Designed for use in battery-powered applications, the FAN2001/
IN
FAN2002 is a high-efficiency, low-noise synchronous PWM current mode and Pulse Skip (Power Save) mode DC-DC converter. It can provide up to 1A of output current over a wide input
range from 2.5V to 5.5V. The output voltage can be externally
adjusted over a wide range of 0.8V to 5.5V by means of an
external voltage divider.
At moderate and light loads, pulse skipping modulation is used.
Dynamic voltage positioning is applied, and the output voltage is
shifted 0.8% above nominal value for increased headroom during load transients. At higher loads the system automatically
switches over to current mode PWM control, operating at 1.3
MHz. A current mode control loop with fast transient response
ensures excellent line and load regulation. To achieve high efficiency and ensure long battery life, the quiescent current is
reduced to 25µA in Power Save mode, and the supply current
drops below 1µA in shut-down mode. The FAN2001/FAN2002 is
available in a 3x3mm 6-lead MLP package.
1. Stresses above those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress rating only and functional
operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure
to absolute maximum rating conditions for extended periods may affect device reliability. Absolute maximum ratings apply individually only, not in
combination. Unless otherwise specified, all other voltages are referenced to AGND.
2. Junction to ambient thermal resistance, θ
via used, diameter of via used, available copper surface, and attached heat sink characteristics.
3. Using Mil Std. 883E, method 3015.7(Human Body Model) and EIA/JESD22C101-A (Charge Device Model).
4. Refer to the applications section for further details.
, is a strong function of PCB material, board thickness, thickness and number of copper planes, number of
JA
FAN2001/FAN2002 Rev. 1.0.2
3
www.fairchildsemi.com
Page 4
≤
≤
Electrical Characteristics
V
= V
IN
Unless otherwise noted. Typical values are at T
SymbolParameterConditionsMin.Typ.Max.Units
V
IN
I
Q
V
ENH
V
ENL
I
EN
R
DS-ON
I
LIM
I
lkg_(N)
I
lkg_(P)
VrefReference Voltage0.8V
Notes:
5. Refer to the application section for further details.
6. For output voltages ≤ 1.2V a 40 µ F output capacitor value is required to achieve a maximum output accuracy of 3% while operating in power save
The FAN2001/FAN2002 is a step-down converter operating in a
current-mode PFM/PWM architecture with a typical switching
frequency of 1.3MHz. At moderate to heavy loads, the converter
operates in pulse-width-modulation (PWM) mode. At light loads
the converter enters a power-save mode (PFM pulse skipping)
to keep the efficiency high.
PWM Mode
In PWM mode, the device operates at a fixed frequency of
1.3MHz. At the beginning of each clock cycle, the P-channel
transistor is turned on. The inductor current ramps up and is
monitored via an internal circuit. The P-channel switch is turned
off when the sensed current causes the PWM comparator to trip
when the output voltage is in regulation or when the inductor
current reaches the current limit (set internally to typically
1500mA). After a minimum dead time the N-channel transistor
is turned on and the inductor current ramps down. As the clock
cycle is completed, the N-channel switch is turned off and the
next clock cycle starts.
PFM (Power Save) Mode
As the load current decreases and the inductor current reaches
negative value, the converter enters pulse-frequency-modulation (PFM) mode. The transition point for the PFM mode is given
by the equation:
1V
I
OUTVOUT
------------------------------------------
×=
The typical output current when the device enters PFM mode is
150mA for input voltage of 3.6V and output voltage of 1.2V. In
OUTVIN
2Lf××
⁄()–
NEG.
NEG.
LIMIT
COMP
LIMIT
SENSE
GND
PFM mode the device operates with a variable frequency and
constant peak current, thus reducing the quiescent current to
minimum. Consequently, the high efficiency is maintained at
light loads. As soon as the output voltage falls below a threshold, set at 0.8% above the nominal value, the P-channel transistor is turned on and the inductor current ramps up. The Pchannel switch turns off and the N-channel turns on as the peak
inductor current is reached (typical 450mA).
The N-channel transistor is turned off before the inductor current becomes negative. At this time the P-channel is switched
on again starting the next pulse. The converter continues these
pulses until the high threshold (typical 1.6% above nominal
value) is reached. A higher output voltage in PFM mode gives
additional headroom for the voltage drop during a load transient
from light to full load. The voltage overshoot during this load
transient is also minimized due to active regulation during turn
on of the N-channel rectifier switch. The device stays in sleep
mode until the output voltage falls below the low threshold. The
FAN2001/FAN2002 enters the PWM mode as soon as the output voltage can no longer be regulated in PFM with constant
peak current.
100% Duty Cycle Operation
As the input voltage approaches the output voltage and the duty
cycle exceeds the typical 95%, the converter turns the P-channel transistor continuously on. In this mode the output voltage is
equal to the input voltage minus the voltage drop across the Pchannel transistor:
The reference and the circuit remain reset until the VIN crosses
its UVLO threshold.
The FAN2001/FAN2002 has an internal soft-start circuit that
limits the in-rush current during start-up. This prevents possible
voltage drops of the input voltage and eliminates the output voltage overshoot. The soft-start is implemented as a digital circuit
increasing the switch current in four steps to the P-channel current limit (1500mA). Typical start-up time for a 20µF output
capacitor and a load current of 1000mA is 800µs.
Short Circuit Protection
The switch peak current is limited cycle-by-cycle to a typical
value of 1500mA. In the event of an output voltage short circuit,
the device operates with a frequency of 400kHz and minimum
duty cycle, therefore the average input current is typically
200mA.
