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THEORY OF OPERATION
POWER SUPPLIES
To facilitate system design, the TAS5186 needs only
a
12-V
supply
in
addition
power-stage supply. An internal voltage regulator
provides suitable voltage levels for the digital and
low-voltage analog circuitry. Additionally, all circuitry
requiring a floating voltage supply, e.g., the high-side
gate drive, is accommodated by built-in bootstrap
circuitry requiring only a few external capacitors.
SYSTEM POWER-UP/DOWN SEQUENCE
The TAS5186 does not require a power-up sequence.
The
outputs
of
the
high-impedance state until the gate-drive supply volt-
age (GVDD_X) and VDD voltage are above the
undervoltage protection (UVP) voltage threshold (see
the
Electrical Characteristics
section of this data
sheet). Although not specifically required, it is rec-
ommended to hold RESET in a low state while
powering up the device.
Powering Down
Error Reporting
TAS5186
SLES136–MAY 2005
decoupled with a 100-nF ceramic capacitor placed as
close as possible to each supply pin on the same
side of the PCB as the TAS5186. It is recommended
to follow the PCB layout of the TAS5186 reference
design.
For
additional
information
ommended power supply and required components,
see the application diagrams given in this data sheet.
The
12-V
supply
should
low-noise, low-output-impedance voltage regulator.
Likewise, the 39-V power-stage supply is assumed to
have low output impedance and low noise. The
power-supply sequence is not critical due to the
internal
power-on-reset
TAS5186
is
fully
protected
power-stage turnon due to parasitic gate charging.
Thus, voltage-supply ramp rates (dv/dt) are typically
noncritical.
to
a
typical
39-V
on
the
rec-
be
powered
from
a
In order to provide outstanding electrical and acoustic
characteristics, the PWM signal path including gate
drive and output stage is designed as identical,
independent half-bridges. For this reason, each
half-bridge has separate bootstrap pins (BST_X) and
power-stage supply pins (PVDD_X). Furthermore, an
additional pin (VDD) is provided as power supply for
all common circuits. Although supplied from the same
12-V source, it is highly recommended to separate
GVDD_X and VDD on the printed-circuit board (PCB)
by RC filters (see application diagram for details).
These
RC
filters
provide
high-frequency isolation. Special attention should be
paid to placing all decoupling capacitors as close to
their associated pins as possible. In general, induct-
ance between the power-supply pins and decoupling
capacitors must be avoided. (See reference board
documentation for additional information.)
circuit.
Moreover,
against
the
erroneous
H-bridge
remain
in
a
the
recommended
When the TAS5186 is being used with TI PWM
modulators such as the TAS5086, no special atten-
tion to the state of RESET is required, provided that
the chipset is configured as recommended.
For a properly functioning bootstrap circuit, a small
ceramic capacitor must be connected from each
bootstrap pin (BST_X) to the power-stage output pin
(OUT_X). When the power-stage output is low, the
bootstrap capacitor is charged through an internal
diode
connected
between
power-supply pin (GVDD_X) and the bootstrap pin.
When the power-stage output voltage is high, the
bootstrap capacitor voltage is shifted above the
output voltage potential and thus provides a suitable
voltage supply for the high-side gate driver. In an
application with PWM switching frequencies in the
range 352 kHz to 384 kHz, it is recommended to use
33-nF ceramic capacitors, size 0603 or 0805, for the
bootstrap capacitor. These 33-nF capacitors ensure
sufficient energy storage, even during minimal PWM
duty cycles, to keep the high-side power stage FET
(LDMOS) fully started during all of the remaining part
of the PWM cycle. In an application running at a
reduced switching frequency, generally 250 kHz to
192 kHz, the bootstrap capacitor might need to be
increased in value. Special attention should be paid
to the power-stage power supply; this includes
component selection, PCB placement and routing. As
indicated,
each
half-bridge
power-stage supply pins (PVDD_X). For optimal elec-
trical performance, EMI compliance, and system re-
liability it is important that each PVDD_X pin is
the
gate-drive
The TAS5186 does not require a power-down se-
quence. The device remains fully operational as long
as the gate-drive supply (GVDD_X) voltage and VDD
voltage are above the undervoltage protection (UVP)
threshold level (see the
Electrical Characteristics
section of this data sheet). Although not specifically
required, it is a good practice to hold RESET low
during power down, thus preventing audible artifacts
including pops and clicks
When the TAS5186 is being used with TI PWM
modulators such as the TAS5086, no special atten-
tion to the state of RESET is required, provided that
the chipset is configured as recommended.
The
open-drain outputs. Their function is for protec-
tion-mode signaling to a PWM controller or other
system-control device.
SD
and
OTW
pins
are
both
active-low,
has
independent
12