Datasheet

TPS7A45xx
SLVS720D –JUNE 2008–REVISED AUGUST 2011 www.ti.com
Output Voltage Noise The GND pin current can be found using the GND
Pin Current graphs in Typical Characteristics. Power
The TPS7A45xx regulators have been designed to
dissipation is equal to the sum of the two components
provide low output voltage noise over the 10-Hz to
listed above.
100-kHz bandwidth while operating at full load.
Output voltage noise is typically 35 nV/√Hz over this The TPS7A45xx series regulators have internal
frequency bandwidth for the TPS7A4501 (adjustable thermal limiting designed to protect the device during
version). For higher output voltages (generated by overload conditions. For continuous normal
using a resistor divider), the output voltage noise is conditions, the maximum junction temperature rating
gained up accordingly. This results in RMS noise of 125°C must not be exceeded. It is important to
over the 10-Hz to 100-kHz bandwidth of 14 μV
RMS
for give careful consideration to all sources of thermal
the TPS7A4501, increasing to 38 μV
RMS
for the resistance from junction to ambient. Additional heat
TPS7A4533. sources mounted nearby must also be considered.
Higher values of output voltage noise may be For surface-mount devices, heat sinking is
measured when care is not exercised with regard to accomplished by using the heat-spreading
circuit layout and testing. Crosstalk from nearby capabilities of the PC board and its copper traces.
traces can induce unwanted noise onto the output of Copper board stiffeners and plated through-holes can
the TPS7A45xx. Power-supply ripple rejection must also be used to spread the heat generated by power
also be considered; the TPS7A45xx regulators do not devices.
have unlimited power-supply rejection and pass a
Table 1 lists thermal resistance for several different
small portion of the input noise through to the output.
board sizes and copper areas. All measurements
were taken in still air on 1/16" FR-4 board with 1-oz
Thermal Considerations
copper.
The power handling capability of the device is limited
Table 1. Thermal Data
by the maximum rated junction temperature (125°C).
The power dissipated by the device is made up of
COPPER AREA THERMAL
two components:
BOARD RESISTANCE
AREA (JUNCTION TO
TOPSIDE
(1)
BACKSIDE
1. Output current multiplied by the input/output
AMBIENT)
voltage differential: I
OUT
(V
IN
– V
OUT
)
KTT Package (5-Pin TO-263)
2. GND pin current multiplied by the input voltage:
2500 mm
2
2500 mm
2
2500 mm
2
23°C/W
I
GND
V
IN
.
1000 mm
2
2500 mm
2
2500 mm
2
25°C/W
125 mm
2
2500 mm
2
2500 mm
2
33°C/W
(1) Device is mounted on topside.
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