L4962
1.5A POWER SWITCHING REGULATOR
1.5A OUTPUT CURRENT
5.1V TO40V OUTPUT VOLTAGE RANGE
PRECISE(±2%)ON-CHIP REFERENCE
HIGH SWITCHING FREQUENCY
VERY HIGH EFFICIENCY(UP TO90%)
VERY FEW EXTERNAL COMPONENTS
SOFT START
INTERNAL LIMITING CURRENT
THERMAL SHUTDOWN
DESCRIPTION
The L4962is a monolithic power switching regula-tor delivering1.5A at a voltage variable from5V to 40V in step down configuration.
Features of the device include current limiting,soft start,thermal protection and0to100%duty cycle for continuous operating mode.
March1996
ORDERING NUMBERS:L4962/A(12+2+2Powerdip)
金银岛简介
L4962E/A(Heptawatt)
L4962EH/A(Horizontal
Heptawatt)
The L4962is mountedin a16-lead Powerdip plastic package and Heptawatt packageand requires very few external components.
Efficient operation at switching frequencies up to 150KHz allows a reduction in the size and cost of external filter components.
HEPTAWATT
POWERDIP
(12+2+2)
BLOCK DIAGRAM
Pin X=Powerdip
Pin(X)=Heptawatt
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PIN CONNECTION (T op view)
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Symbol Parameter
Heptawatt Powerdip R th j-ca Thermal resistance junction-ca max 4°C/W -R th j-pins Thermal resistance junction-pins max -14°C/W R th j-amb
Thermal resistance junction-ambient
max
50°C/W
80°C/W*
*Obtained with the GND pins soldered to printed circuit with minimized copper area.
THERMAL DATA
HEPTAWATT POWERDIP
NAME
FUNCTION
1
7
SUPPLY VOLTAGE
Unregulated voltage input.An internal regulator powers the internal logic.
210FEEDBACK INPUT
The feedback terminal of the regulation loop.The output is connected directly to this terminal for 5.1V operation;it is connected via a divider for higher voltages.311
FREQUENCY COMPENSATION
A ries RC network connected between this terminal and ground determines the regulation loop gain characteristics.
PIN FUNCTIONS
Symbol Parameter
Value Unit V 7Input voltage
50V V 7-V 2Input to output voltage difference 50V V 2Negative output DC voltage
-1V Output peak voltage at t =0.1µs;f =100KHz -5V V 11,V 15Voltage at pin 11,15 5.5V V 10Voltage at pin 107V I 11Pin 11sink current 1mA I 14Pin 14source current
20mA P tot Power dissipation at T pins ≤90°C (Powerdip)
T ca ≤90°C (Heptawatt) 4.315W W T j ,T stg
Junction and storage temperature
-40to 150
°C
ABSOLUTE MAXIMUM RATINGS
L4962
Symbol
Parameter
Test Condition s
Min.
Typ.
Max.
Unit
DYNAMIC CHARACTERISTICS
V o Output voltage range V i =46V I o =1A V ref 40V V i Input voltage range V o =V ref to 36V I o =1.5A 9
46V ∆V o Line regulation V i =10V to 40V V o =V ref
I o =1A
1550mV ∆V o Load regulation
V o =V ref I o =0.5A to 1.5A 8
20mV V ref Internal reference voltage (pin 10)
V i =9V to 46V I o =1A
5
5.1
5.2
V
∆V ref ∆T Average temperature
coefficient of refer.voltage T j =0°C to 125°C I o =1A 0.4mV/°C
V d Dropout voltage I o =1.5A 1.52V I om Maximum operating load current
偏口
V i =9V to 46V V o =V ref to 36V 1.5A I 2L Current limiting threshold (pin 2)
V i =9V to 46V V o =V ref to 36V 2
垦丁大街
3.3A I SH Input average current V i =46V;output short-circuit
1530
mA η
Efficiency
f =100KHz V o =V ref 70%I o =1A
V o =12V
80%SVR
Supply voltage ripple rejection
∆V i =2V rms fripple =100Hz V o =V ref
Io =1A
50
56
dB
ELECTRICAL CHARACTERISTICS (Refer to the test circuit,T j =25°C,V i =35V,unless otherwi specified)
HEPTAWATT POWERDIP NAME FUNCTION
44,5,12,13
GROUND Common ground terminal.
