FAN2011EMPX Fairchild Semiconductor, FAN2011EMPX Datasheet - Page 8

• Manufacturer Part Number: FAN2011EMPX
• Description: IC CONV DC-DC 1.5A HI EFF 6MLP
• Manufacturer: Fairchild Semiconductor
• Type: Step-Down (Buck)r

Specifications of FAN2011EMPX

• Internal Switch(s): Yes
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 0.8 ~ 5.5 V
• Current - Output: 1.5A
• Frequency - Switching: 1.3MHz
• Voltage - Input: 4.5 ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 6-MLP
• Mounting Style: SMD/SMT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

FAN2011/FAN2012 Rev. 1.0.4
Applications Information
Setting the Output Voltage
The internal reference is 0.8V. The output is divided
down by a voltage divider, R1 and R2 to the FB pin. The
output voltage is:
According to this equation, and assuming desired output
voltage of 1.5096V, and given R2 = 10K , the calculated
value of R1 is 8.87K .
Inductor Selection
The inductor parameters directly related to device perfor-
mances are saturation current and DC resistance. The
FAN2011/FAN2012 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 calculated as follows:
where:
f = Switching Frequency
L = Inductor Value
Some recommended inductors are suggested in the
table below:
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
mended. The output capacitor determines the output rip-
ple and the transient response.
Table 2. Recommended Capacitors
V
Capacitor
I
OUT
L
Inductor Value
Value
= Inductor Ripple Current
10µF
=
3.3µH
3.3µH
3.3µH
V
REF
1
IN
+
I
L
and AGND pins of the device is recom-
Vendor
R
------ -
R
Murata
Yuden
=
Taiyo
1
2
TDK
V
OUT
Coiltronics
Panasonic
Vendor
Murata
1
----------------------------------------- -
–
V
GRM32ER61C106K
L
C3216X5ROJ106M
C2012X5ROJ106K
OUT
JMK212BJ106MG
JMK316BJ106KL
Part Number
f
LQS66C3R3M04
V
Part Number
ELL6PM3R3N
IN
SD-3R3-R
8
PCB Layout Recommendations
The inherently high peak currents and switching fre-
quency of power supplies require a careful PCB layout
design. Therefore, use wide traces for high-current paths
and place the input capacitor, the inductor, and the out-
put capacitor as close as possible to the integrated cir-
cuit terminals. To minimize voltage stress to the device
resulting from ever-present switching spikes, use an
input bypass capacitor with low ESR. Use of an external
Schottky diode, with its anode connected to SW node
and cathode connected to PV
ing spikes. 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. The recom-
mended PCB layout is shown below in Figure 5
Figure 5. Recommended PCB Layout
IN
, further reduces switch-
www.fairchildsemi.com
.