AME5177 Datasheet, PDF (7/14 Pages) Analog Microelectronics – Synchronous Boost Converter

AME
AME5177
n Detailed Description
The AME5177 is a high efficiency synchronous boost
converter, which is based on a hysteretic current control-
ler topology using synchronous rectification to obtain
maximum efficiency at minimal quiescent current condi-
tion. The converter allows the use of low cost chip induc-
tor (Support Inductor of Multilayer Type) and small ce-
ramic input and output capacitors total only three exter-
nal components.
Enable Function
The AME5177 has a dedicated enable pin. The device
is enabled when pull the EN above 0.8V. Furthermore,
the device is disabled when pull the EN below 0.4V.
Over Current Limit
The AME5177 provide the current limit protection func-
tion. When inductor current reaches the internal switch
current limit threshold, the internal switch will be turned
off. When the over current state is eliminated, the IC
resumes its nornal operation.
Over Temperature Protection
When the junction temperature exceeds 150^oC, the over
temperature protection circuit turns off the internal switch,
the converter will not turn back on until the device has
cooled approximately 20 degrees. For normal operation,
the junction temperature cannot exceed T_J=+125^oC.
Synchronous Boost Converter
With Low Quiescent Current
n Application Information
Inductor
The Inductor is required to supply energy to the load
while being driven by switched high side MOSFET.
Choose inductance that will affect the period proportional
to inductance. Therefore, choosing greater inductance
can improve system efficiency since the switching fre-
quency is decreased to reduce system switching losses.
Finally, the choice of which style inductor to utilize mainly
depends on the price vs. size requirements and any EMI
constraints. Suggesting the inductance range is from
10µH to 33µH.
Input Capacitor
Use low ESR capacitors for the best performance.
When using ceramic capacitors make sure that they have
enough capacitance to provide sufficient charge to pre-
vent excessive voltage ripple at input terminal. Further-
more, an input capacitor improves EMI problems in the
power supply circuit.
Output Capacitor
The output capacitor is required to place enough ca-
pacitance to improve the system efficiency and output
ripple. Ceramic capacitors are recommended. Low ESR
capacitors are preferred to keep the output voltage ripple
low. Furthermore, the output capacitance can be esti-
mated by:
C_OUT
≥
L
2
Where L is the inductance. The characteristics of the
output capacitor also affect the stability transient behav-
ior of the regulation system. The AME5177 can be opti-
mized for a wide range of capacitance and ESR values,
such as solid tantalum, ceramic, and aluminum electro-
lytic capacitors.
Rev. A.01
7