DN232 - SOT-23 Switching Regulator with Integrated 1A Switch Delivers High Current Outputs in a Small Footprint

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SOT-23 Switching Regulator with Integrated 1A Switch Delivers
High Current Outputs in a Small Footprint – Design Note 232
Albert Wu
5V Local Supply
Figure 1 shows a typical 3.3V to 5V boost converter
using the LT1930. The circuit can provide an impressive output current of 480mA while occupying less
than 0.3" by 0.35" of board area (less than 0.105 in2).
The efficiency, shown in Figure 2, remains above 83%
over a wide load current range of 60mA to 450mA,
reaching 86% at 200mA. The maximum output voltage
ripple of this circuit is 40mVP-P, which corresponds
to less than 1% of the nominal 5V output. Figure 3 is
an oscillograph of the transient response. The lower
waveform depicts a load step from 200mA to 300mA,
the middle waveform shows the inductor current and
the upper waveform shows the output voltage. The
output voltage remains within 1% of the nominal value
during the transient steps and displays a nice damped
response with little ringing.
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06/00/232_conv
L1
5.6μH
VIN
3.3V
C1
4.7μF
D1
5
1
VIN
SW
VOUT
5V
480mA
R1
40.2k
LT1930
OFF ON
4
SHDN
FB
C2
10μF
3
R2
13.3k
GND
2
C1: TAIYO-YUDEN X5R JMK212BJ475MG www.t-yuden.com
C2: TAIYO-YUDEN X5R JMK316BJ106ML
D1: ON SEMICONDUCTOR MBR0520 www.onsemi.com
L1: SUMIDA CR43-5R6 www.sumida.com
DN232 F01
Figure 1. 3.3V to 5V Boost Converter
90
VIN = 3.3V
85
80
EFFICIENCY (%)
Linear Technology’s LT®1930 is the industry’s highest
power SOT-23 switching regulator. The device contains
an internal 1A, 36V switch and is pin compatible with
both the low power LT1613 and the micropower LT1615.
The LT1930 provides a simple upgrade path for users of
these parts who need more power for new designs. In
addition to portable applications requiring higher output
currents, the device also fits well in nonbattery-operated
equipment. Multiple output power supplies can now use
a separate regulator for each output voltage, replacing
cumbersome quasi-regulated approaches using a single
regulator and custom transformers. The LT1930 utilizes
a constant frequency, internally compensated, current
mode PWM architecture that results in low, predictable
output noise that is easy to filter. Its 1.2MHz switching
frequency allows the use of tiny, low cost capacitors
and low profile inductors. With an input voltage range
of 2.6V to 16V, the LT1930 is a good fit for a variety
of applications.
VIN = 2.6V
75
70
65
60
55
50
0
100
200
400
300
LOAD CURRENT (mA)
500
DN232 F02
Figure 2. 3.3V to 5V Boost Converter Efficiency
VOUT
0.1V/DIV
AC COUPLED
IL1
0.5A/DIV
AC COUPLED
LOAD 300mA
CURRENT 200mA
20μs/DIV
DN232 F03
Figure 3. 3.3V to 5V Boost Converter Transient Response
12V Local Supply
Another typical application is a 5V to 12V boost converter
as shown in Figure 4. This circuit can provide 300mA of
output current and achieves efficiencies of up to 87%
as shown in Figure 5. The maximum output voltage
ripple of this circuit is 60mVP-P, which corresponds to
0.05% of the nominal 12V output. As seen in Figure 6,
the output voltage remains within 1% of the nominal
value during a 50mA load step.
L1
10μH
VIN
5V
D1
5
VIN
C1
2.2μF
SW
R1
115k
LT1930
4
OFF ON
VOUT
12V
300mA
1
SHDN
FB
±15V Dual Output Converter with Output
Disconnect
A ±15V dual output converter using the LT1930 is shown
in Figure 7. Both outputs are developed using charge
pumps, so both are disconnected from the input when
the LT1930 is turned off. Since the supplies are generated in the same manner, this circuit features excellent
cross regulation. For a 5× difference in output currents,
the positive and negative output voltages differ less
than 1%; for a 10× difference, they differ less than
2%. Both outputs of this circuit can each supply up to
70mA of current. The efficiency plot for this circuit is
shown in Figure 8.
C2
4.7μF
3
2
C1: TAIYO-YUDEN X5R LMK212BJ225MG (408) 573-4150
C2: TAIYO-YUDEN X5R EMK316BJ475ML
D1: ON SEMICONDUCTOR MBR0520 (800) 282-9855
L1: SUMIDA CR43-100 (874) 956-0666
DN232 F04
C4
1μF
L1
3.3μH
VIN
5V
R2
13.3k
GND
5
OFF ON
15V
70mA
1
C5
1μF
SW
VIN
C1
2.2μF
D1
R1
147k
LT1930
4
D2
SHDN
FB
C2
2.2μF
3
R2
13.3k
GND
2
Figure 4. 5V to 12V Boost Converter
90
VIN = 5V
85
DN232 F07
–15V
70mA
VIN = 3.3V
80
EFFICIENCY (%)
C6
2.2μF
C1: TAIYO-YUDEN X5R LMK212BJ225MG
D3 D4
C2, C3: TAIYO-YUDEN X5R EMK316BJ225ML
C4, C5: TAIYO-YUDEN X5R TMK316BJ105ML
(408) 573-4150
D1 TO D4: ON SEMICONDUCTOR MBR0520 (800) 282-9855
L1: SUMIDA CR43-3R3 (874) 956-0666
Figure 7. ±15V Dual Output Converter
with Output Disconnect
75
70
65
85
60
VIN = 5V
80
55
0
100
200
EFFICIENCY (%)
75
50
300
LOAD CURRENT (mA)
DN232 F05
Figure 5. 5V to 12V Boost Converter Efficiency
70
65
60
55
50
VOUT
0.2V/DIV
AC COUPLED
0
20
40
60
80
LOAD CURRENT (mA)
DN232 F08
IL1
0.5A/DIV
AC COUPLED
Figure 8. ±15V Dual Output Converter Efficiency
LOAD 250mA
CURRENT 200mA
20μs/DIV
DN232 F06
Figure 6. 5V to 12V Boost Converter Transient Response
Data Sheet Download
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