LD1117V33 Voltage Regulator 3.3V / 800mA

Description

The LD1117V33 is a low drop-out linear regulator that outputs 3.3V at up to 800mA with an input voltage can range of 4.5 – 15V.

PACKAGE INCLUDES:

• LD1117V33 Voltage Regulator

KEY FEATURES OF LD1117V33 VOLTAGE REGULATOR:

• Fixed voltage LDO (low drop-out) linear regulator
• 4.5-15V input voltage range
• 3.3V fixed output voltage
• 800mA continuous current with 1.3A surge capability
• TO-220 package

The LD1117Vxx series of LDO fixed-voltage linear regulators are some of the more popular LDO linear regulators available.

Since they are LDO (Low Drop-Out), they do not drop as much voltage across the device as the more common regulators such as the 78xx series do.  The LD1117V33 drops just 1V which allows it to run from a 4.5V supply which is handy since these are often used with 5V power systems to drop the 5V down to 3.3V.  They have built-in current limiting and over temperature protection and tend to be fairly robust devices.

Basic Operation

The LD1117V33 is perhaps the most commonly used LDO linear regulator available.  Input voltage can range from 4.5 – 15VDC and it outputs a fixed 3.3V at 800mA of current and up to 1.3A of surge current.

For basic operation, a 0.1uF bypass cap is recommended on the input and a 10uF or larger electrolytic cap on the output as shown below.

Power Dissipation

Linear regulators have less ripple on their outputs compared to DC-DC converters that can be used for the same basic purpose, but the trade-off is that the linear regulators also tend to dissipate more heat in the process.  The reason is that the linear regulator uses a series pass transistor on its output to drop the excess voltage.

The power dissipation of a linear regulator is dependent on the difference between the input voltage (Vin) and the output voltage (Vout) along with the amount of current that is being drawn from the regulator.  The larger the voltage difference is between Vin and Vout, the higher the power dissipation will be which limits how much current can be drawn from the device.

The power dissipation of the LD1117V33 device is easily calculated as Power Dissipation = (Vin – Vout) * Iout.

If the LD1117V33 input is 5V and it is providing 800mA of current, then Power Dissipation = (5V – 3.3V) * 0.8A = 1.36W.  The LD1117V33 TO-220 package will need to dissipate 1.36W of power.  Under typical conditions, the device can dissipate about 1 – 1.25W before a heat sink becomes necessary, so in our example here, the device would benefit from a heat sink. The maximum output current to safely run without a heat sink in this case would be limited to about 650mA and the device will be running in the range of 90°C.

As a general rule, you always want to use as low of an input voltage as possible to minimize power loss though the device and maximize the output current available.

Notes: 

1. The tab of the LD1117V33 is common with the Vout pin.
2. Under high current loads or with large input to output voltage differentials, the device can get very hot, so use care when handling.

Technical Specifications