ZHCSBT7D May 2013 – April 2017 TPS7A7002
PRODUCTION DATA.
7 Detailed Description
7.1 Overview
The TPS7A7002 offers a high current supply with very-low dropout voltage. The TPS7A7002 is designed to minimize the required component count for a simple, small-size, and low-cost solution.
7.2 Functional Block Diagram
Figure 7. Adjustable Output Voltage Version
7.3 Feature Description
7.3.1 Internal Current Limit
The TPS7A7002 internal current limit helps protect the regulator during fault conditions. During a current limit condition, the output sources a fixed amount of current largely independent of output voltage. For reliable operation, do not operate the device in a current limit state for an extended period of time.
Powering on the device with the enable pin, or increasing the input voltage above the minimum operating voltage while a low-impedance short exists on the output of the device, may result in a sequence of high-current pulses from the input to the output of the device. The energy consumed by the device is minimal during these events; therefore, there is no failure risk. Additional input capacitance helps to mitigate the load transient requirement of the upstream supply during these events.
7.3.2 Enable (EN)
The enable pin (EN) is an active-high logic input. When it is logic low, the device turns off, and the consumption current is less than 1 µA. When it is logic high, the device turns on. The EN pin must be connected to a logic high or logic low level.
When the enable function is not required, connect EN to IN.
7.4 Device Functional Modes
Table 1 provides a quick comparison between the normal, dropout, and disabled modes of operation.
Table 1. Device Functional Mode Comparison
| OPERATING MODE | PARAMETER | |||
|---|---|---|---|---|
| VIN | EN | IOUT | TJ | |
| Normal | VIN > VOUT(nom) + VDO | VEN > VEN(HI) | IOUT < ICL | TJ < TSD |
| Dropout | VIN < VOUT(nom) + VDO | VEN > VEN(HI) | IOUT < ICL | TJ < TSD |
| Disabled | — | VEN < VEN(LO) | — | TJ > TSD |
7.4.1 Normal Operation
The device regulates to the nominal output voltage under the following conditions:
- The input voltage is greater than the nominal output voltage plus the dropout voltage (VOUT(nom) + VDO).
- The enable voltage has previously exceeded the enable rising threshold voltage and not yet decreased below the enable falling threshold.
- The output current is less than the current limit (IOUT < ICL).
- The device junction temperature is less than the thermal shutdown temperature (TJ < TSD).
7.4.2 Dropout Operation
If the input voltage is lower than the nominal output voltage plus the specified dropout voltage, but all other conditions are met for normal operation, the device operates in dropout mode. In this mode, the output voltage tracks the input voltage. During this mode, the transient performance of the device becomes significantly degraded because the pass device is in a triode state and no longer controls the current through the LDO. Line or load transients in dropout can result in large output-voltage deviations.