EUP7966
Application Note
External Capacitors
The maximum allowable value for junction to ambient
Thermal Resistance, θJA, can be calculated using the
formula:
To assure regulator stability, input and output capacitors
are required as shown in the Typical Application Circuit.
Output Capacitor
The EUP7966 is designed specifically to work with very
small ceramic output capacitors. A ceramic capacitor
(temperature characteristics X7R, X5R, Z5U, or Y5V) in
4.7 to 22µF range with 5mΩ to 200mΩ ESR range is
suitable in the EUP7966 application circuit.
θJA=TRmax/PD
Heatsinking for the SOP-8 (FD) package is
accomplished by allowing heat to flow through the
ground slug on the bottom of the package into the
copper on the PC board. The heat slug must be
soldered down to a copper plane to get good heat
transfer. It can also be connected through vias to
internal copper planes .Since the heat slug is at ground
potential, traces must not be routed under it which are
not at ground potential. Under all possible conditions,
the junction temperature must be within the range
specified under operating conditions.
The output capacitor must meet the requirement for
minimum amount of capacitance and also have an ESR
(Equivalent Series Resistance) value which is within a
stable range (5mΩ to 200mΩ)
Input Capacitor
The input capacitor must be at least 10 µF ceramic, but
can be increased without limit. It’s purpose is to provide a
low source impedance for the regulator input.
Bias Capacitor
The 1µF capacitor on the bias line can be any good
quality capacitor (ceramic is recommended).
Bias Voltage
The bias voltage is an external voltage rail required to
get gate drive for the N-FET pass transistor. Bias
voltage must be in the range of 4.5 – 5.5V to assure
proper operation of the part.
Shutdown Operation
Pulling down the VEN pin will turn-off the regulator.
VEN pin must be actively terminated through a pull-up
resistor (10 kΩ to 100 kΩ) for a proper operation. If this
pin is driven from a source that actively pulls high and
low (such as a CMOS rail to rail comparator) , the pull-up
resistor is not required. This pin must be tied to VIN if
not used.
Power Dissipation /Heatsinking
A heatsink may be required depending on the
maximum power dissipation and maximum ambient
temperature of the application. Under all possible
conditions, the junction temperature must be within the
range specified under operating conditions. The total
power dissipation of the device is given by:
PD=(VIN-VOUT)IOUT+(VIN)IGND
where IGND is the operating ground current of the
device. The maximum allowable temperature rise
on the maximum ambient temper
) depends
(TRmax
-ature (TAmax) of the appli
cation, and the maximum
allowable junction temperature (TJmax):
TRmax=TJmax-TAmax
DS7966 Ver1.0 Aug. 2006
10
EUTECH [ EUTECH MICROELECTRONICS INC ]
