STMICROELECTRONICS L4960

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 regulator 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
for continuous operation mode.
HEPTAWATT
ORDERING NUMBERS: L4960 (Vertical)
L4960H (Horizontal)
The L4960 is mounted in a Heptawattplastic power
package and 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.
BLOCK DIAGRAM
June 2000
1/16
L4960
PIN CONNECTION (Top view)
ABSOLUTE MAXIMUM RATINGS
Symbol
V1
V1 - V7
V7
V3, V6
V2
I3
I5
Ptot
Tj, Tstg
Parameter
Input voltage
Input to output voltage difference
Negative output DC voltage
Negative output peak voltage at t = 0.1µs; f = 100KHz
Voltage at pin 3 and 6
Voltage at pin 2
Pin 3 sink current
Pin 5 source current
Power dissipation at Tcase ≤ 90°C
Junction and storage temperature
Value
50
50
-1
-5
5.5
7
1
20
15
-40 to 150
Unit
V
V
V
V
V
V
mA
mA
W
°C
PIN FUNCTIONS
FUNCTION
N°
NAME
1
SUPPLY VOLTAGE
Unregulated voltage input. An internal regulator powers the
internal logic.
2
FEEDBACK 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.
3
FREQUENCY
COMPENSATION
A series RC network connected between this terminal and
ground determines the regulation loop gain characteristics.
4
GROUND
Common ground terminal.
5
OSCILLATOR
A parallel RC network connected to this terminal determines the
switching frequency.
6
SOFT 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.
7
OUTPUT
Regulator output.
2/16
L4960
THERMAL DATA
Symbol
Parameter
Value
Unit
Rth j-case
Thermal resistance junction-case
max
4
°C/W
Rth j-amb
Thermal resistance junction-ambient
max
50
°C/W
ELECTRICAL CHARACTERISTICS (Refer to the test circuit, T j = 25 °C, Vi = 35V, unless otherwise
specified)
Symbol
Parameter
Test Conditions
Min.
Typ.
Max.
Unit
Vref
40
V
9
46
V
DYNAMIC CHARACTERISTICS
Vo
Output voltage range
Vi = 46V
Io = 1A
Vi
Input voltage range
Vo = Vref to 36V
Io = 2.5A
∆ Vo
Line regulation
Vi = 10V to 40V
∆ Vo
Load regulation
Vref
∆ Vref
∆T
Io = 1A
15
50
mV
Vo = Vref
Io = 0.5A to 2A
10
30
mV
Internal reference voltage
(pin 2)
Vi = 9V to 46V
Io = 1A
5.1
5.2
V
Average temperature
coefficient of refer voltage
Tj = 0°C to 125°C
Io = 1A
0.4
Vd
Dropout voltage
Io = 2A
1.4
Iom
Maximum operating load
current
Vi = 9V to 46V
Vo = Vref to 36V
I7L
Current limiting threshold
(pin 7)
Vi = 9V to 46V
Vo = Vref to 36V
ISH
Input average current
Vi = 46V;
Efficiency
η
SVR
Supply voltage ripple
rejection
Vo = Vref
5
mV/°C
3
2.5
V
A
3
4.5
A
60
mA
output short-circuit
30
f = 100KHz
Vo = Vref
75
%
Io = 2A
Vo = 12V
85
%
50
56
dB
85
100
∆ Vi = 2Vrms
fripple = 100Hz
Vo = Vref
f
Switching frequency
∆f
∆ Vi
Voltage stability of
switching frequency
Vi = 9V to 46V
∆f
∆ Tj
Temperature stability of
switching frequency
Tj = 0°C to 125°C
fmax
Maximum operating
switching frequency
Vo = Vref
Tsd
Thermal shutdown
junction temperature
Io = 1A
Io = 2A
120
115
KHz
0.5
%
1
%
150
KHz
150
°C
3/16
L4960
ELECTRICAL CHARACTERISTICS (continued)
Symbol
Parameter
Test Conditions
Min.
Typ.
Max.
