 2002-2012 Microchip Technology Inc.

DS21364C-page 7

TC1188/TC1189

FIGURE 3-2:

Functional Block Diagram.

3.4

Shutdown

The SHDN input is used to turn off the LDO P-Channel

pass MOSFET and internal bias. When shutdown, the

typical quiescent current consumed by the LDO is

0.1 nA. A logic low (< 0.4V) at the SHDN input will

cause the device to operate in the shutdown mode. A

logic high (> 2.0V) at the SHDN input will cause the

device to operate in the normal mode.

3.5

Current Limit

The LDO output current is monitored internal to the

TC1188/TC1189. The internal current sense will limit

the LDO output current to a typical value of 280 mA.

The current limit can range from approximately 50 mA

to 410 mA from device to device. The internal current

limit protects the device from a continuous output short

circuit.

3.6

Thermal Overload Protection

Integrated thermal protection circuitry shuts the

TC1188/TC1189 off when the internal die temperature

exceeds approximately 170°C. The regulator output

remains off until the internal die temperature drops to

approximately 150°C.

3.7

Operating Region and Power

Dissipation

The internal power dissipation to the LDO is primarily

determined by the input voltage, output voltage and

output current. The following equation is used to

approximate the worst case for power dissipation:

EQUATION

The maximum power dissipation is a function of the

resistance from junction to air,

package has a

EQUATION

Bandgap

Reference

MOS Driver

Thermal

Sensor

Shutdown

Logic

Error

+

–

SHDN

GND

PMOS Pass

GND

N

(TC1189 Only)

Amplifier

Transistor

Where:

P

V

IN

V

OUT

I

LOAD

Where all terms are previously defined.