TS2576CM5-12 TSC [Taiwan Semiconductor Company, Ltd], TS2576CM5-12 Datasheet - Page 5

• Manufacturer Part Number: TS2576CM5-12
• Description: 3A Step Down Switching Voltage Regulator
• Manufacturer: TSC [Taiwan Semiconductor Company, Ltd]

TS2576
Application Information
It is required that VIN must be bypassed with at least a
100µF electrolytic capacitor for stability. Also, it is
strongly recommended the capacitor’s leads must be
dept short, and located near the regulator as possible.
For low operating temperature range, for example, below
-25
This is due to the reason that the capacitance value of
electrolytic capacitors decreases and the ESR increases
with lower temperatures and ago. Paralleling a ceramic
or solid tantalum capacitor will increase the regulator
stability at cold temperatures.
Output Capacitor
An output capacitor is also required to filter the output
voltage and is needed for loop stability. The capacitor
should be located near the TS2576 using short PC
board
recommended for low output ripple voltage and good
stability. Generally, low value or low voltage (less than
12V) electrolytic capacitors usually have higher ESR
numbers, For example, the lower capacitor values
(220µF - 1000µF) will yield typically 50mV to 150mV of
output ripple voltage, while larger-value capacitors will
reduce the ripple to approximately 20mV to 50mV.
The amount of output ripple voltage is primarily a
function of the ESR (Equivalent Series Resistance) of
the output capacitor and the amplitude of the inductor
ripple current ( I
Output Ripple Voltage = ( I
Some
“low-inductance”, or “low-ESR” are recommended to use
to further reduce the output ripple voltage to 10mV or
20mV. However, very low ESR capacitors, such as
tantalum capacitors, should be carefully evaluated.
Catch Diode
This diode is required to return path for the inductor
current when the switch is off. It should be located close
to the TS2576 using short leads and short printed circuit
traces as possible.
To satisfy the need to fast switching speed and low
forward voltage drop, Schottky diodes are widely used to
provide the best efficiency, especially in low output
voltage switching regulators (less than 5V). Beside,
Fast-Recovery, high-efficiency, or ultra fast recovery
diodes are also suitable. But some types with an abrupt
turn-off characteristic may cause instability and EMI
problems. A fast recovery diode with soft recovery
characteristics is better choice.
o
C, the input capacitor value may need to be larger.
traces.
capacitors
IND
Low
)
ESR
IND
called
) x (ESR of C
types
“high-frequency”,
capacitors
OUT
)
5-7
are
Inductor Selection
The TS2576 can be used for either continuous or
discontinuous modes of operation. Each mode has
distinctively different operating characteristics, which can
affect the regulator performance and requirements.
With relatively heavy load currents, the circuit operates
in the continuous mode (inductor current always flowing).
But under light
Load conditions, the circuit will be force to the
discontinuous mode (inductor current falls to zero for a
period of time). For light loads (less than approximately
300mA) it may be desirable to operate the regulator in
the discontinuous mode, primarily because of the lower
inductor values required for the discontinuous mode.
Indictors are available in different styles such as pot
core, toroid, E-frame, bobbin core, et., as well as
different core materials such as ferrites and powdered
iron. The least expensive, the bobbin core type, consists
of wire wrapped on a ferrite rod core. This type of
construction makes for an inexpensive inductor, but
since the magnetic flux is not completely contained
within the core, it generates more electromagnetic
interference (EMI). This EMI can cause problems in
sensitive circuits, or can give incorrect scope readings
because of induced voltage in the scope probe. An
inductor should not be operated beyond its maximum
rated current because it may saturate. When an inductor
begins to saturate, the inductance decreases rapidly and
the inductor begins to look mainly resistive (the DC
resistance of the winding). This will cause the switch
current to rise very rapidly. Different inductor types have
different saturation characteristics, and this should be
well considered when selecting as inductor.
Feedback Connection
For fixed output voltage version, the FB (feedback) pin
must be connected to V
is important to place the output voltage ratio resistors
near TS2576 as possible in order to minimize the noise
introduction.
Enable Input
It is required that the ENABLE must not be left open. For
normal operation, connect this pin to a ”LOW” voltage
(typically, below 1.6V). On the other hand, for standby
mode, connect this pin with a “HIGH” voltage. This pin
can be safely pulled up to +
with it.
OUT
2003/12 rev. A
. For the adjustable version, it
VIN
without a resistor in series