8.1.1 Input and Output Capacitor Requirements

Recommended capacitors are 1.0-μF X5R- and X7R-type ceramic because these capacitors have minimal variation in value and equivalent series resistance (ESR) over temperature.

However, the TLV700xx-Q1 is designed to be stable with an effective capacitance of 0.1 μF or larger at the output. Thus, the device is stable with capacitors of other dielectric types as well, as long as the effective capacitance under operating bias voltage and temperature is greater than 0.1 μF. This effective capacitance refers to the capacitance that the LDO sees under operating bias voltage and temperature conditions; that is, the capacitance after taking both bias voltage and temperature derating into consideration. In addition to allowing the use of cheaper dielectrics, this capability of being stable with 0.1-μF effective capacitance also enables the use of smaller-footprint capacitors that have higher derating in size- and space-constrained applications.

Note that using a 0.1-μF rated capacitor at the output of the LDO does not ensure stability because the effective capacitance under the specified operating conditions would be less than 0.1 μF. Maximum ESR should be less than 200 mΩ.

Although an input capacitor is not required for stability, it is good analog design practice to connect a 0.1-μF to 1-μF, low-ESR capacitor across the IN pin and GND in of the regulator. This capacitor counteracts reactive input sources and improves transient response, noise rejection, and ripple rejection. A higher-value capacitor may be necessary if large, fast-rise-time load transients are anticipated, or if the device is not located close to the power source. If source impedance is more than 2 Ω, a 0.1-μF input capacitor may be necessary to ensure stability.

High-ESR capacitors may degrade PSRR performance.

8.1.2 Transient Response

As with any regulator, increasing the size of the output capacitor reduces over- and undershoot magnitude but increases the duration of the transient response.

8.1.3 Thermal Information

Thermal protection disables the output when the junction temperature rises to approximately 160°C, allowing the device to cool. When the junction temperature cools to approximately 140°C, the output circuitry is again enabled. Depending on power dissipation, thermal resistance, and ambient temperature, the thermal protection circuit may cycle on and off. This cycling limits the dissipation of the regulator, protecting it from damage as a result of overheating.

Any tendency to activate the thermal protection circuit indicates excessive power dissipation or an inadequate heatsink. For reliable operation, junction temperature should be limited to 125°C maximum. To estimate the margin of safety in a complete design (including heatsink), increase the ambient temperature until the thermal protection is triggered; use worst-case loads and signal conditions. For good reliability, thermal protection should trigger at least 35°C above the maximum expected ambient condition of the particular application. This configuration produces a worst-case junction temperature of 125°C at the highest expected ambient temperature and worst-case load.

The internal protection circuitry of the TLV700xx-Q1 has been designed to protect against overload conditions. It was not intended to replace proper heatsinking. Continuously running the TLV700xx-Q1 into thermal shutdown degrades device reliability.

8.2.1 Design Requirements

Table 1 shows example design parameters and values for this typical application.

8.2.2 Detailed Design Procedure

8.2.2.3 Thermal Calculation

See Equation 1 for thermal calculation.

Equation 1.

where:

• P_D = continuous power dissipation
• I_OUT = output current
• V_IN = input voltage
• V_OUT = output voltage
• Because I_Q << I_OUT, the term I_Q x V_IN is always ignored.

For a device under operation at a given ambient air temperature (T_A), use Equation 2 to calculate the junction temperature (T_J).

Equation 2.

where:

• R_θJA = junction-to-ambient air thermal impedance

Use Equation 3 to calculate the rise in junction temperature because of power dissipation.

Equation 3.

For a given maximum junction temperature (T_Jmax), use Equation 4 to calculate the maximum ambient air temperature (T_Amax) at which the device can operate.

Equation 4.

8.2.3 Application Curve

Figure 23. Power Up