TPS40422 Datasheet, PDF (17/54 Pages) Texas Instruments – Dual-Output or Two-Phase Synchronous Buck Controller with PMBus

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TPS40422
SLUSAQ4C – OCTOBER 2011 – REVISED AUGUST 2012
The TPS40422 implements cycle-by-cycle current limit when the peak sensed current exceeds the set threshold.
In a time constant matched current sensor network, the signal across the CSxP and CSxN pins has both dc and
ac inductor current information, so overcurrent trips when the dc current plus half of the ripple current exceeds
the set threshold. When the time constant is not well-matched, the dc current which trips the overcurrent changes
accordingly.
When the controller counts three consecutive clock cycles of an overcurrent condition, the high-side and low-side
MOSFETs are turned off and the controller enters hiccup mode or latches the output off, depending on the
IOUT_OC_FAULT_RESPONSE register. In continuous restart hiccup mode, after seven soft-start cycles, normal
switching is attempted. If the overcurrent has cleared, normal operation resumes; otherwise, the sequence
repeats.
Two-Phase Mode and Current Sharing Loop
The TPS40422 can be configured to operate in single-output two-phase mode for high-current applications. With
proper selection of the external MOSFETs, this device can support up to 50-A of load current in a two-phase
configuration. As shown in Figure 13, to configure TPS40422 as two-phase mode, FB2 is tied to BP6. In this
mode, COMP1 must be connected to COMP2 to ensure current sharing between the two phases. For high-
current applications, the remote sense amplifier is used to compensate for the parasitic offset to provide an
accurate output voltage. DIFFO1, which is the output of the remote sensing amplifier, is connected to the resistor
divider of the feedback network.
Power Stage
R_{PARASITIC VSNS}
R
R
+
R
COMP2
COMP1
FB2
BP6
VSNS1
GSNS1
L
O
A
D
R_PARASITIC
GSNS
R
DIFFO1
+ VREF
FB1
COMP1
Figure 13. Two-Phase Mode Configuration
UDG-11249
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