TPS65130_16 Datasheet, PDF (9/32 Pages) Texas Instruments – Positive and Negative Output DC-DC Converter

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TPS65130, TPS65131
SLVS493D – MARCH 2004 – REVISED JANUARY 2016
Feature Description (continued)
7.3.2 Control
The controller circuits of both converters employ a fixed-frequency, multiple-feedforward controller topology. The
circuits monitor input voltage, output voltage, and voltage drop across the switches. Changes in the operating
conditions of the converters directly affect the duty cycle and must not take the indirect and slow way through the
output voltage control loops. Measurement errors in this feedforward system are corrected by a self-learning
control system. An external capacitor damps the output to avoid output-voltage steps due to output changes of
this selflearning control system.
The voltage loops, determined by the error amplifiers, must only handle small signal errors. The error amplifiers
feature internal compensation. Their inputs are the feedback voltages on the FBP and FBN pins. The device
uses a comparison of these voltages with the internal reference voltage to generate an accurate and stable
output voltage.
7.3.3 Enable
Both converters can be enabled or disabled individually. Applying a logic HIGH signal at the enable pins (ENP for
the boost converter, ENN for the inverting converter) enables the corresponding output. After enabling, internal
circuitry, necessary to operate the specific converter, then turns on, followed by the Soft-Start.
AApplying a low signal at the enable ENP or ENN pin shuts down the corresponding converter. When both
enable pins are low, the device enters shutdown mode, where all internal circuitry turns off. The device now
consumes shutdown current flowing into the VIN pin. The output loads of the converters can be disconnected
from the input, see Load Disconnect.
7.3.4 Load Disconnect
The device supports completely disconnecting the load when the converters are disabled. For the inverting
converter, the device turns off the internal PMOS switch. If the inverting converter is turned off, no DC current
path remains which could discharge the battery or supply.
This is different for the boost converter. The external rectifying diode, together with the boost inductor, form a DC
current path which could discharge the battery or supply if any load connects to the output. The device has no
internal switch to prevent current from flowing. For this reason, the device offers a PMOS gate control output
(BSW) to enable and disable a PMOS switch in this DC current path, ideally directly between the boost inductor
and battery. To be able to fully disconnect the battery, the forward direction of the parasitic backgate diode of this
switch must point to the battery or supply. The external PMOS switch, which connects to BSW, turns on when
the boost converter is enabled and turns off when the boost converter is disabled.
7.3.5 Soft-Start
Both converters have implemented soft-start functions. When each converter is enabled, the implemented switch
current limit ramps up slowly to its nominal programmed value in about 1 ms. Soft-start is implemented to limit
the input current during start-up to avoid high peak currents at the battery which could interfere with other
systems connected to the same battery. Without soft-start, the high input peak current could trigger the
implemented switch current limit, which can lead to a significant voltage drops across the series resistance of the
battery and its connections.
7.3.6 Overvoltage Protection
Both converters (boost and inverter) have implemented individual overvoltage protection. If the feedback voltage
under normal operation exceeds the nominal value by typically 5%, the corresponding converter shuts down
immediately to protect any connected circuitry from possible damage.
7.3.7 Undervoltage Lockout
An undervoltage lockout (UVLO) prevents the device from starting up and operating if the supply voltage at the
VIN pin is lower than the undervoltage lockout threshold. For this case, the device automatically shuts down both
converters when the supply voltage at VIN falls below this threshold. Nevertheless, parts of the control circuits
remain active, which is different than device shutdown.
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