FAN2514/FAN2515 PRODUCT SPECIFICATION
REV. 1.0.2 9/24/01
3
Depending on the model selected, a number of control and
status functions are av ailable to enhance the operation of the
LDO regulator . An Enable pin, av ailable on all devices,
allows the user to shut down the re gulator output to conserv e
power, reducing supply current to less than 1µA. The
adjustable-voltage versions of the de vice utilize pin 4 to
connect to an external voltage divider which feeds back to
the regulator error amplifier , thereby setting the voltage as
desired. Two other functions are a v ailable at pin 4 in the
fixed-v oltage versions: in noise-sensitive applications, an
external Bypass capacitor connection is provided that allows
the user to achiev e optimal noise performance at the output,
while the Error output functions as a diagnostic flag to
indicate that the output voltage has dropped more than 5%
below the nominal fixed voltage.
Applications Information
External Capacitors – Selection
The F AN2514/15 allows the user to utilize a wide v ariety of
capacitors compared to other LDO products. An innov ati v e
design approach offers significantly reduced sensitivity to
ESR (Effective Series Resistance), which degrades re gulator
loop stability in older designs. While the improv ements fea-
tured in the FAN2514/15 family greatly simplify the design
task, capacitor quality still must be considered if the designer
is to achie v e optimal circuit performance. In general,
ceramic capacitors offer superior ESR performance, at a
lower cost and a smaller case size than tantalums. Those with
X7R or Y5Vdielectric offer the best temperature coefficient
characteristics. The combination of tolerance and variation
ov er temperature in some capacitor types can result in signif-
icant v ariations, resulting in unstable performance ov er rated
conditions.
Input Capacitor
An input capacitor of 2.2µF (nominal v alue) or greater ,
connected between the Input pin and Ground, located in
close proximity to the device, will improve transient
response and noise rejection. Higher values will of fer supe-
rior input ripple rejection and transient response. An input
capacitor is recommended when the input source, either a
battery or a regulated AC voltage, is located far from the
device. Any good quality ceramic, tantalum, or metal film
capacitor will gi v e acceptable performance, howev er tanta-
lum capacitors with a surge current rating appropriate to the
application must be selected to avoid catastrophic failure.
Output Capacitor
An output capacitor is required to maintain regulator loop
stability. Unlike many other LDO regulators, the
FAN2514/15 family of products are nearly insensitve to
output capacitor ESR. Stable operation will be achieved with
a wide variety of capacitors with ESR v alues ranging from
10m
Ω
to 10
Ω
or more. Tantalum or aluminum electrolytic,
or multilayer ceramic types can all be used. A nominal value
of at least 1µF is recommended.
Bypass Capacitor (FAN2514 Only)
In the fixed-v oltage configuration, connecting a capacitor
between the bypass pin and ground can significantly reduce
noise on the output. Values ranging from 470pF to 10nF can
be used, depending on the sensitivity to output noise in the
application.
At the high-impedance Bypass pin, care must be taken in the
circuit layout to minimize noise pickup, and capacitors must
be selected to minimize current loading (leakage). Noise
pickup from external sources can be considerable. Leakage
currents into the Bypass pin will directly affect regulator
accuracy and should be kept as low as possible; thus, high-
quality ceramic and film types are recommended for their
low leakage characteristics. Cost-sensitive applications not
concerned with noise can omit this capacitor.
Control Functions
Enable Pin
Applying a voltage of 0.8V or less at the Enable pin will
disable the output, reducing the quiescent output current to
less than 1µA, while a voltage of 1.5V or greater will enable
the device. If this shutdown function is not needed, the pin
can simply be connected to the V
IN
pin. Allowing this pin to
float will cause erratic operation.
Error Flag (FAN2515 only)
To indicate conditions such as input voltage dropout
(low V
IN
), overheating, or overloading (excessi v e output
current), the ERR pin indicates a fault condition. It is an
open-drain output which is HIGH when the voltage at V
OUT
is greater than 95% of the nominal rated output voltage and
LOW when V
OUT
is less than 95% or the rated output
voltage, as specified in the error trip level characteristics.
A logic pullup resistor of 100K
Ω
is recommended at this
output. The pin can be left disconnected if unused.
Thermal Protection
The FAN2514/15 is designed to supply high peak output cur-
rents of up to 1A for brief periods, however this output load
will cause the device temperature to increase and exceed
maximum ratings due to power dissipation. During output
ov erload conditions, when the die temperature exceeds the
shutdown limit temperature of 190°C, onboard thermal
protection will disable the output until the temperature drops
below this limit, at which point the output is then re-enabled.
During a thermal shutdown situation the user may assert the
power-down function at the Enable pin, reducing power
consumption to the minimum level I
GND
.