ADP1821
Rev. C | Page 21 of 24
APPLICATION CIRCUITS
The ADP1821 controller can be configured to regulate an output
with a load of more than 20 A if the power components, such as
the inductor, MOSFETs, and the bulk capacitors are chosen
carefully to meet the power requirement. The maximum load
and power dissipation are limited by the power-train compo-
nents. Figure 1 shows a typical application circuit that can drive
an output load of 20 A. Note that two low-side MOSFETs are
needed to deliver the 20 A load. In this example, two power rails
are needed: a 5 V bias supply, which needs to supply about 30
mA to power the ADP1821 at full load, and a power input rail,
which ranges from 2.5 V to 20 V. The bulk input and output
capacitors used in this example are Sanyo OSCON™ capacitors,
which have low ESR and high current ripple rating. An alternative
to the OSCON capacitors are the polymer aluminum capacitors
that are available from other manufacturers such as United
Chemi-Con. Aluminum electrolytic capacitors, such as the
Rubycon ZLG low-ESR series, can also be paralleled up at the
input or output to meet the current ripple requirement. Because
the aluminum electrolytic capacitors have higher ESR and much
larger variation in capacitance over the operating temperature
range, a larger bulk input and output capacitance is needed to
reduce the effective ESR and suppress the current ripple.
The ADP1821 can be configured to drive an output load of
less than 1 A.
Figure 22 shows a typical application circuit that
drives a 3 A load in an all multilayer ceramic capacitor (MLCC)
solution. Notice that the two MOSFETs used in this example are
dual-channel MOSFETs in a PowerPAK® SO-8 package, which
reduces cost and saves layout space.
GND
PVCC
ADP1821
SHDN
VCC
BST
DH
SW
CSL
DL
PGND
FB
FREQ
SYNC
PWGD
COMP
SS
1µF
1µF
10Ω
2kΩ
4.1kΩ
84.5Ω
1kΩ
100kΩ
M1
M2
L1 = 2.2µH
OUTPUT
1.8V, 3A
IN = 3.7V TO 5.5V
D1
AGND
100nF
6.65kΩ
1.5nF
120pF
0.22µF
+
C
IN1
1µF
10V
+
C
IN2
10µF
10V
×2
C
OUT1
1µF
10V
C
OUT2
47µF
6.3V
C
OUT3
100µF
6.3V
8.2nF
f
SW
= 600kHz
C
IN2
: MURATA, GRM21BR61A106K
C
OUT3
: MURATA, GRM31CR60J107M
M1, M2: VISHAY, DUAL-CHANNEL MOSFET Si7940DP
L1: TOKO, FDV0620-2R2M
C
OUT2
: MURATA, GRM31CR60J476M
D1: VISHAY BAT54
5310-021
Figure 22. Typical Application Circuit with all Multilayer Ceramic Capacitors (MLCC), 3.3 V to 5 V Input