5
14
OSCILLATOR
A parallel RC network connected to this terminal determines the switching frequency.This pin must be connected to pin 7input when the internal oscillator is ud.
615SOFT START
Soft start time constant.A capacitor is connected between this terminal and ground to define the soft start time constant.This capacitor also determines the average short circuit output current.72OUTPUT
Regulator output.1,3,6,8,9,16
N.C.
PIN FUNCTIONS (cont’d)
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L4962
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Symbol
Parameter
Test Conditions
Min.
Typ.
Max.
Unit
DYNAMIC CHARACTERISTICS (cont’d)
f Switchin
g frequency 85
100115
KHz ∆f ∆V i Voltage stability of switching frequency V i =9V to 46V
0.5
%
∆f ∆T j Temperature stability of switching frequency T j =0°C to 125°C 1%
f max Maximum operatin
g switching frequency V o =V ref
I o =1A
120
150KHz T sd
Thermal shutdown junction temperature
150
°C
90后女生
DC CHARACTERISTICS
I 7Q
Quiescent drain current
100%duty cycle pins 2and 14open
V i =46V
30
40
mA
0%duty cycle
15
20mA -I 2L
Output leakage current
0%duty cycle
1
mA
青春是一本太仓促的书SOFT START
I 15SO Source current 100140180µA I 15SI
Sink current田园乐其六
50
70
120
µA
ERROR AMPLIFIER
V 11H High level output voltage V 10=4.7V I 11=100µA 3.5
V V 11L Low level output voltage V 10=5.3V I 11=100µA
0.5
V I 11SI Sink output current V 10=5.3V 100150µA -I 11SO Source output current V 10=4.7V 100
150µA I 10Input bias current V 10=5.2V 210
µA G v
DC open loop gain残缺的美丽
V 11=1V to 3V
46
55
dB
OSCILLATOR
-I 14
Oscillator source current
5
mA
ELECTRICAL CHARACTERISTICS (continued)
L4962
CIRCUIT OPERATION(refer to the block diagram)
The L4962isa monolithic stepdownswitching regu-lator providing outputvoltagesfrom5.1V to40V and delivering1.5A.
The regulation loop consists of a sawtooth oscilla-tor,error amplifier,comparator and the output stage.An error signal is producedby comparing the output voltage with a preci5.1V on-chip refer-e
nce(zener zap trimmed to±2%).
This errorsignal is then comparedwith the sawtooth signal to generate the fixed frequency pul width modulated puls which drive the output stage. The gain and frequency stability of the loop can be adjusted by an external RC network connected to pin11.Closing the loop directly gives an output voltage of5.1V.Higher voltages are obtained by inrting a voltage divider.
Output overcurrents at switch on are prevented by the soft start function.The error amplifier output is initially clamped by the external capacitor C ss and allowed to ri,linearly,as this capacitor is charged by a constant current source.Output overload pro-tection is provided in the form of a current limiter. The load current is nd by an internal metal resistor connected to a comparator.When the load current exceeds a pret threshold this comparator ts a flip flop which disables the output stage and discharges the soft start capacitor.A cond com-parator rets the flip flop when the voltage across the soft start capacitor has fallen to0.4V.
The output stage is thus re-enabled and the output voltage ris under control of the soft start network. If the overload condition is still prent the limiter will trigger again when the threshold current is reached.The average short circuit current is limited to a safe value by the dead time introd
uced by the soft start network.The thermal overload circuit dis-ables circuit operation when the junction tempera-ture reaches about150°C and has hysteresis to prevent unstable conditions.
Figure1.Soft start waveforms
Figure2.Current limiter waveforms
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L4962
Figure 4.Quiescent drain current vs.supply voltage(0% duty cycle)Figure 5.Quiescent drain
current vs.supply voltage
(100%duty cycle)
Figure 6.Quiescent drain
current vs.junction tem-同仁堂金匮肾气丸
perature(0%duty cycle)
Figure3.Test and application circuit(Powerdip)
1)D1:BYW98or3A Schottky diode,45V of VRRM;
2)L1:CORE TYPE-MAGNETICS58120-A2MPP
N°TURNS45,WIRE GAUGE:0.8mm(20AWG)
3)C6,C7:ROE,EKR220µF40V
L4962
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