ACT88430QJ-T
Rev 1.0, 24-Oct-2018
tion and moves the IC into the OVUVFLT state. This im-
mediately shuts down all regulators including the by-
pass switch. The system restarts in 100ms, following
the programmed startup sequencing. This fault can be
masked with I2C bit UV_nMASK. This fault is latched in
the UV_REG I2C bit. Shutdown due to overcurrent can
also be masked via the I2C bit B1_PG_FLTMSK.
Output Capacitor Selection
The ACT88430 is designed to use small, low ESR, ce-
ramic output capacitors. Buck1 typically requires a 44uF
output capacitor while Buck2, Buck3, and Buck4 require
a 22uF output capacitor each. In order to ensure stabil-
ity, the actual Buck1 capacitance should be greater than
33uF while Buck2, Buck3, and Buck4 should be greater
than 15uF. The output capacitance can be increased to
reduce output voltage ripple and improve load transi-
ents if needed. Design for an output ripple voltage less
than 1% of the output voltage. The following equation
calculates the output voltage ripple as a function of out-
put capacitance.
B1_OV is disabled. There is no overvoltage detection
circuitry on the output of the bypass switch.
Input Capacitor Selection
Each regulator requires a high quality, low-ESR, ce-
ramic input capacitor. Note that even though each buck
converter has separate input pins, all input pins must be
connected to the same voltage potential. 10uF capaci-
tors are typically suitable, but this value can be in-
creased without limit. Smaller capacitor values can be
used with lighter output loads. Choose the input capac-
itor value to keep the input voltage ripple less than
50mV.
∆ꢋꢗ
VRIPPLE
ꢃ
8 ∗ ꢈ ∗ ꢖꢁꢅꢆ
ꢉꢊ
Where ΔIL is the inductor ripple current, FSW is the
switching frequency, and COUT is the output capacitance
after taking DC bias into account.
Be sure to consider the capacitor’s DC bias effects and
maximum ripple current rating when using capacitors
smaller than 0805.
ꢄꢌꢍꢎ
ꢄꢏꢐ
ꢄꢌꢍꢎ
ꢄꢏꢐ
∗ ꢑ1 ꢒ
ꢓ
Vripple ꢃ ꢋꢌꢍꢎ ∗
ꢈꢔꢕ ∗ ꢖꢏꢐ
A capacitor’s actual capacitance is strongly affected by
its DC bias characteristics. The output capacitor is typi-
cally an X5R, X7R, or similar dielectric. Use of Y5U, Z5U,
or similar dielectrics are not recommended due to their
wide variation in capacitance over temperature and volt-
age ranges.
Be sure to consider the capacitor’s DC bias effects and
maximum ripple current rating when using capacitors
smaller than 0805.
A capacitor’s actual capacitance is strongly affected by
its DC bias characteristics. The input capacitor is typi-
cally an X5R, X7R, or similar dielectric. Use of Y5U, Z5U,
or similar dielectrics is not recommended. Input capaci-
tor placement is critical for proper operation. Each
buck’s input capacitor must be placed as close to the IC
as possible. The traces from VIN_Bx to the capacitor
and from the capacitor to PGNDx should as short and
wide as possible.
LDO Converters
General Description
The ACT88430 contains three fully integrated low drop-
out linear regulators (LDO). LDO1 is an 800mA output,
while LDO2 and LDO3 are 200mA outputs. The LDOs
are require only two small external components (Cin,
Cout) for operation. They ship with default output volt-
ages that can be modified via the I2C interface for sys-
tems that require advanced power management func-
tions.
Inductor Selection
The Buck converters utilize current-mode control and a
proprietary internal compensation scheme to simultane-
ously simplify external component selection and opti-
mize transient performance over their full operating
range. The ACT88430 is optimized for operation with
1.0-1.5μH inductors. Choose an inductor with a low DC-
resistance, and avoid inductor saturation by choosing
inductors with DC ratings that exceed the maximum out-
put current by at least 30%. The following equation cal-
culates the inductor ripple current.
LDO1 has a dedicated input pin. LDO2 and LDO3 share
an input pin. The LDOs can operate from different input
voltages than the buck converters. LDO1 and LDO2/3
can operate from different input voltage from each other.
LDO1 has the option to be operated as a standard LDO
or as a load switch.
Enable / Disable Control
ꢄ
ꢑ1 ꢒ ꢁꢅꢆꢓ ∗ ꢄꢁꢅꢆ
ꢄ
ꢇꢂ
When power is applied to the IC, all LDOs automatically
turn on according to a pre-programmed sequence.
Once in normal operation (ACTIVE state), each con-
verter can be independently disabled via I2C. Each CMI
version requires a different set of command to disable a
converter, so contact the factory for specific instructions
∆ꢋꢗ
ꢃ
ꢈ
ꢉꢊ
∗ ꢘ
Where VOUT is the output voltage, VIN is the input voltage,
FSW is the switching frequency, and L is the inductor
value.
Innovative PowerTM
www.active-semi.com
Copyright © 2016-2018 Active-Semi, Inc.
ActiveSwitcherTM is a trademark of Active-Semi.
I2CTM is a trademark of NXP
34
ACTIVE-SEMI [ ACTIVE-SEMI, INC ]
