FEATURES
• Two-, Three-, or Four-Phase Operation
• 5-V to 15-V Operating Range
• Programmable Switching Frequency Up to
1-MHz/Phase
• Current Mode Control With Forced Current
Sharing(1)
(1) Patent pending.
• 1% Internal 0.7-V Reference
• Resistive Divider Set Output Voltage
• True Remote Sensing Differential Amplifier
• Resistive or DCR Current Sensing
• Current Sense Fault Protection
• Programmable Load Line
• Compatible with UCC37222 Predictive Gate
Drive™ Technology Drivers
• 24-Pin Space-Saving TSSOP Package
• 28-Pin QFN Package
• TPS40090: Binary Outputs
• TPS40091: 3-State Outputs

APPLICATIONS
• Internet Servers
• Network Equipment
• Telecommunications Equipment
• DC Power Distributed Systems

DESCRIPTION
The TPS4009x is a two-, three-, or four-phase programmable synchronous buck controller that is optimized for
low-voltage, high-current applications powered by a 5-V to 15-V distributed supply. A multi-phase converter offers
several advantages over a single power stage including lower current ripple on the input and output capacitors,
faster transient response to load steps, improved power handling capabilities, and higher system efficiency.
Each phase can be operated at a switching frequency up to 1-MHz, resulting in an effective ripple frequency of
up to 4-MHz at the input and the output in a four-phase application. A two-phase design operates 180 degrees
out-of-phase, a three-phase design operates 120 degrees out-of-phase, and a four-phase design operates 90
degrees out-of-phase as shown in Figure 1.
The number of phases is programmed by connecting the de-activated phase PWM output to the output of the
internal 5-V LDO. In two-phase operation the even phase outputs should be de-activated.
The TPS4009x uses fixed frequency, peak current mode control with forced phase current balancing. When
compared to voltage mode control, current mode results in a simplified feedback network and reduced input line
sensitivity. Phase current is sensed by using either current sense resistors installed in series with output
inductors or, for improved efficiency, by using the DCR (direct current resistance) of the filter inductors. The latter
method involves generation of a current proportional signal with an R-C circuit (shown in Figure 10).
The R-C values are selected by matching the time constants of the R-C circuit and the inductor; R-C = L/DCR.
With either current sense method, the current signal is amplified and superimposed on the amplified voltage error
signal to provide current mode PWM control.
An output voltage droop can be programmed to improve the transient window and reduce size of the output filter.
Other features include a single voltage operation, a true differential sense amplifier, a programmable current
limit, soft-start and a power good indicator.