AAT3104IJQ-1-T1 ANALOGICTECH [Advanced Analogic Technologies], AAT3104IJQ-1-T1 Datasheet - Page 12

• Manufacturer Part Number: AAT3104IJQ-1-T1
• Description: Low Cost 1x/2x 4 Channel Charge Pump WLED Driver
• Manufacturer: ANALOGICTECH [Advanced Analogic Technologies]

Equivalent Series Resistance
ESR is an important characteristic to consider when
selecting a capacitor. ESR is a resistance internal to a
capacitor that is caused by the leads, internal connec-
tions, size or area, material composition, and ambient
temperature. Capacitor ESR is typically measured in mil-
liohms for ceramic capacitors and can range to more
than several ohms for tantalum or aluminum electrolytic
capacitors.
Ceramic Capacitor Materials
Ceramic capacitors less than 0.1μF are typically made
from NPO or C0G materials. NPO and C0G materials gen-
erally have tight tolerance and are very stable over tem-
perature. Larger capacitor values are usually composed
of X7R, X5R, Z5U, or Y5V dielectric materials. Large
ceramic capacitors (i.e., larger than 2.2μF) are often
available in low cost Y5V and Z5U dielectrics, but capac-
12
ChargePump
TM
Input Voltage
> V
Input Voltage
2.7V to 5.5V
F
+ V
Interface
S
EN/SET
Interface
S
EN/SET
2
Cwire
Figure 4: Higher Current, Single LED Application.
2
DROP
Cwire
Figure 5: Lower Cost 1X Mode Application.
1µF
1µF
C
C
IN
IN
1µF
C
Low Cost 1x/2x 4 Channel Charge Pump WLED Driver
P
w w w . a n a l o g i c t e c h . c o m
IN
C+
EN/SET
C-
IN
C+
EN/SET
C-
AAT3104
GND
AAT3104
GND
OUT
itors larger than 1μF are not typically required for
AAT3104 applications. Capacitor area is another con-
tributor to ESR. Capacitors that are physically large will
have a lower ESR when compared to an equivalent
material smaller capacitor. These larger devices can
improve circuit transient response when compared to an
equal value capacitor in a smaller package size.
Evaluation Board Layout
When designing a PCB for the AAT3104, the key require-
ments are:
1. Place two flying capacitors C1 and C2 as close to the
2. Place input and output decoupling capacitors as
D1
D2
D3
D4
OUT
D1
D2
D3
D4
chip as possible; otherwise 2x mode performance
will be compromised.
close to the chip as possible to reduce switching
noise and output ripple.
C
1µF
OUT
C
1µF
OUT
PRODUCT DATASHEET
AAT3104178
3104.2008.09.1.0