TL750M Datasheet, PDF (6/20 Pages) Texas Instruments – LOW-DROPOUT VOLTAGE REGULATORS

TL750M SERIES, TL751M SERIES
LOW-DROPOUT VOLTAGE REGULATORS
SLVS021K – JANUARY 1988 – REVISED OCTOBER 2006
PARAMETER MEASUREMENT INFORMATION
www.ti.com
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
MANUFACTURER CAPACITANCE
<br/>
AVX
<br/>
<br/>
KEMET
<br/>
15 µF
33 µF
ESR
TYP
PART
NUMBER
0.9 Ω TAJB156M010S
ADDITIONAL
RESISTANCE
1Ω
0.6 Ω T491D336M010AS
0.5 Ω
Applied Load
Current
Load
Voltage
∆I_L
∆V_L
∆V_L = ∆I_L × ESR
OUTPUT CAPACITOR
EQUIVALENT SERIES RESISTANCE (ESR)
vs
LOAD CURRENT RANGE
3
2.8 CL = 10 µF
22211110000..........._{ÎÎÎÎÎÎÎÎÎÎÎ21064286428642 ÎÎÎÎÎÎÎÎÎÎÎÏÏÏ}^Cf=I_{P=ÎÎÎÎÎÎÎÎÎÎÎÏÏÏ1o20te0.1nÎÎÎÎÎÎÎÎÎÎÎÏÏÏHt}^µ_{izaFlÎÎÎÎÎÎÎÎÎÎÎÏÏÏInstaÎÎÎÎÎÎÎÎÎÎÎÏÏÏÏÏÏÏbRileitÎÎÎÎÎÎÎÎÎÎÎÏÏÏÏÏÏÏgyTROioRhepniceeÎÎÎÎÎÎÎÎÎÎÎÏÏÏÏÏÏÏÏÏ}^{sogroRamifoteMBimn}_{ÎÎÎÎÎÎÎÎÎÎÎÏÏÏÏÏÏÏÏÏogeaniesoxntnEdÎÎÎÎÎÎÎÎÎÎÎÏÏÏÏÏÏÏÏÏÏSNeStdaRobtÎÎÎÎÎÎÎÎÎÎÎÏÏÏÏÏÏÏÏÏfMBBoiloiriotnuyuÎÎÎÎÎÎÎÎÎÎÎÏÏÏÏÏÏÏÏÏnEndSdaaRÎÎÎÎÎÎÎÎÎÎÎÏÏÏÏÏÏÏÏrryy ÎÎÎÎÎÎÎÎÎÎÎÏÏÏÏ}
0
0.1
0.2
0.3
0.4
0.5
I_L − Load Current Range − A
Figure 1.
<br/>
STABILITY
ÎÎ 0.04
ÎÎÎÎÎÎÎÎÎÎÏÎÏÎÏ _0.035
ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÏÏÎÎÏÏÎÎÏÏ _0.03
ÎÎÎÎÎÎÏÎÏÎÏÎÎÎÎ _0.025
ÎÎÎÎÎÎÎÎÏÎÎÏÎÎÏÏÎÎÏÏÎÎÏÏÎÎÎÎÎÎÎÎ _0.02
vs
EQUIVALENT SERIES RESISTANCE (ESR)
Not Recommended
Recommended Min ESR
Potential Instability
1000 µF
Region of
Best Stability
400 µF
ÎÎÎÎÏÏÎÎÏÏÎÎÏÏÎÎÏÏÎÎÏÏÎÎÎÎÎÎÎÎÎÎÎÎ _0.015
ÎÎÏÎÏÎÏÎÎÎÎÎÎÎÎ _0.01
200 µF
100 µF
ÎÎÏÏÎÎÏÏÎÎÏÏÎÎÏÏÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ _0.005
22 µF
ÎÏÎÏÎÏÎÏÎÎÎÎÎÎÎÎ 10 µF
0
ÏÏÏ _{0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5}
1/ESR
Figure 2.
6
Submit Documentation Feedback