CM2593/P
2A Step Down VOLTAGE REGULATOR
FUNCTIONAL DESCRIPTION
Pin Functions
+V
IN
This is the positive input supply for the IC switching
regulator. A suitable input bypass capacitor must be
present at this pin to minimize voltage transients and to
supply the switching currents needed by the regulator.
Out
Internal switch and power output. The voltage at this pin
switches between (+V
IN
– V
SAT
) and approximately –
0.5V, with a duty cycle of approximately V
OUT
/ V
IN
. The
PC board copper area connected to this pin should be
kept a minimum in order to reduce the coupling
sensitivity to the circuitry
Ground
Circuit ground.
Feedback
Complete the feedback loop by sensing the regulated
output voltage
ON
/OFF
Allows the switching regulator circuit to be shutdown
Thermal Considerations
The SOP-8 package needs a heat sink under most
conditions . The size of the heat-sink depends on the
input voltage, the output voltage, the load current and the
ambient
temperature.
The
CM2593/P
junction
temperature rises above ambient temperature for a 2A
load and different input and output voltages. The data
for these curves was taken with the CM2593/P (SOP-8
package) operating as a buck switching regulator in an
ambient temperature of 25
o
C (still air). These temperature
increments are all approximate and are affected by many
factors. Some of these factors include board size,
shape ,thickness ,position ,location, and even board
temperature. Other factors are trace width, total printed
circuit copper area, copper thickness , single or
double-sided, multi-layer board and amount of solder on
the board. Higher ambient temperatures require more
heat sinking.
For the best thermal performance ,wide copper traces
and generous amounts of printed circuit board copper
should be used in the board layout. (One exception is the
out(switch) pin, which should not have large areas of
copper.) Large areas of copper provide the best transfer
of heat(lower thermal resistance) to the surrounding air,
and moving air lowers the thermal resistance even
further.
The effectiveness of the PC board to dissipate heat also
depends on the size, quantity and spacing of other
components on the board , as well as whether the
surrounding air is still or moving. Furthermore, some of
these components such as the catch diode will add heat
to the PC board and heat can vary as the input voltage
changes. For the inductor, depending on the physical
size, type of core material and the DC resistance, it could
either act as a heat sink taking heat away from the board,
or it could add heat to the board.
using logic level signals thus dropping the total input
supply current to approximately 100uA. Pulling this pin
below a threshold voltage of approximately 1.3V turns
the regulator on, and pulling this pin above 1.3V (up to a
maximum of 25V) shuts the regulator down. If this
shutdown feature is not needed, the
ON
/OFF pin can
be wired to the ground pin or it can be left open, in either
case the regulator will be in the ON condition.
2007/01/25
Rev. 1.4
Champion Microelectronic Corporation
Page 6
CHAMP [ CHAMPION MICROELECTRONIC CORP. ]
