www.fairchildsemi.com
FAN2534/FAN2535
150 mA CMOS LDO Regulator with Fast Start, Enable
Features
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70dB Ripple rejection ( >45dB up to 1MHz)
150µsec Power On Time
150µsec Enable Time
Low noise - 50µVrms
Enable optimized for CDMA time slices
180 mV dropout voltage at 150 mA
Enable/Shutdown Control
Enable time independent of noise bypass capacitor value
SOT23-5 package
Thermal limiting
300 mA trimmed current limit
low dropout voltage, fast enable required in CDMA handset
applications, exceptional loop stability to accommodate a
wide variety of external capacitors, and a compact SOT23-5
surface-mount package. These products offer significant
improvements over older Bipolar and CMOS designs and are
pin-compatible with many popular devices.
The FAN2534 and FAN2535 devices are distinguished by
the assignment of pin 4:
FAN2534:
pin 4 – ADJ, allowing the user to adjust the
output voltage over a wide range using an external voltage
divider.
FAN2534-XX:
pin 4 – BYP, to which a bypass capacitor
may be connected for optimal noise performance. Output
voltage is fixed, as specified by the suffix XX.
FAN2535-XX:
pin 4 – ERR, a flag which indicates that the
output voltage has dropped below the specified minimum
due to a fault condition.
The standard fixed output voltages available are 2.6V, 2.85V,
and 3.0V . Custom output voltages are also available: please
contact your local Fairchild Sales Office for information.
Applications
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Cellular Phones and accessories
PDAs
Portable cameras and video recorders
Laptop, notebook and palmtop computers
Description
The FAN2534/FAN2535 family of micropower low-dropout
voltage regulators utilize CMOS technology to offer a new
level of cost-effective performance in GSM, TDMA, and
CDMA cellular handsets, laptop and notebook computers,
and other portable devices. Proprietary design technics
ensure high ripple rejection. Other features include low
noise, short circuit current limit, thermal shutdown circuit,
Block Diagrams
EN
VIN
Bandgap
Error
Amplifier
p
VOUT
ADJ
Thermal
Sense
FAN2534
GND
FAN2534-XX
Thermal
Sense
Thermal
Sense
FAN2535-XX
VIN
BYP
Bandgap
Error
Amplifier
p
VOUT
EN
VIN
Bandgap
p
VOUT
EN
ERR
Error
Amplifier
GND
GND
REV. 1.0.2 8/26/03
FAN2534/FAN2535
PRODUCT SPECIFICATION
Switching Characteristics
(Notes 4, 5)
Parameter
Conditions
Min.
Typ.
Max.
Unit
Enable Response time (Note 8)
Power "ON" Response time
Error Flag Response time
(FAN2535-XX only)
C
L
=10µF C
BP
=10nF
C
L
=10uF C
BP
=10nF
V
OUT
= 3.0V
150
150
300
500
3
µsec
µsec
msec
AC Performance Characteristics
(Notes 4, 5)
Symbol
Parameter
Conditions
Min.
Typ.
Max.
Units
∆
V
OUT
/
∆
V
IN
∆
V
OUT
/
V
OUT
e
N
Line regulation
Load regulation
Output noise
V
IN
= (V
OUT
+ 1) to 6.5V, I
L
= 10mA
I
OUT
= 0.1 to 100mA
BW: 300Hz–50KHz
C
OUT
= 10µF,
C
BYP
= 0.01µF
100 Hz,
C
OUT
= 1µF,
C
BYP
= 0.01µF
0mA<I
L
<150mA
0.05
1.0
50
0.2
2.0
% /V
%
µV
RMS
PSRR
Power Supply
Ripple Rejection
70
dB
Notes:
1. Functional operation under any of these conditions is NOT implied. Performance and reliability are guaranteed only
if Operating Conditions are not exceeded.
2. Using Mil Std. 883E, method 3015.7(Human Body Model), 400V when using JEDEC method A115-A (Machine Model).
3. For specific output voltages of the fixed oputput voltage versions please refer to the table: "Output Voltage Options and
Ordering Information" on Page 9. Custom fixed output voltages, not listed in the table, are also available.