Unit
30
40
mA
15
20
mA
1
mA
DC CHARACTERISTICS
I1Q
Quiescent drain current
100% duty cycle
pins 5 and 7 open
Vi = 46V
0% duty cycle
-I7L
Output leakage current
0% duty cycle
SOFT START
I6SO
Source current
100
140
180
µA
I6SI
Sink current
50
70
120
µA
ERROR AMPLIFIER
V3H
High level output voltage
V2 = 4.7V
I3 = 100µA
V3L
Low level output voltage
V2 = 5.3V
I3 = 100µA
I3SI
Sink output current
V2 = 5.3V
100
150
µA
Source output current
V2 = 4.7V
100
150
µA
I2
Input bias current
V2 = 5.2V
Gv
DC open loop gain
V3 = 1V to 3V
-I3SO
3.5
V
0.5
2
46
55
10
V
µA
dB
OSCILLATOR
-I5
4/16
Oscillator source current
5
mA
L4960
CIRCUIT OPERATION (refer to the block diagram)
The L4960 is a monolithicstepdownswitching regulator providing outputvoltagesfrom 5.1V to 40V and
delivering 2.5A.
The regulation loop consists of a sawtooth oscillator, error amplifier, comparator and the output
stage. An errorsignal is produced by comparing the
output voltage with a precise 5.1V on-chip reference (zener zap trimmed to ± 2%).
This error signalis thencompared with thesawtooth
signal to generate the fixed frequency pulse width
modulated pulses 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
inserting 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 Css and
allowed to rise, linearly, as this capacitor is charged
by a constant current source. Output overload protection is provided in the form of a current limiter.
The load current is sensed by an internal metal
resistor connected to a comparator. When the load
current exceeds a preset threshold this comparator
sets a flip flop which disables the output stage and
discharges the soft start capacitor. A second comparator resets 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 rises under control of the soft start network.
If the overload condition is still present 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 disables circuit operation when the junction temperature reaches about 150°C and has hysteresis to
prevent unstable conditions.
Figure 1. Soft start waveforms
Figure 2. Current limiter waveforms
5/16
L4960
Figure 3. Test and application circuit
C6, C7: EKR (ROE)
L1 = 150µH at 5A (COGEMA 946042)
CORE TYPE: MAGNETICS 58206-A2 MPP
N° TURNS 45, WIRE GAUGE: 0.8mm (20 AWG)
Figure 4. Quiescent drain
current vs. supply voltage (0%
duty cycle)
6/16
Figure 5. Quiescent drain
current vs. supply voltage
(100% duty cycle)
Figure 6. Quiescent drain
curre nt vs. junction te mperature (0% duty cycle)
L4960
Figure 7. Quiescent drain
current vs. junction te mperature (100% duty cycle)
Figure 8. Reference voltage
(pin 2) vs. Vi
Figure 9. Reference voltage
versus junction temperature
(pin 2)
Figure 10. Open loop frequency and phase responde
of error amplifier
F igur e 11. Sw itchi ng frequency vs. input voltage
Fi gure 12. Switc hi ng frequ en cy vs . j unctio n temperature
F igure 13. Sw itching fr equency vs. R2 (see test circuit)
F igur e 14. Lin e tr ansient
response
Figure 15. Load transi ent
response
7/16
L4960
Figure 16. Supply voltage
ripple rejection vs. frequency
Figure 17. Dropout voltage
between pin 1 and pin 7 vs.
current at pin 7
Figure 18. Dropout voltage
be twee n pin 1 an d 7 v s.
junction temperature
Figure 19. Power dissipation
derating curve
F i gur e 2 0. Effici enc y vs.
output current
Fi g ure 21 . Effi cie nc y v s.
output current
F ig ure 22 . E ffi c ien cy vs .
output current
8/16
Fi g ure 2 3. E ffi cie ncy v s.
output voltage
L4960
APPLICATION INFORMATION
Figure 24. Typical application circuit
C 1, C 6, C 7: EKR (ROE)
D 1: BYW80 OR 5A SCHOTTKY DIODE
SUGGESTED INDUCTOR: L1 = 150µH at 5A
CORE TYPE: MAGNETICS 58206 - A2 - MPP
N° TURNS: 45, WIRE GAUGE: 0.8mm (20 AWG), COGEMA 946042
U15/GUP15: N° TURNS: 60, WIRE GAUGE: 0.8mm (20 AWG), AIR GAP: 1mm, COGEMA 969051.
