EUP7961
Application Note
Input Capacitor
voltage is calculated using:
An input capacitance of 1µF is required between the
EUP7961 input pin and ground (the amount of the
capacitance may be increased without limit).This
capacitor must be located very close to the input pin and
returned to a clean analog ground. Any good quality
ceramic, tantalum, or film capacitor can be used at the
input. If a tantalum capacitor is used at the input, it must
be guaranteed by the manufacturer to have asurge current
rating sufficient for the application. There are no
requirements for the ESR on the input capacitor, but
tolerance and temperature coefficient must be considered
when selecting the capacitor to ensure the capacitance
will be 1µF over the entire operating temperature range.
R
R
1
V = V ×(1+
)
O
ref
2
Where:
Vref= 0.8V typ. (the internal reference voltage)
Utilize the following equation for adjusting the output to
a particular voltage:
V
O
P = R
−1
I
2
0.8V
Choose R2=50k to optimize accuracy, power supply
rejection, noise and power consumption.
Output Capacitor
The EUP7961 is designed specifically to work with small
ceramic output capacitors.
A
ceramic capacitor
(temperature characteristics X7R, X5R, Z5U, or Y5V) in
4.7µF to 22µF range with 5mΩ to 200mΩ ESR range is
suitable in the EUP7961 application circuit.
The output capacitor must meet the requirement for
minimum 4.7µF over the entire operating range and also
have an ESR (Equivalent Series Resistance) value which
is within a stable range (5mΩ to 200mΩ)
No-Load Stability
The EUP7961 will remain stable and in regulation with
no external load. This is specially important in CMOS
RAM keep-alive applications.
On/Off Input Operation
Power Dissipation
The EUP7961 is turned off by pulling the VEN pin low,
and turned on by pulling it high. If this feature is not used,
the VEN pin should be tied to VIN to keep the regulator
output on at all time. To assure proper operation, the
signal source used to drive the VEN input must swing
above and below the specified turn-on/off voltage
thresholds listed in the Electrical Characteristics section
under VIL and VIH.
EUP7961 can deliver a continuous current of 2A over the
full operating temperature range. 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:
Flag Operation
ERROR
The EUP7961 produces a logic low signal at the
P
=
V
− V
I
+
V
I
D
IN
OUT OUT
IN GND
Flag pin when the output drops out of
ERROR
Where IGND is the operating ground current of the device
(specified under Electrical Characteristics).
regulation due to low input voltage, current limiting, or
thermal limiting. This flag has a built in hysteresis.
The maximum allowable temperature rise (TRmax
depends on the maximum ambient temperature (TAmax
)
)
The
ERROR
is an open drain output. Hence, the
ERROR
pin should be pulled high through a pull up
resistor. The
of the application, and the maximum allowable junction
temperature (TJmax):
pin must be connected to ground
ERROR
if this function is not used. In shutdown, the
pin is Hi-Z state to save input power.
ERROR
TRmax= TJmax-TAmax
The maximum allowable value for junction to ambient
Thermal Resistance, θJA , can be calculated using the
formula:
Adjustable Operation
The adjustable version of the EUP7961 has an output
voltage range of 0.8V to 4.5V. The output voltage of the
EUP7961 adjustable regulator is programmed using an
external resistor divider as shown in Figure3. The output
θJA =TRmax/PD
DS7961 Ver 1.4 Jan. 2009
9
EUTECH [ EUTECH MICROELECTRONICS INC ]
