TPS43330-Q1 Datasheet, PDF (19/35 Pages) Texas Instruments – LOW IQ, SINGLE BOOST, DUAL SYNCHRONOUS BUCK CONTROLLER

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Gate Driver Supply (VREG, EXTSUP)
The gate drivers of the buck and boost controllers are
supplied from an internal linear regulator whose
output (5.8V typical) is available at the VREG pin and
should be decoupled using at least a 1µF ceramic
capacitor. This pin has an internal current limit
protection and should not be used to power any other
circuits.
The VREG linear regulator is powered from VIN by
default when the EXTSUP voltage is lower than 4.6V
(typ.). In case VIN expected to go to high levels,
there can be excessive power dissipation in this
regulator, especially at high switching frequencies
and when using large external MOSFET's. In this
case, it is advantageous to power this regulator from
the EXTSUP pin which can be connected to a supply
lower than VIN but high enough to provide the gate
drive. When EXTSUP is connected to a voltage
greater than 4.6V, the linear regulator automatically
switches to EXTSUP as its input to provide this
advantage. Efficiency improvements are possible
when one of the switching regulator rails from the
TPS43330/2 or any other voltage available in the
system is used to power the EXTSUP. The maximum
voltage that should be applied to EXTSUP is 13V.
Using a large value for EXTSUP is advantageous as
it provides a large gate drive and hence better
on-resistance of the external MOSFET's. A 0.1µF
ceramic capacitor is recommended for decoupling the
EXTSUP pin when not being used.
During low power mode, the EXTSUP functionality is
not available. The internal regulator operates as a
shunt regulator powered from VIN and has a typical
value of 7.5V. Current limit protection for VREG is
available in low power mode as well.
External P-Channel Drive (GC2) and Reverse
Battery Protection
The TPS43330/2 includes a gate driver for an
external P-channel MOSFET which can be connected
across the rectifier diode of the boost regulator. This
is useful to reduce power losses when the boost
controller is not switching. The gate driver provides a
swing of 6V typical below the VIN voltage in order to
drive a P-channel MOSFET. When VBAT falls below
the boost enable threshold, the gate driver turns off
the P-channel MOSFET and the diode is no longer
bypassed.
The gate driver can also be used to bypass any
additional protection diodes connected in series as
shown in Figure 23. Figure 24 also shows a different
scheme of reverse battery protection which may
require only a smaller sized diode to protect the
N-channel MOSFET as it conducts only for a part of
the switching cycle. Since it is not always in series
path, the system efficiency can be improved.
TPS43330-Q1
TPS43332-Q1
SLVSA82A – MARCH 2011 – REVISED NOVEMBER 2011
Vbat
Q7
Fuse (S1)
D2
R10
D3
C16 C17
Q6
L3
D1 C15
GC2 _TPS43330/2
VIN
C14
C13
R9
DS
GC1
COMPC
VBAT
Figure 23. Reverse Battery Protection Option for
Buck Boost Configuration
GC2
VBAT
Fuse
VIN
TPS43330/2
DS
GC1
COMPC
VBAT
Figure 24. Reverse Battery Protection Option for
Buck Boost Configuration
Undervoltage Lockout and Overvoltage
Protection
The TPS43330/2 starts up at a VIN voltage of 6.5V
(min). Once it has started up, the device operates
down to a VIN voltage of 3.6V, below this voltage
level the undervoltage lockout will disable the device.
A voltage of 46V at VIN triggers the overvoltage
comparator which shuts down the device. In order to
prevent that transient spikes shutting down the
device, the under and overvoltage protection have
filter times of 5µs (typical).
When the voltages return to the normal operating
region, the enabled switching regulators start
including a new soft-start ramp for the buck
regulators.
When the boost controller is enabled, a voltage less
than 1.9V (typical) on VBAT triggers an undervoltage
lockout and pulls the boost gate driver (GC1) low. As
a result VIN will fall at a rate dependent on its
capacitor and load, eventually triggering VIN
undervoltage. A short falling transient at VBAT even
lower than 2V can thus be survived, if VBAT returns
to higher than 2.5V before VIN is discharged to the
undervoltage threshold. This detection has a filter
delay of 5µsec typical.
Copyright © 2011, Texas Instruments Incorporated
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Product Folder Link(s): TPS43330-Q1 TPS43332-Q1