TL75LPXXQ Datasheet, PDF (10/15 Pages) Texas Instruments – LOW-DROPOUT VOLTAGE REGULATORS

TL75LPxxQ SERIES
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TL75LPxxY SERIES
LOWĆDROPOUT VOLTAGE REGULATORS
SLVS073A − SEPTEMBER 1992 − REVISED AUGUST 1995
PARAMETER MEASUREMENT INFORMATION
The TL75LPxx series are low-dropout voltage regulators. This means that the capacitance is important to the
performance of the regulator because it is a vital part of the control loop. The capacitor value and the equivalent series
resistance (ESR) both affect the control loop and must be defined for the load range and the temperature range.
Figures 3 and 4 can establish the capacitance value and ESR range for optimum regulator performance.
Figure 3 shows the recommended range of ESR, measured at 120 Hz, for a given load with a 10-µF capacitor on the
output. In addition, it shows a maximum ESR limit of 2 Ω and a load-dependent minimum ESR limit.
For applications with varying loads, the lightest load condition should be chosen since it is the worst case. Figure 4
shows the relationship of the reciprocal of ESR to the square root of the capacitance with a minimum capacitance
limit of 10 µF and a maximum ESR limit of 2 Ω. Figure 4 establishes the amount that the minimum ESR limit of Figure
3 can be adjusted for different capacitor values. For example, when the minimum load needed is 200 mA,
Figure 3 suggests an ESR range of 0.8 Ω to 2 Ω for 10 µF. Figure 4 shows that changing the capacitor from
10 µF to 400 µF can change the ESR minimum by greater than 3/0.5 (or 6). Therefore, the new minimum ESR value
is 0.8/6 (or 0.13 Ω). This now allows an ESR range of 0.13 Ω to 2 Ω. This expanded ESR range is achieved by using
a larger capacitor at the output. For better stability in low-current applications, it is recommended that a small
resistance be placed in series with the capacitor (see Table 1) so that the ESR better approximates those in
Figures 3 and 4.
Table 1. Compensations for Increased Stability at Low Currents
MANUFACTURER CAPACITANCE
AVX
KEMET
15 µF
33 µF
ESR
TYP
0.9 Ω
0.6 Ω
PART
NUMBER
TAJB156M010S
T491D336M010AS
ADDITIONAL
RESISTANCE
1Ω
0.5 Ω
Applied
Load
Current
Load
Voltage
∆ IL
∆ VL
∆ VL = ∆ IL × ESR
OUTPUT CAPACITOR
OUTPUT CAPACITOR
EQUIVALENT SERIES RESISTANCE
STABILITY
vs
vs
LOAD CURRENT
EQUIVALENT SERIES RESISTANCE
3
0.04
2.8
CL = 10 µF
CI = 0.1 µF
ÇÇ _2.6
ÇÇÇÇÇÇÇÇÇÇÇÇÇ 2.4
2.2
This Region Not
Recommended
for Operation
0.035
0.03
ÇÇÇÇÇÇÇÇÇÇÇÇÇ ₂
ÉÉÉÉÉÉÉÉÉÉÉÉÉÉ ÇÇÇÇÇÇÇÇÇÇÇÇÇ _{MaxESRBoundary}
0.025
1.8
ÉÉÉÉÉÉÉÉÉÉÉÉÉÉ ÇÇÇÇÇÇÇÇÇÇÇÇÇ _1.6
ÉÉÉÉÉÉÉÉÉÉÉÉÉÉ ÇÇÇÇÇÇÇÇÇÇÇÇÇ _1.4
Region of Best Stability
0.02
ÉÉÉÉÉÉÉÉÉÉÉÉÉÉ ÇÇÇÇÇÇÇÇÇÇÇÇÇ 1.2
0.015
1
ÉÉÉÉÉÉÉÉÉÉÉÉÉÉ ÇÇÇÇÇÇÇÇÇÇÇÇÇ _0.8
ÉÉÉÉÉÉÉÉÉÉÉÉÉÉ ÇÇÇÇÇÇÇÇÇÇÇÇÇ _0.6
Min ESR
Boundary
0.01
ÉÉÉÉÉÉÉÉÉÉÉÉÉÉ ÇÇÇÇÇÇÇÇÇÇÇÇÇ _0.4
Potential Instability Region
ÉÉÉÉÉÉÉÉÉÉÉÉÉÉ ÇÇÇÇÇÇÇÇÇÇÇÇÇ _0.2
0.005
10 µF
ÉÉÉÉÉÉÉÉÉÉÉÉÉÉ ÇÇÇÇÇÇÇÇÇÇÇÇÇ 0
0
Not Recommended
Potential Instability
Recommended Min ESR
1000 µF
Region of
Best Stability
400 µF
200 µF
100 µF
22 µF
10 µF
0
0.1
0.2
0.3
0.4
0.5
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
IL − Load Current − A
1/ESR
Figure 3
Figure 4
3−10
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