AAT3110IJS-4.5-T1 AAT [Advanced Analog Technology, Inc.], AAT3110IJS-4.5-T1 Datasheet - Page 15

• Manufacturer Part Number: AAT3110IJS-4.5-T1
• Manufacturer: AAT [Advanced Analog Technology, Inc.]

the C
itor can be increased to 22µF or more. Larger val-
ues for the C
nature have lower ESR and can improve both high
and low frequency components of the charge pump
output ripple response.
capacitor is used for C
ripple elements, a small 1µF low ESR ceramic
capacitor should be added in parallel to the tantalum
capacitor (see Figure 1). The reason for this is tan-
talum capacitors typically have higher ESR than
equivalent value ceramic capacitors and are less
able to reduce high frequency components of the
output ripple. The only disadvantage to using large
values for the C
turn-on time and inrush current may be increased.
If additional ripple reduction is desired, an R/C filter
can be added to the charge pump output in addi-
tion to the C
filter will reduce output ripple by primarily attenuat-
ing high frequency components of the output ripple
3110.2005.11.1.4
OUT
V
(5V)
V
(5V)
OUT
OUT
capacitor. The nominal 10µF C
OUT
OUT
OUT
C
C
capacitor (22µF and greater) will by
33 F
1 F
capacitor (see Figure 2). An R/C
FILTER
OUT2
capacitor is the AAT3110 device
OUT
Figure 2: Application With Output Ripple Reduction Filter.
If a higher value tantalum
ON/OFF
ON/OFF
to reduce low frequency
R
1.5
Figure 1: Application Using Tantalum Capacitor.
FILTER
22 F
C
10 F
C
OUT1
OUT
+
OUT
capac-
VOUT
GND
SHDN
VOUT
GND
SHDN
AAT3110-5
AAT3110-5
MicroPower™ Regulated Charge Pump
VIN
VIN
C+
C+
C-
C-
waveform. The low frequency break point for the
R/C filter will significantly depend on the capacitor
value selected.
Layout Considerations
High charge pump switching frequencies and large
peak transient currents mandate careful printed cir-
cuit board layout. As a general rule for charge
pump boost converters, all external capacitors
should be located as closely as possible to the
device package with minimum length trace con-
nections. Maximize the ground plane around the
AAT3110 charge pump and make sure all external
capacitors are connected to the immediate ground
plane. A local component side ground plane is rec-
ommended. If this is not possible due to layout
design limitations, assure good ground connec-
tions by the use of large or multiple PCB vias.
Refer to the AAT3110 evaluation board for an exam-
ple of good charge pump layout design (Figures 3
through 5).
C
1 F
C
1 F
FLY
FLY
+
10 F
10 F
C
C
IN
IN
V
(2.7V to 5V)
(2.7V to 5V)
V
IN
IN
AAT3110
15