®
L4960
2.5A POWER SWITCHING REGULATOR
2.5A OUTPUT CURRENT
5.1V TO 40V OPUTPUT VOLTAGE RANGE PRECISE (± 2%) ON-CHIP REFERENCE HIGH SWITCHING FREQUENCY
VERY HIGH EFFICIENCY (UP TO 90%)VERY FEW EXTERNAL COMPONENTS SOFT START
INTERNAL LIMITING CURRENT THERMAL SHUTDOWN
DESCRIPTION
The L4960 is a monolithic power switching regula-tor delivering 2.5A at a voltage variable from 5V to 40V in step down configuration.
Features of the device include current limiting, soft start, thermal protection and 0 to 100% duty cycle f
老年人头晕是什么原因引起的or continuous operation mode.
June 2000
ORDERING NUMBERS : L4960 (Vertical) L4960H (Horizontal)
HEPTAWATT
BLOCK DIAGRAM
The L4960 is mounted in a Heptawatt plastic power package and requires very few external compo-nents.
Efficient operation at switching frequencies up to 150KHz allows a reduction in the size and cost of external filter components.
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PIN CONNECTION (Top view)
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N °NAME
FUNCTION
1
SUPPLY VOLTAGE
Unregulated voltage input. An internal regulator powers the
internal logic.
2FEEDBACK INPUT
孩童之道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.
3
FREQUENCY COMPENSATION A ries RC network connected between this terminal and ground determines the regulation loop gain characteristics.4GROUND Common ground terminal.
5
OSCILLATOR
A parallel RC network connected to this terminal determines the switching frequency.
6SOFT 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.阳痿早泄药酒
7OUTPUT
Regulator output.
PIN FUNCTIONS
Symbol Parameter
Value Unit V 1Input voltage
50V V 1 - V 7Input to output voltage difference 50V V 7Negative output DC voltage
-1V Negative output peak voltage at t = 0.1µs; f = 100KHz -5V V 3, V 6Voltage at pin 3 and 6 5.5V V 2Voltage at pin 27V I 3Pin 3 sink current 1mA I 5Pin 5 source current
一锅鲜的做法20mA P tot Power dissipation at T ca ≤ 90°C 15W T j , T stg
中国最穷的城市Junction and storage temperature
-40 to 150
°C
ABSOLUTE MAXIMUM RATINGS
Symbol
Parameter
Test Conditions
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 = 2.5A
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 2A 1030mV V ref Internal reference voltage (pin 2)
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 0.4
mV/°C V d Dropout voltage I o = 2A
1.4
3
V
I om Maximum operating load current
V i = 9V to 46V V o = V ref to 36V 2.5 A I 7L Current limiting threshold (pin 7)
V i = 9V to 46V V o = V ref to 36V
3 4.5A I SH Input average current V i = 46V; output short-circuit
30
哲学著作60
mA
ηEfficiency f = 100KHz V o = V ref 75 %
圆明园被毁I o = 2A V o = 12V
85 %SVR
Supply voltage ripple rejection
∆ V i = 2V rms fripple = 100Hz V o = V ref Io = 1A 50
56
dB
f Switchin
母子伦理电影
g frequency
85100115KHz ∆ 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 = 2A
120
150 KHz T sd
Thermal shutdown junction temperature
150
°C
ELECTRICAL CHARACTERISTICS (Refer to the test circuit, T j = 25 °C, V i = 35V, unless otherwi specified)
Symbol Parameter
Value Unit R th j-ca Thermal resistance junction-ca max 4 °C/W R th j-amb
Thermal resistance junction-ambient
max
50
°C/W
THERMAL DATA
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ELECTRICAL CHARACTERISTICS (continued)
Symbol Parameter Test Conditions Min.Typ.Max.Unit DC CHARACTERISTICS
3040mA I1Q Quiescent drain current100% duty cycle
pins 5 and 7 open
V i = 46V
0% duty cycle1520mA -I7L Output leakage current0% duty cycle1mA SOFT START
I6SO Source current100140180µA I6SI Sink current5070120µA ERROR AMPLIFIER
V3H High level output voltage V2 = 4.7V I3 = 100µA 3.5 V V3L Low level output voltage V2 = 5.3V I
3 = 100µA0.5V I3SI Sink output current V2 = 5.3V100150µA -I3SO Source output current V2 = 4.7V100150µA I2Input bias current V2 = 5.2V210µA
G v DC open loop gain V3 = 1V to 3V4655dB OSCILLATOR
-I5Oscillator source current5mA
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CIRCUIT OPERATION (refer to the block diagram)The L4960 is a monolithic stepdown switching regu-lator providing output voltages from 5.1V to 40V and delivering 2.5A.
The regulation loop consists of a sawtooth oscilla-tor, error amplifier, comparator and the output stage. An error signal is produced by comparing the output voltage with a preci 5.1V on-chip refer-ence (zener zap trimmed to ± 2%).
This error signal is then compared with 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 pin 3. Closing the loop directly gives an output voltage of 5.1V. 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 to 0.4V.
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 introduced by the soft start network. The thermal overload circuit dis-ables circuit operation when the junction tempera-ture reaches about 150°C and has hysteresis to
prevent unstable conditions.
Figure 1. Soft start waveforms
Figure 2. Current limiter waveforms
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