ame5130 AME, Inc., ame5130 Datasheet - Page 7

• Manufacturer Part Number: ame5130
• Description: Micropower Step-up Dc/dc Converter
• Manufacturer: AME, Inc.

n Electrical Specifications
AME5130
scheme. Operation can be best understood by referring
to Figure 3. When the voltage at the FB pin is less than
1.23V, the Enable Comp in Figure 3 enables the device
and the NMOS switch is turmed on pulling the SW pin to
ground. When the NMOS switch is on, current is sup-
plied by the output capacitor C
the inductor reaches the peak current limit, the 400ns
One Shot turns off the NMOS switch. The SW voltage
will then rise to the output voltage plus a diode drop and
the inductor current will begin to decrease as shown in
Figure 3. During this time the energy stored in the induc-
tor is transferred to C
off-time the NMOS switch is turned on and energy is
stored in the inductor again. This energy transfer from
the inductor to the output causes a stepping effect in
the output ripple.
1.23V. When FB reaches this voltage, the enable com-
parator then disables the device turning off the NMOS
switch and reducing the Iq of the device to 64 A. The
load current is then supplied solely by C
by the gradually decreasing slope at the output. When
the FB pin drops slightly below 1.23V, the enable com-
parator enables the device and begins the cycle de-
scribed previously. The EN pin can be used to turn off
the AME5130 and reduce the Iq to 0.01 A. In shutdown
mode the output voltage will be a diode drop lower than
the input voltage.
The AME5130 features a constant off-time control
This cycle is continued until the voltage at FB reaches
AME, Inc.
OUT
and the load. After the 400ns
OUT
. Once the current in
OUT
indicated
n Application Information
calculated using the following equation:
switch current limit found in the Typical Performance Char-
acteristics section, and T
using this equation be sure to use in minimum input volt-
age for the application, such as for battery powered ap-
plications.
lossed and increase efficiency.
applications that require an input voltage that approaches
the output voltage, such as when converting a Li-ion bat-
tery voltage to 5V, the 400ns off time may not be enough
time to discharge the energy in the inductor and transfer
the energy to the output capacitor and load. This can
cause a ramping effect in the inductor current waveform
and an increased ripple on the output voltage. Using a
smaller inductor will cause the I
increase the output voltage ripple further. This can be
solved by adding a 4.7pF capacitor across the R1 feed-
back resistor (Figure 3) and slightly increasing the out-
put capacitor. A smaller inductor can then be used to
ensure proper discharge in the 400ns off time.
of the schottky diode should be larger than the peak in-
ductor current, I
drop and fast switching speeds are ideal for increasing
efficiency in portable applications. Choose a reverse break-
down of the schottky diode larger than the output volt-
age.
INDUCTOR SELECTION
The appropriate inductor for a given application is
Care should be taken when choosing an inductor. For
DIODE SELECTION
To maintain high efficiency, the average current rating
Where V
Choosing inductors with low ESR decrease power
L
D
V
OUT
is the schottky diode voltage, I
PK
. Schottky diodes with a low forward
V
Micropower Step-Up
I
CL
IN(min)
DC/DC Converter
OFF
is the switch off time. When
V
D
PK
T
to increase and will
OFF
CL
is the
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