4. Unless otherwise stated, T
A
= 25°C, V
IN
= V
OUT
+ 1V, I
OUT
= 100µA, V
EH
> 2.0 V.
5. Bold values indicate -40 <T
J
<125°C.
6. Dropout Voltage is defined as the input to output differential at which the output voltage drops to 2% below the nominal value
measured at 1V input - output differential.
7. Adjustable version, has a bandgap reference voltage of 1.0V, trimmed to +/-1% initial accuracy.
8. When using repeated cycling, F>0.5Hz.
4
REV. 1.0.2 8/26/03
PRODUCT SPECIFICATION
FAN2534/FAN2535
Functional Description
Utilizing CMOS technology, the FAN2534/FAN2535
product family is optimized for use in compact battery
powered systems, offering a unique combination of high
ripple rejection, low noise, low power consumption,
extremely low dropout voltages, high tolerance for a variety
of output capacitors, and less than 1µA "OFF" current.
In the circuit, a differential amplifier controls a series-pass
P-Channel MOSFET, and a separate error amplifier com-
pares the load voltage at the output with an onboard trimmed
low voltage bandgap reference. The series resistance of the
pass P-Channel MOSFET is approximately 1 Ohm, yielding
an unusually low dropout voltage even under high load
conditions.
Thermal shutdown and current limit circuits protect the
device under extreme conditions. When the device tempera-
ture reaches 155°C, the output is disabled, until the device
cooles down by 15°C, then re-enabled. The user can to shut
down the device using the Enable control pin at any time.
The current limit circuit is trimmed, which leads to consis-
tent power on /enable delays, and provides safe short circuit
current densities even in narrow traces of the PCB.
A carefully optimized control loop accommodates a wide
range of ESR values in the output bypass capacitor, allowing
the user to optimize space, cost, and performance require-
ments.
An Enable pin shuts down the regulator output to conserve
power, reducing supply current to less than 1µA. The output
can then be re-Enabled within 150µSec, fulfilling the fast
power-cycling needs of CDMA applications.
Depending on the device type selected, other control and
status functions are available at pin 4. The fixed-voltage
versions are available with either a noise-bypass pin or an
Error flag pin option. The error flag can be used as a diagnos-
tic function to indicate that the output voltage has dropped
more than 5% below the nominal value.
The adjustable-voltage versions utilize pin 4 to connect to an
external voltage divider which feeds back to the regulator
error amplifier, thus setting the output voltage to the desired
value.
Applications Information
External Capacitors – Selection
The FAN2534/FAN2535 allows the user to utilize a wide
variety of capacitors compared to other LDO products.
An innovative design approach offers significantly reduced
sensitivity to ESR (Equivalent Series Resistance), which
degrades regulator loop stability in older designs. While the
improvements featured in the FAN2534/FAN2535 family
greatly simplify the design task, capacitor quality still must
be considered if the designer is to achieve optimal circuit
performance. In general, ceramic capacitors offer superior
ESR performance, and a smaller case size than tantalums.
Input Capacitor
An input capacitor of 2.2µF (nominal value) or greater,
connected between the Input pin and Ground, placed in close
proximity to the device, will improve transient response and
ripple rejection. Higher values will further improve 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 give acceptable performance, however in extreme cases
capacitor surge current ratings may have to be considered.
Output Capacitor
An output capacitor is required to maintain regulator loop
stability. Stable operation will be achieved with a wide
variety of capacitors with ESR values ranging from 0mΩ
up to 400mΩ. Multilayer ceramic, tantalum or aluminum
electrolytic capacitors may be used. A nominal value of at
least 1µF is recommended. Note that the choice of output
capacitor effects load transient response, ripple rejection,
and it has a slight effect on noise performance as well.
Bypass Capacitor (FAN2534-XX Only)
In the fixed-voltage configuration, connecting a capacitor
between the bypass pin and ground can significantly reduce
output noise. Values ranging from 0pF to 47nF 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
PCB 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.
REV. 1.0.2 8/26/03
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