Datasheet

TPS755xx and TPS757xx Families of LDO Regulators
1-2
Introduction
1.1 TPS755xx and TPS757xx Families of LDO Regulators
Like all LDO linear regulators, the TPS755xx and TPS757xx families of LDO
regulators use a series pass element and feedback network, including an error
amplifier and voltage reference, to provide a regulated output voltage from
a slightly higher, possibly varying input voltage. The distinguishing
characteristics of these regulators include high current output, low dropout and
integrated power good. Specific capabilities of these regulators include:
- 5-A (TPS755xx) and 3-A (TPS757xx) maximum load current
- Both families are available in 1.5-V, 1.8-V, 2.5-V, 3.3-V, and adjustable with
active low enable (EN
)
- Very low dropout voltage (250 mV at 5 A for the TPS75533)
- Active low power good (PG) signal
- Available in either TO-220 or TO-263 packages for maximum power
dissipation capability
1.2 EVM Design Strategy
Power-up sequencing is recommended when powering the core and I/O
power supply rails in many DSP, microcontroller, and FPGA applications.
Designing a system without proper sequencing can result in two types of faults.
The first type represents a threat to the long-term reliability of the dual voltage
device. The second can cause faults in and possible permanent damage to the
I/O ports of the processor or the supporting system devices. Through jumper
selections, the two regulators on this EVM have been configured to perform
power-up sequencing. The active low power good (PG
) output of the
TPS75525 2.5-V regulator has been tied to the active low enable (EN
) input
of the TPS75733 3.3-V regulator. Therefore, the 3.3-V regulator will not be
enabled until the 2.5-V regulator is within approximately 90% of its regulated
voltage. A high current Schottky diode has been placed between the two
voltage rails so that the 2.5-V rail will pull the 3.3-V rail up to 2.5 V until the 3.3-V
regulator is enabled.
The EVM board can be used to perform other tests. The jumpers can be
changed as indicated in Table 1–1 so that each regulator can be separately
enabled and/or disabled. U1 and U2 can be replaced with any of the
TPS755xx, TPS756xx, TPS757xx, TPS758xx, and TPS759xx fixed regulator
options. As per Table 1–1, changing JP4 causes resistors R4 and R5 to
become usable and U1 can be replaced with one of TPS75x01 adjustable
voltage option regulators. Note that diode D1 may need to be removed if the
output voltage of U1 is larger than the output voltage of U3 by more than 0.3 V.
The board has been designed to accommodate either the TO-220 (KC) and
TO-263 PowerFlex (KTT) packages, but not both at the same time. The
TO-263 packages have been installed on this EVM and soldered to the ground
plane area on both the top and bottom layers of the board for heat sinking.
Refer to the TPS755xx and TPS757xx data sheets for the maximum power
dissipation capabilities of the TO-263 packages. If the TO-263 packages are
replaced with TO-220 packages, appropriate heat sinks will have to be
attached to the TO-220 packages to achieve comparable power dissipation.