1-Cell to 3-Cell Boost with True Load Disconnect, 3.3V, 5V, or Adjustable Output
Layout and Grounding Considerations
External Component Selection
High frequency switching and large peak currents means
PCB design for DC-DC converters requires careful consid-
eration. A general rule is to place the DC-DC converter cir-
cuitry well away from any sensitive RF or analog compo-
nents. The layout of the DC-DC converters and its exter-
nal components are also based on some simple rules to
minimise EMI and output voltage ripple.
Inductors
The ILC6382 is designed to work with a 15µH inductor in
most applications. There are several vendors who supply
standard surface mount inductors to this value. Suggested
suppliers are shown in table 1. Higher values of inductance
will improve efficiency, but will reduce peak inductor current
and consequently ripple and noise, but will also limit output
current.
Layout
1. Place all power components, ILC6382, inductor,
input capacitor and output capacitor as close together
as possible.
2. Keep the output capacitor as close to the ILC6382 as
possible with very short traces to the VOUT and GND
pins. Typically it should be within 0.25 inches or 6mm.
3. Keep the traces for the power components wide, typi-
cally >50mil or 1.25mm.
Vendor
Coilcraft
Part No
DO3308P-153
D03316P-153
D01608C-153
LQH4N150K
LQH3C150K
CDR74B-150MC
CD43-150
Contact
(847) 639 6400
muRata
Sumida
(814) 237 1431
(847) 956 0666
CD54-150
NLC453232T-150K
4. Place the external networks for LBI and VFB close to
the ILC6382, but away from the power components as far
as possible.
TDK
(847) 390 4373
Capacitors
Grounding
1. Use a star grounding system with separate traces for
the power ground and the low power signals such as
LBI/SD and VFB. The star should radiate from where the
power supply enters the PCB.
2. On multilayer boards use component side copper for
grounding around the ILC6382 and connect back to a
quiet ground plane using vias.
Input Capacitor
The input capacitor is necessary to minimize the peak cur-
rent drawn from the battery. Typically a 10µF tantalum
capacitor is recommended. Low equivalent series resist-
ance ( ESR ) capacitors will help to minimize battery voltage
ripple.
Output Capacitor
Low ESR capacitors should be used at the output of the
ILC6382 to minimize output ripple. The high switching
speeds and fast changes in the output capacitor current,
mean that the equivalent series impedance of the capacitor
can contribute greatly to the output ripple. In order to mini-
mize these effects choose an output capacitor with less
than 10nH of equivalent series inductance (ESL) and less
than 100mΩ of equivalent series resistance (ESR).
Typically these characteristics are met with ceramic capac-
itors, but may also be met with certain types of tantalum
capacitors. Suitable vendors are shown in table 2.
ILC6382
CIN
10µF
L1
VOUT
1
2
3
4
8
7
6
5
LX
VOUT
GND
COUT
10µF
+
15µH
VIN
R1
R2
R3
VIN
LBI/SD
SYNC
LBO
VFB
ON/OFF
R4
Local "Quiet" Ground
Power Ground
Recommended application circuit schematic for ILC6382CIR-ADJ
Description
T495 series tantalum
595D series tantalum
TAJ, TPS series tantalum
X7R Ceramic
Vendor
Kemet
Sprague
AVX
TDK
AVX
Contact
(864) 963 6300
(603) 224 1961
(803) 946 0690
(847) 390 4373
(803) 946 0690
Impala Linear Corporation
ILC6382 1.5
www.impalalinear.com
Oct 1999
(408) 574-3939
9
IMPALA [ Impala Linear Corporation ]
