RT9058-50GX Просмотр технического описания (PDF) - Richtek Technology
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RT9058-50GX Datasheet PDF : 9 Pages
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Applications Information
Like any low dropout linear regulator, the RT9058's external
input and output capacitors must be properly selected for
stability and performance. Use a 1μF or larger input
capacitor and place it close to the IC's VCC and GND pins.
Any output capacitor meeting the minimum 1mΩ ESR
(Equivalent Series Resistance) requirement may be used.
Place the output capacitor close to the IC's VOUT and
GND pins. Increasing capacitance and decreasing ESR
can improve the circuit's PSRR and line transient response.
Thermal Considerations
For continuous operation, do not exceed absolute the
maximum junction temperature. The maximum power
dissipation depends on the thermal resistance of the IC
package, PCB layout, rate of surrounding airflow, and the
allowed difference between the junction and ambient
temperatures. The maximum power dissipation can be
calculated by the following formula :
PD(MAX) = (TJ(MAX) − TA) / θJA
where TJ(MAX) is the maximum junction temperature, TA is
the ambient temperature, and θJA is the junction to ambient
thermal resistance.
The recommended operating conditions specify a
maximum junction temperature is 125°C. The junction to
ambient thermal resistance, θJA, is layout dependent. On
a standard JEDEC 51-7 four-layer thermal test board ,
the thermal resistance, θJA, of the SOT-23-3 package is
243.3°C/W. For the SOT-89-3 package, the θJA, is
167.7°C/W. The maximum power dissipation at TA = 25°C
can be calculated by the following formula :
PD(MAX) = (125°C − 25°C) / (243.3°C/W) = 0.41W for
SOT-23-3 package
PD(MAX) = (125°C − 25°C) / (167.7°C/W) = 0.6W for
SOT-89-3 package
For a fixed TJ(MAX) of 125°C, the maximum power
dissipation depends on the operating ambient temperature
and the package's thermal resistance, θJA. The derating
curve in Figure 1 shows the effect of rising ambient
temperature on the maximum recommended power
dissipation.
RT9058
0.7
SOT-89-3
0.6
Four-Layer PCB
0.5
SOT-23-3
0.4
0.3
0.2
0.1
0.0
0
25
50
75
100
125
Ambient Temperature (°C)
Figure 1. Derating Curve of Maximum Power Dissipation
Copyright ©2013 Richtek Technology Corporation. All rights reserved.
DS9058-00 April 2013
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
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