PRODUCT DATASHEET
AAT2784
SystemPowerTM
3-Channel Step-Down DC/DC Converter
Channel 3 Output Capacitor
3 · ΔILOAD1
3 · 1.5A
COUT3
=
=
= 12.5µF; use 22µF
VDROOP · FS
0.2V · 1.8MHz
VOUT · (VIN(MAX) - VOUT
)
1
1.2V · (4.2V - 1.2V)
1
·
= 92mA
IRMS(MAX)
=
·
=
1.5µH · 1.8MHz · 4.2V
L · FS · VIN(MAX)
2· 3
2· 3
PESR = ESR · IRMS2 = 5mΩ · 92mA2 = 0.042mW
Channels 1 and 2 Output Capacitors
3 · ΔILOAD1
3 · 0.3A
COUT1 = COUT2
=
=
= 2.5µF; use 4.7µF
VDROOP · FS
0.2V · 1.8MHz
VOUT1 · (VIN(MAX) - VOUT1
L · FS · VIN(MAX)
)
1
3.3V · (4.2V - 3.3V)
4.7µH · 1.8MHz · 4.2V
1
·
= 24mA
IRMS(MAX)
=
·
=
2· 3
2· 3
PESR = ESR · IRMS2 = 5mΩ · 24mA2 = 3µW
Channel 3 Input Capacitor
Input Ripple VPP = 33mV
1
1
- 5mΩ · 4 · 1.8MHz
CIN3
=
=
= 9.3µF; use 10µF
VPP
IO3
33mV
1.5A
- ESR · 4 · FS
IO
IRMS(MAX)
=
= 0.75A
2
PESR = ESR · IRMS2 = 5mΩ · (0.75A)2 = 3mW
Channels 1 and 2 Input Capacitors
Input Ripple VPP = 15mV
1
1
CIN1 = CIN2
=
=
= 6.9µF; use 10µF
VPP
IO1 + IO2
15mV
0.6A
- ESR · 4 · FS
- 5mΩ · 4 · 1.8MHz
IO
2
IRMS(MAX)
=
= 0.3A
PESR = ESR · IRMS2 = 5mΩ · (0.3A)2 = 0.45mW
w w w . a n a l o g i c t e c h . c o m
18
2784.2007.11.1.1
ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
