ADP3310AR-3 データシートの表示（PDF） - Analog Devices
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ADP3310AR-3 Datasheet PDF : 8 Pages
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ADP3310
Current Limit Threshold Voltage = 0.05 V
Safety Factor = 1.5
IO = Output Current
RS is not needed in circuits that do not require current limiting.
In that case, the IS pin must be tied to the input pin.
The simplest and cheapest sense resistor for high current applica-
tions, (i.e., Figure 1) is a PCB trace. The temperature depen-
dence of the copper trace and the thickness tolerances of the
trace must be taken into account in the design. The resistivity of
copper has a positive temperature coefficient of +0.39%/°C.
Copper’s Tempco in conjunction with the proportional-to-
absolute temperature (PTAT) current limit voltage can provide
an accurate current limit. Table II provides the resistance value
for PCB copper traces. Alternately, an appropriate sense resistor
such as surface mount sense resistors available from KRL can be
used.
PCB-Layout Issues
For optimum voltage regulation, place the load as close as pos-
sible to the device’s VOUT and GND pins. It is recommended to
use dedicated PCB traces to connect the MOSFET’s drain to
the positive terminal and GND to the negative terminal of the
load to avoid voltage drops along the high current carrying PCB
traces.
Application Circuits
Typical 3 A LDO Circuit
The ADP3310 and a power MOSFET can be used to power the
new generation of CPUs and microprocessors from the standard
+5 V supply at a very low cost (Figure 14). This circuit provides
low dropout, fast switching and high switching load current
from 0 A to 3 A. Due to the high switching load current, capaci-
tors with high ripple current carrying capability, such as OSCON
or special tantalum capacitors from Sprague (593D), are recom-
mended for the output.
Table II. Printed Circuit Copper Resistance
Conductor
Thickness
1/2 oz/ft2
(18 µm)
1 oz/ft2
(35 µm)
2 oz/ft2
(70 µm)
3 oz/ft2
(106 µm)
Conductor Width
In
0.025
0.050
0.100
0.200
0.500
0.025
0.050
50mV/d0i.v100
0.200
0.500
2V/div
0.025
0.050
0.100
0.200
0.500
0.025
0.050
0.100
0.200
0.500
Resistance
mΩ/In
39.3
19.7
9.83
4.91
1.97
19.7
9.83
5µs/di4v.91
2.46
0.98
9.83
4.91
2.46
1.23
0.49
6.5
3.25
1.63
0.81
0.325
4.5V TO 5.5V
220F +
OSCON
10F
1k⍀
R2
0.011⍀
M1
NDP6020P
IS
VIN
GATE
ADP3310-3.3
EN
VOUT
GND
10F
3.3V
3 ؋ 220F
OSCON
Figure 14. Typical 3 A Low Dropout Regulator Circuit
VIN = 5V TO 15V
OSCON
220F +
CIN
C1
1F
** COILTRONICS CTX-68-4
** KRL SL-1-C1-ORO5OL
RC
1k⍀
CC
22nF
C2
10nF
VIN
P-DRIVE
INT VCC
SD
ADP1148
SENSE+
ITH SENSE–
CT
470pF
CT N-DRIVE
FB
S-GND P-GND
IRF7204
L*
68µH
RSENSE** OSCON
0.1⍀ 220F
C3
C4
1nF
R1
30.1k⍀
1%
N-CH
IRF7403
D1
10BQ040
2N3906
Q1
R2
124k⍀
1%
MI
IRF7404
IS GATE
IN
OUT
ADP3310-3.3
EN GND
2N3906
Q2
BAT54
3.3V/1A
C5
10F
R3
274k⍀
Figure 15. High Current Post Regulator with SOIC PMOS
REV. A
–7–
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