LP3964EMP-3.3 National Semiconductor, LP3964EMP-3.3 Datasheet - Page 14

• Manufacturer Part Number: LP3964EMP-3.3
• Description: Linear Voltage Regulator IC
• Manufacturer: National Semiconductor

Specifications of LP3964EMP-3.3

• No. Of Pins: 5
• Output Current: 0.8A
• Peak Reflow Compatible (260 C): No
• Current Rating: 800A
• Output Voltage Max: 3.3V
• Leaded Process Compatible: No
• Mounting Type: Surface Mount
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

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Application Hints
Once the power pass element shuts down, the control loop
will rapidly cycle the output on and off until the average
power dissipation causes the thermal shutdown circuit to
respond to servo the on/off cycling to a lower frequency.
Please refer to the section on thermal information for power
dissipation calculations.
ERROR FLAG OPERATION
The LP3961/LP3964 produces a logic low signal at the Error
Flag pin when the 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 1
SENSE PIN
In applications where the regulator output is not very close to
the load, LP3964 can provide better remote load regulation
using the SENSE pin. Figure 2 depicts the advantage of the
SENSE option. LP3961 regulates the voltage at the output
pin. Hence, the voltage at the remote load will be the regu-
lator output voltage minus the drop across the trace resis-
(Continued)
FIGURE 1. Error Flag Operation
14
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.
The internal Error flag comparator has an open drain output
stage. Hence, the ERROR pin should be pulled high through
a pull up resistor. Although the ERROR pin can sink current
of 1mA, this current is energy drain from the input supply.
Hence, the value of the pull up resistor should be in the
range of 100kΩ to 1MΩ. The ERROR pin must be con-
nected to ground if this function is not used. It should
also be noted that when the shutdown pin is pulled low, the
ERROR pin is forced to be invalid for reasons of saving
power in shutdown mode.
tance. For example, in the case of a 3.3V output, if the trace
resistance is 100mΩ, the voltage at the remote load will be
3.22V with 800mAmps of load current, I
regulates the voltage at the sense pin. Connecting the sense
pin to the remote load will provide regulation at the remote
load, as shown in Figure 2. If the sense option pin is not
required, the sense pin must be connected to the V
10112907
LOAD
. The LP3964
OUT
pin.