STMICROELECTRONICS L4962_00

L4962
®
1.5A POWER SWITCHING REGULATOR
1.5A OUTPUT CURRENT
5.1V TO 40V OUTPUT 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 L4962 is a monolithic power switching regulator delivering 1.5A 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 operating mode.
POWERDIP
(12 + 2 + 2)
HEPTAWATT
ORDERING NUMBERS : L4962/A (12 + 2 + 2 Powerdip)
L4962E/A (Heptawatt
Vertical)
L4962EH/A (Horizontal
Heptawatt)
The L4962 is mounted in a 16-lead Powerdip plastic
package and Heptawatt 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
Pin X = Powerdip
Pin (X) = Heptawatt
June 2000
1/16
L4962
ABSOLUTE MAXIMUM RATINGS
Symbol
V7
V7 - V2
V2
V11, V15
Parameter
Value
Unit
Input voltage
50
V
Input to output voltage difference
50
V
Negative output DC voltage
-1
V
Output peak voltage at t = 0.1µs; f = 100KHz
-5
V
Voltage at pin 11, 15
5.5
V
V10
Voltage at pin 10
7
V
I11
Pin 11 sink current
1
mA
I14
Pin 14 source current
20
mA
Ptot
Power dissipation at Tpins ≤ 90°C (Powerdip)
Tcase ≤ 90°C (Heptawatt)
4.3
15
W
W
-40 to 150
°C
Tj, Tstg
Junction and storage temperature
PIN CONNECTION (Top view)
THERMAL DATA
Symbol
Rth j-case
Rth j-pins
Rth j-amb
Parameter
Thermal resistance junction-case
Thermal resistance junction-pins
Thermal resistance junction-ambient
max
max
max
Heptawatt
Powerdip
4°C/W
50°C/W
14°C/W
80°C/W*
* Obtained with the GND pins soldered to printed circuit with minimized copper area.
PIN FUNCTIONS
HEPTAWATT
POWERDIP
NAME
FUNCTION
1
7
SUPPLY VOLTAGE
Unregulated voltage input. An internal regulator powers
the internal logic.
2
10
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
11
FREQUENCY
COMPENSATION
A series RC network connected between this terminal
and ground determines the regulation loop gain
characteristics.
2/16
L4962
PIN FUNCTIONS (cont’d)
HEPTAWATT
POWERDIP
4
4, 5, 12, 13
5
FUNCTION
NAME
GROUND
Common ground terminal.
14
OSCILLATOR
A parallel RC network connected to this terminal
determines the switching frequency. This pin must be
connected to pin 7 input when the internal oscillator is
used.
6
15
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
2
OUTPUT
Regulator output.
1, 3, 6,
8, 9, 16
N.C.
ELECTRICAL CHARACTERISTICS (Refer to the test circuit, Tj = 25 °C, Vi = 35V, unless otherwise
specified)
Symbol
Parameter
Test Conditions
Min.
Typ.
Max.
Unit
Vref
40
V
9
46
V
15
50
mV
8
20
mV
5.1
5.2
V
DYNAMIC CHARACTERISTICS
Vo
Output voltage range
Vi = 46V
Io = 1A
Vi
Input voltage range
Vo = Vref to 36V
Io = 1.5A
∆ Vo
Line regulation
Vi = 10V to 40V
∆ Vo
Load regulation
Vo = Vref
Io = 0.5A to 1.5A
Vref
Internal reference voltage
(pin 10)
Vi = 9V to 46V
Io = 1A
∆ Vref
∆T
Average temperature
coefficient of refer. voltage
Tj = 0°C to 125°C
Io = 1A
0.4
Vd
Dropout voltage
Io = 1.5A
1.5
Iom
Maximum operating load
current
Vi = 9V to 46V
Vo = Vref to 36V
1.5
I2L
Current limiting threshold
(pin 2)
Vi = 9V to 46V
Vo = Vref to 36V
2
ISH
Input average current
Vi = 46V;
Efficiency
η
SVR
Supply voltage ripple
rejection
Vo = Vref
Io = 1A
5
mV/°C
2
V
A
3.3
A
30
mA
output short-circuit
15
f = 100KHz
Vo = Vref
70
%
Io = 1A
Vo = 12V
80
%
56
dB
∆ Vi = 2Vrms
fripple = 100Hz
Vo = Vref
50
Io = 1A
3/16
L4962
ELECTRICAL CHARACTERISTICS (continued)
Symbol
Parameter
Test Conditions
Min.
Typ.
Max.
Unit
85
100
115
KHz
DYNAMIC CHARACTERISTICS (cont’d)
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
120
0.5
%
1
%
150
KHz
150
°C
DC CHARACTERISTICS
I7Q
Quiescent drain current
100% duty cycle
pins 2 and 14 open
30
40
mA
15
20
mA
1
mA
Vi = 46V
0% duty cycle
-I2L
Output leakage current
0% duty cycle
SOFT START
I15SO
Source current
100
140
180
µA
I15SI
Sink current
50
70
120
µA
ERROR AMPLIFIER
V11H
High level output voltage
V10 = 4.7V
I11 = 100µA
V11L
Low level output voltage
V10 = 5.3V
I11 = 100µA
I11SI
Sink output current
V10 = 5.3V
100
150
µA
Source output current
V10 = 4.7V
100
150
µA
I10
Input bias current
V10 = 5.2V
Gv
DC open loop gain
V11 = 1V to 3V
-I11SO
3.5
V
0.5
2
46
55
10
V
µA
dB
OSCILLATOR
-I14
4/16
Oscillator source current
5
mA
L4962
CIRCUIT OPERATION (refer to the block diagram)
The L4962 is a monolithic stepdown switching regulator providing output voltages from 5.1V to 40V and
delivering 1.5A.
