LP2966IMMX-3325 Datasheet, PDF (12/21 Pages) Texas Instruments – Dual 150mA Ultra Low-Dropout Regulator

LP2966
SNVS028E – APRIL 2000 – REVISED APRIL 2013
www.ti.com
The primary source of noise in low-dropout regulators is the internal reference. In CMOS regulators, noise has a
low frequency component and a high frequency component, which storngly depend on the silicon area and
quiescent current. Noise can be reduced in two ways: by increasing the transistor area or by increasing the
current drawn by the internal reference. Increasing the area will increase the die size and decreases the chance
of fitting the die into a small package. Increasing the current drawn by the internal reference increases the total
supply current (ground pin current) of the IC. Using an optimized trade-off of ground pin current and die size,
LP2966 achieves low noise performance with low quiescent current in an VSSOP-8 package.
Short-Circuit Foldback Protection
In the presence of a short or excessive load current condition, the LP2966 uses an internal short circuit foldback
mechanism that regulates the maximum deliverable output current. A strong negative temperature coefficient is
designed into the circuit to enable extremely higher peak output current capability (in excess of 400mA per output
at room temperature, see TYPICAL PERFORMANCE CHARACTERISTICS ). Thus, a system designer using the
LP2966 can achieve higher peak output current capability in applications where the LP2966 internal junction
temperature is kept below 125°C. Refer to APPLICATIONS INFORMATION on calculating the maximum output
current capability of the LP2966 for your application.
Error Flag Operation
The LP2966 produces a logic low signal at the Error Flag pin (ERROR) when the corresponding output drops out
of regulation due to low input voltage, current limiting, or thermal limiting. This flag has a built in Hysteresis. The
timing diagram in Figure 32 shows the relationship between the ERROR and the output voltage. In this example,
the input voltage is changed to demonstrate the functionality of the Error Flag.
Figure 32. Error Flag Operation
The internal error flag comparators have open drain output stages. Hence, the ERROR pins should be pulled
high through a pull up resistor. Although the ERROR pin can sink current of 1mA, this current adds to the battery
drain. Hence, the value of the pull up resistor should be in the range of 100kΩ to 1MΩ. The ERROR pins must
be connected to ground if this function is not used. It should also be noted that when the shutdown pins are
pulled low, the ERROR pins are forced to be invalid for reasons of saving power in shutdown mode.
Shutdown Operation
The two LDO regulators in the LP2966 have independent shutdown. A CMOS Logic level signal at the shutdown
(SD) pin will turn-off the corresponding regulator. Pins SD1 and SD2 must be actively terminated through a
100kΩ pull-up resistor for a proper operation. If these pins are driven from a source that actively pulls high and
low (such as a CMOS rail to rail comparator), the pull-up resistor is not required. These pins must be tied to Vin if
not used.
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