Thermal Shutdown
When the die temperature exceeds 150°C, a reset occurs and
will remain in effect until the die cools to 130°C, at that time the
circuit will be allowed to restart.
Applications Information
Setting the Output Voltage
The internal reference is 0.8V (Typical). The output voltage is
divided by a resistor divider, R1 and R2 to the FB pin. The output voltage is given by:
R
1
=
SW
6
5
NC
FB
4
1
-------+
R
2
3.3µH
C
50KΩ
R1
100KΩ
R2
V
OUT
f
1.2V (1A)
C
OUT
2 x 10µF
V
OUTVREF
Where R
+ R2 < 800KΩ.
1
According to this equation, and assuming desired output voltage of 1.5096V, and given R2 = 10KΩ, the calculated value of
R1 is 8.87KΩ. If quiescent current is a key design parameter a
higher value feedback resistor can be used (e.g. R2 = 100KΩ)
and a small bypass capacitor of 10pF is required in parallel with
the upper resistor as shown in Figure 4.
V
IN
10µF
C
IN
PGND
1
P1
2
(AGND)
EN
3
This is calculated as follows:
∆ILV
1V
×=
-----------------------------------------
OUT
⁄()–
OUTVIN
Lf×
where:
∆IL = Inductor Ripple Current
f = Switching Frequency
L = Inductor Value
Some recommended inductors are suggested in the table
below:
Inductor ValueVendorPart Number
3.3µHPanasonicELL6PM3R3N
3.3µHMurataLQS66C3R3M04
Table 1: Recommended Inductors
Capacitors Selection
For best performances, a low ESR input capacitor is required. A
ceramic capacitor of at least 10µF, placed as close to the V
and AGND pins of the device is recommended. The output
capacitor determines the output ripple and the transient
response.
Capacitor
VendorPart Number
Value
10µFTaiyo YudenJMK212BJ106MG
JMK316BJ106KL
TDKC2012X5ROJ106K
C3216X5ROJ106M
MurataGRM32ER61C106K
Table 2: Recommended Capacitors
PCB Layout Recommendations
The recommended PCB layout is shown in Figures 5 and 6. The
inherently high peak currents and switching frequency of power
supplies require a careful PCB layout design.
IN
Figure 4. Setting the Output Voltage
Inductor Selection
The inductor parameters directly related to the device’s performances are saturation current and dc resistance. The FAN2001/
FAN2002 operates with a typical inductor value of 3.3µH. The
lower the dc resistance, the higher the efficiency. For saturation
current, the inductor should be rated higher than the maximum
load current plus half of the inductor ripple current.
Therefore, use wide traces for high current paths and place the
input capacitor, the inductor, and the output capacitor as close
as possible to the integrated circuit terminals. In order to minimize voltage stress to the device resulting from ever present
switching spikes, use an input bypass capacitor with low ESR.
Note that the peak amplitude of the switching spikes depends
upon the load current; the higher the load current, the higher the
switching spikes. The resistor divider that sets the output voltage should be routed away from the inductor to avoid RF coupling. The ground plane at the bottom side of the PCB acts as
an electromagnetic shield to reduce EMI.
For more board layout recommendations download the application note “PCB Grounding System and FAN2001/FAN2011 High
Performance DC-DC Converters” (AN-42036).
The following are registered and unregistered trademarks Fairchild Semiconductor owns or is authorized to use and is
not intended to be an exhaustive list of all such trademarks.
ACEx™
ActiveArray™
Bottomless™
FPS™
CoolFET™
CROSSVOL T™
DOME™
EcoSPARK™
2
CMOS™
E
EnSigna™
FACT™
FACT Quiet Series™
Across the board. Around the world.™
The Power Franchise
Programmable Active Droop™
DISCLAIMER
FAIRCHILD SEMICONDUCTOR RESERVES THE RIGHT TO MAKE CHANGES WITHOUT FURTHER NOTICE TO ANY
PRODUCTS HEREIN TO IMPROVE RELIABILITY, FUNCTION OR DESIGN. FAIRCHILD DOES NOT ASSUME ANY LIABILITY
ARISING OUT OF THE APPLICATION OR USE OF ANY PRODUCT OR CIRCUIT DESCRIBED HEREIN; NEITHER DOES IT
CONVEY ANY LICENSE UNDER ITS PATENT RIGHTS, NOR THE RIGHTS OF OTHERS.
FAIRCHILD’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT
DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF FAIRCHILD SEMICONDUCTOR CORPORATION.
As used herein:
1. Life support devices or systems are devices or
systems which, (a) are intended for surgical implant into
the body, or (b) support or sustain life, or (c) whose
failure to perform when properly used in accordance
with instructions for use provided in the labeling, can be
reasonably expected to result in significant injury to the
user.
PRODUCT STATUS DEFINITIONS
Definition of Terms
Datasheet IdentificationProduct StatusDefinition
Advance Information
Preliminary
No Identification Needed
Formative or
In Design
First Production
Full Production
2. A critical component is any component of a life
support device or system whose failure to perform can
be reasonably expected to cause the failure of the life
support device or system, or to affect its safety or
effectiveness.
This datasheet contains the design specifications for
product development. Specifications may change in
any manner without notice.
This datasheet contains preliminary data, and
supplementary data will be published at a later date.
Fairchild Semiconductor reserves the right to make
changes at any time without notice in order to improve
design.
This datasheet contains final specifications. Fairchild
Semiconductor reserves the right to make changes at
any time without notice in order to improve design.
Obsolete
FAN2001/FAN2002 Rev. 1.0.2
Not In Production
This datasheet contains specifications on a product
that has been discontinued by Fairchild semiconductor.
The datasheet is printed for reference information only.
Rev. I15
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