The regulation loop consists of a sawtooth oscillator, error amplifier, comparator and the output
stage. An error signal is produced by comparing the
output voltage with a precise 5.1V on-chip reference (zener zap trimmed to ± 2%).
This error signal is then compared with the sawtooth
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 11. 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
L4962
Figure 3. Test and application circuit (Powerdip)
1) D1: BYW98 or 3A Schottky diode, 45V of VRRM;
2) L1: CORE TYPE - MAGNETICS 58120 - A2 MPP
N° TURNS 45, WIRE GAUGE: 0.8mm (20 AWG)
3) C6, C7: ROE, EKR 220µF 40V
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
current vs. junction temperature (0% duty cycle)
L4962
Figure 7. Quiescent drain
current vs. junction temperature (100% duty cycle)
Figure 8. Reference voltage
(pin 10) vs. Vi rdip) vs. Vi
Figure 9. Reference voltage
(pin 10 ) vs. junction temperature
Figure 10. Open loop frequency and phase re- sponse
of error amplifier
Figure 11. Switching frequency vs. input voltage
Figure 12. Switching frequency vs. junction temperature
Figure 13. Switching frequency vs. R2 (see test circuit)
Figure 14. Line transient
response
Figure 15. Load transient
response
7/16
L4962
Figure 16. Supply voltage
ripple rejection vs. frequency
Figure 17. Dropout voltage
between pin 7 and pin 2 vs.
current at pin 2
Figure 18. Dropout voltage
between pin 7 and 2 vs.
junction temperature
Fig ure 19. Effi ciency vs.
output current
Fi gure 20. Effici ency vs.
output current
Fi gure 21 . Effi ciency vs.
output current
F igu re 22. Effi ciency vs.
output voltage
Fi gure 23. Effici ency vs.
output voltage
Figure 24. Maximum allowable power dissipation vs. ambient temperature (Powerdip)
8/16
L4962
APPLICATION INFORMATION
Figure 25. Typical application circuit
C1, C6, C7: EKR (ROE)
D1: BYW98 OR VISK340 (SCHOTTKY)
SUGGESTED INDUCTORS: (L1) = MAGNETICS 58120 - A2MPP - 45 TURNS - WIRE GAUGE 0.8mm (20AWG)
COGEMA 946043
OR U15, GUP15, 60 TURNS 1mm, AIR GAP 0.8mm (20 AWG) - COGEMA 969051.
Figure 26. P.C. board and component layout of the circuit of Fig. 25 (1 : 1 scale)
Resistor values for
standard output 7 voltages
Vo
R3
R4
12V
15V
18V
24V
4.7KΩ
4.7KΩ
4.7KΩ
4.7KΩ
6.2KΩ
9.1KΩ
12KΩ
18KΩ
9/16
L4962
APPLICATION INFORMATION (continued)
Figure 27. - A minimal 5.1V fixed regulator; Very few component are required
*
COGEMA 946043 (TOROID CORE)
969051 (U15 CORE)
** EKR (ROE)
Figure 28. Programmable power supply
Vo = 5.1V to 15V
Io = 1.5A max
Load regulation (0.5A to 1.5A) = 10mV (Vo = 5.1V)
Line regulation (220V ± 15% and to Io = 1A) = 15mV (Vo = 5.1V)
10/16
L4962
APPLICATION INFORMATION (continued)
Figure 29. DC-DC converter 5.1V/4A, ± 12V/1A. A suggestion how to synchronize a negative output
L1, L3 = COGEMA 946043 (969051)
L2 = COGEMA 946044 (946045)
Figure 30. In multiple supplies several
L4962s can be synchronized as shown
Figure 31. Preregulator for distributed supplies
* L2 and C2 are necessary to reduce the switching frequency spikes
when linear regulators are remote from L4962
11/16
L4962
MOUNTING INSTRUCTION
The Rth-j-amb of the L4962 can be reduced by
soldering the GND pins to a suitable copper area of
the printed circuit board (Fig. 32).
The diagram of figure 33 shows the Rth-j-amb as a
function of the side "l" of two equal square copper
areas having the thickness of 35µ (1.4 mils). During
soldering the pins temperature must not exceed
260°C and the soldering time must not be longer
than 12 seconds.
The external heatsink or printed circuit copper are
must be connected to electrical ground.
Figure 32. Example of P.C. board copper area which is used
as heatsink
12/16
Figure 33. Maximum dissipable
power and junction to ambient
thermal resistance vs. side "l"
L4962
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
20.0
0.787
E
8.80
0.346
e
2.54
0.100
e3
17.78
0.700
F
7.10
0.280
I
5.10
0.201
L
OUTLINE AND
MECHANICAL DATA
3.30
0.130
Powerdip 16
Z
1.27
0.050
13/16
L4962
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
21.84
22.77
1.29
3
15.8
6.6
inch
TYP.
MIN.
0.094
0.047
0.014
0.028
0.024
0.095
0.193
0.295
0.396
0.657
0.386
0.877
0.102
0.594
0.236
3.05 0.100
5.33 0.190
40˚ (typ.)
3.85 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
H2
L2
L5
L3
F
E
E1
V4
L9
H3
G
H1
G1
G2
Dia.
F
L4
L7
L6
14/16
H2
F1
HEPTAMEC
L4962
mm
DIM.
MIN.
TYP.
inch
MAX.
A
4.8
C
1.37
MIN.
TYP.
MAX.
0.189
0.054
D
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
0.260
Heptawatt H
0.175
3.85
OUTLINE AND
MECHANICAL DATA
0.144
0.152
15/16
L4962
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