Figure 25. P.C. board and component layout of
the Fig. 24 (1 : 1 scale)
Resistor values for
standard output voltages
Vo
R3
R4
12V
15V
18V
24V
4.7KΩ
4.7KΩ
4.7KΩ
4.7KΩ
6.2KΩ
9.1KΩ
12KΩ
18KΩ
9/16
L4960
APPLICATION INFORMATION
Figure 26. A minimal 5.1V fixed regulator; Very few component are required
*
COGEMA 946042
969051
** EKR (ROE)
(TOROID CORE)
(U15 CORE)
Figure 27. Programmable power supply
Vo = 5.1V to 15V
Io = 2.5A max
Load regulation (1A to 2A) = 10mV (Vo = 5.1V)
10/16
L4960
APPLICATION INFORMATION (continued)
Figure 28. Microcomputer supply with + 5.1V, -5V, +12V and -12V outputs
11/16
L4960
APPLICATION INFORMATION (continued)
Figure 29. DC-DC converter 5.1V/4A, ± 12V/2.5A;a suggestion how to synchronize a negative output
L1, L3 = COGEMA 946042 (969051)
L2 = COGEMA 946044 (946045)
D1, D2, D 3 = BYW80
Figure 30. - In multiple supplies several L4960s can be synchronized as shown
12/16
L4960
APPLICATION INFORMATION (continued)
Figure 31. Regulator for distributed supplies
MOUNTING INSTRUCTION
The powerdissipated in the circuitmust be removed
by adding an external heatsink.
Thanks to the Heptawatt package attaching the
hetsink is very simple, a screw or a compression
spring (clip) being sufficient. Between the heatsink
and the packageit is betterto insert a layer of silicon
grease, to optimize the thermal contact, no electrical isolation is needed between the two surfaces.
Figure 32. Mounting example
13/16
L4960
DIM.
A
C
D
D1
E
E1
F
F1
G
G1
G2
H2
H3
L
L1
L2
L3
L4
L5
L6
L7
L9
M
M1
V4
Dia
MIN.
mm
TYP.
2.4
1.2
0.35
0.7
0.6
2.34
4.88
7.42
10.05
16.7
21.24
22.27
2.6
15.1
6
2.55
4.83
2.54
5.08
7.62
16.9
14.92
21.54
22.52
2.8
15.5
6.35
0.2
2.8
5.08
3.65
MAX.
4.8
1.37
2.8
1.35
0.55
0.97
0.8
0.9
2.74
5.28
7.82
10.4
10.4
17.1
inch
TYP.
MIN.
0.094
0.047
0.014
0.028
0.024
0.095
0.193
0.295
0.396
0.657
21.84
22.77
1.29
3
15.8
6.6
0.386
0.877
0.102
0.594
0.236
3.05
5.33
40°
3.85
0.100
0.190
(typ.)
0.144
0.100
0.200
0.300
0.668
0.587
0.848
0.891
0.110
0.610
0.250
0.008
0.110
0.200
OUTLINE AND
MECHANICAL DATA
MAX.
0.189
0.054
0.110
0.053
0.022
0.038
0.031
0.035
0.105
0.205
0.307
0.409
0.409
0.673
0.860
0.896
0.051
0.118
0.622
0.260
0.120
0.210
Heptawatt V
0.152
V
L
V
E
L1
M1
A
M
D
C
D1
L5
H2
L2
L3
F
E
E1
V4
L9
H3
H1
G
G1
G2
Dia.
F
L7
L4
L6
14/16
H2
F1
HEPTAMEC
L4960
DIM.
mm
MIN.
TYP.
inch
MAX.
A
4.8
C
1.37
D
MIN.
TYP.
MAX.
0.189
0.054
2.4
2.8
0.094
0.110
D1
1.2
1.35
0.047
0.053
E
0.35
0.55
0.014
0.022
F
0.6
0.8
0.024
0.031
F1
0.9
0.035
G
2.41
2.54
2.67
0.095
0.100
0.105
G1
4.91
5.08
5.21
0.193
0.200
0.205
G2
7.49
7.62
7.8
0.295
0.300
0.307
H2
H3
10.4
10.05
10.4
0.409
0.396
0.409
L
14.2
0.559
L1
4.4
0.173
L2
15.8
0.622
L3
5.1
0.201
L5
2.6
3
0.102
0.118
L6
15.1
15.8
0.594
0.622
L7
6
6.6
0.236
L9
Dia
4.44
3.65
OUTLINE AND
MECHANICAL DATA
0.260
Heptawatt H
0.175
3.85
0.144
0.152
15/16
L4960
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