop. This zero may compromise the stability of the system since its effect tends to cancel the effect of the pole added. In regulators this ESR must be less than 3 and the minimum capacitor value is 47F.

Figure 2: Reset Waveforms: (1) Without External Capacitor Cd. (2) With External Capacitor Cd.


L4947 - L4947R
DIM. A C D D1 E F F1 G G1 H2 H3 L L1 L2 L3 L5 L6 L7 M M1 Dia 3.65 2.6 15.1 6 4.5 4 3.85 0.144 10.05 17.85 15.75 21.4 22.5 3 15.8 6.6 0.102 0.594 0.236 0.177 0.157 0.152 2.4 1.2 0.35 0.8 1 3.4 6.8 10.4 10.4 0.396 0.703 0.620 0.843 0.886 0.118 0.622 0.260 MIN. mm TYP. MAX. 4.8 1.37 2.8 1.35 0.55 1.05 1.4 0.094 0.047 0.014 0.031 0.039 0.126 0.260 0.134 0.268 MIN. inch TYP. MAX. 0.189 0.054 0.110 0.053 0.022 0.041 0.055 0.142 0.276 0.409 0.409

L E L1 M1 A C D1 L2 L5 L3 H3 D Dia. F L6 H2 L7 F1 G G1 M


L4947 - L4947R

Information furnished is believed to be accurate and reliable. However, SGS-THOMSON Microelectronics 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 SGS-THOMSON Microelectronics. Specifications mentioned in this publication are subject to change without notice. This publication supersedes and replaces all information previously supplied. SGS-THOMSON Microelectronics products are not authorized for use as critical components in life support devices or systems without express written approval of SGS-THOMSON Microelectronics. 1994 SGS-THOMSON Microelectronics - All Rights Reserved PENTAWATT is a Registered Trademark of SGS-THOMSON Microelectronics SGS-THOMSON Microelectronics GROUP OF COMPANIES Australia - Brazil - France - Germany - Hong Kong - Italy - Japan - Korea - Malaysia - Malta - Morocco - The Netherlands - Singapore Spain - Sweden - Switzerland - Taiwan - Thaliand - United Kingdom - U.S.A.