Datasheet

Applied Load
Current
Load
Voltage
∆V
L
∆I
L
∆V
L
= ∆I
L
× ESR
0 1 2 3 4 54.53.52.51.50.5
0
0.01
0.015
0.02
0.025
0.03
0.035
0.04
200 µF
1000 µF
1/ESR
0.005
400 µF
Not Recommended
Recommended Min ESR
Potential Instability
Region of
Best Stability
100 µF
22 µF
10 µF
C
L
Stability −
Max ESR Boundary
Region of Best Stability
Min ESR
Boundary
3
2.8
2.6
2.4
2.2
2
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
0.10 0.2 0.3 0.4 0.5
I
L
− Load Current Range − A
This Region Not
Recommended for
Operation
C
L
= 10 µF
C
I
= 0.1 µF
f = 120 Hz
Potential Instability Region
Equivalent Series Resistance (ESR) − Ω
TL750M SERIES
SLVS021M –JANUARY 1988–REVISED OCTOBER 2009............................................................................................................................................. www.ti.com
PARAMETER MEASUREMENT INFORMATION
The TL750Mxx is a low-dropout regulator. This means that the capacitance loading 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. Figure 1 and Figure 2 can establish the capacitance value and ESR range for the best regulator
performance.
Figure 1 shows the recommended range of ESR for a given load with a 10-μF capacitor on the output. This
figure also 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 because it is the worst case.
Figure 2 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. This figure establishes the amount that the minimum
ESR limit shown in Figure 1 can be adjusted for different capacitor values.
For example, where the minimum load needed is 200 mA, Figure 1 suggests an ESR range of 0.8 Ω to 2 Ω for
10 μF. Figure 2 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 allows an ESR range
of 0.13 Ω to 2 Ω , achieving an expanded ESR range by using a larger capacitor at the output. For better stability
in low-current applications, a small resistance placed in series with the capacitor (see Table 1) is recommended,
so that ESRs better approximate those shown in Figure 1 and Figure 2.
Table 1. Compensation for Increased Stability at Low Currents
MANUFACTUR ESR PART ADDITIONAL
CAPACITANCE
ER TYP NUMBER RESISTANCE
<br/>
AVX 15 μF 0.9 Ω TAJB156M010S 1 Ω
<br/>
<br/>
T491D336M010
KEMET 33 μF 0.6 Ω 0.5 Ω
AS
<br/>
OUTPUT CAPACITOR <br/>
EQUIVALENT SERIES RESISTANCE (ESR) STABILITY
vs vs
LOAD CURRENT RANGE EQUIVALENT SERIES RESISTANCE (ESR)
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