
ML4865
PRODUCT SPECIFICATION
6
REV. 1.0.2 8/10/01
Figure 4. Output Current vs. Input Voltage
Figure 5. Efficiency vs. Output Current
Figure 6. No Load Input Current vs.
Input Voltage for the Circuit of Figure 7
The curves and the equations are based on the operating
circuit shown in Figure 7. It is recommended to verify the
current capability and efficiency for the components
selected.
Figure 7. Typical Application Circuit
Inductor Selection
The ML4865 is able to operate over a wide range of inductor
values. A value of 22μH or 33μH is a good choice, but any
value between 15μH and 50μH is acceptable. As the inductor
value is changed the control circuitry will automatically
adjust to keep the inductor current under control. Choosing
an inductance value of less than 15μH will reduce the com-
ponent’s footprint, but the efficiency and maximum output
current may drop.
It is important to use an inductor that is rated to handle 1.5A
peak currents without saturating. Also look for an inductor
with low winding resistance. A good rule of thumb is to
allow 5 to 10m
of resistance for each μH of inductance.
The final selection of the inductor will be based on trade-offs
between size, cost and efficiency. Inductor tolerance, core
and copper loss will vary with the type of inductor selected
and should be evaluated with a ML4865 under worst case
conditions to determine its suitability.
Several manufacturers supply standard inductance values in
surface mount packages:
Coilcraft
(847) 639-6400
Coiltronics
(561) 241-7876
Dale
(605) 665-9301
Sumida
(847) 956-0666
Output Capacitor
The output capacitor filters the pulses of current from the
switching regulator. Since the switching frequency will vary
with inductance, the minimum output capacitance required
to reduce the output ripple to an acceptable level will be a
function of the inductor used. Therefore, to maintain an out-
put voltage with less than 100mV of ripple (due to capaci-
tance) at full load current, use the following equation:
900
700
500
300
100
0
I
VIN (V)
0
4
8
10
2
6
WITH
EXTERNAL
SCHOTTKY
WITHOUT
EXTERNAL
SCHOTTKY
100
90
80
70
60
50
E
IOUT (mA)
1
10
100
1000
VOUT = 12V
with Schottky
without Schottky
VIN = 2V
VIN = 5V
VIN = 10V
300
250
200
150
100
50
0
I
VIN (V)
0
4
6
10
8
2
WITH
EXTERNAL
SCHOTTKY
WITHOUT
EXTERNAL
SCHOTTKY
ML4865
D1
MBR0520L
VOUT
C2
47
μ
F
R1
1M
C1
47
μ
F
VIN
22
μ
H
(Sumida CD75)
SENSE
GND
VIN
VL1
VOUT
SHDN
VL2
PWR GND
C
(F)
L
V
OUT
OUT
=
×
10
(2)