AAT1230/1230-1
18V 100mA Step-Up Converter
D1
L1
2.2µH
R4
10K
VIN
VOUT
Schottky
JP1
U1
VP
EN/SET FB1
1
2
3
4
5
6
12
11
10
9
3
2
1
LIN
R1
78.7k
SEL
VIN
N/C
SW
FB2
GND
PGND
SW
8
Enable
JP2
C2
2.2µF
7
C1
2.2µF
R2
562
3
2
1
R3
4.99k
Select
U1 AAT1230/1230-1 TSOPJW12
C1 10V 0603 2.2µF
C2 25V 0805 2.2µF
D1 30V 0.5A MBR0530T1 SOD-123
L1 2.2µH SD3814-2R2
R1 78.7k 0603
R2 562 0603
R3 4.99k 0603
Figure 1: AAT1230/1230-1 Demo Board Schematic.
transferred from the input battery and boost induc-
tor to the output load through the output diode.
Duty cycle is defined as the ON time divided by the
total switching interval.
Application Information
Selecting the Output Diode
To ensure minimum forward voltage drop and no
recovery, high voltage Schottky diodes are consid-
ered the best choice for the AAT1230/1230-1 boost
converter. The AAT1230/1230-1 output diode is
sized to maintain acceptable efficiency and reason-
able operating junction temperature under full load
operating conditions. Forward voltage (VF) and
package thermal resistance (θJA) are the dominant
factors to consider in selecting a diode. The diode's
published current rating may not reflect actual oper-
ating conditions and should be used only as a com-
parative measure between similarly rated devices.
20V rated Schottky diodes are recommended for
outputs less than 15V, while 30V rated Schottky
diodes are recommended for outputs greater than
15V.
TON
D =
TON + TOFF
= TON ⋅ FS
The maximum duty cycle can be estimated from
the relationship for a continuous mode boost con-
verter. Maximum duty cycle (DMAX) is the duty
cycle at minimum input voltage (VIN(MIN)).
VOUT - VIN(MIN)
VOUT
DMAX
=
The switching period is divided between ON and
OFF time intervals.
The average diode current during the OFF time can
be estimated.
1
= TON + TOFF
FS
IOUT
1 - DMAX
IAVG(OFF)
=
During the ON time, the N-channel power MOS-
FET is conducting and storing energy in the boost
inductor. During the OFF time, the N-channel
power MOSFET is not conducting. Stored energy is
The following curves show the VF characteristics
for different Schottky diodes (100°C case). The VF
of the Schottky diode can be estimated from the
average current during the off time.
10
1230.2006.10.1.4
ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
