TC1016_13 Datasheet, PDF (9/22 Pages) Microchip Technology – 80 mA, Tiny CMOS LDO With Shutdown

4.0 DETAILED DESCRIPTION
The TC1016 is a precision, fixed-output, linear voltage
regulator. The internal linear pass element is a P-
channel MOSFET. As with all P-channel CMOS LDOs,
there is a body drain diode, with the cathode connected
to V_IN and the anode connected to V_OUT (Figure 4-1).
As shown in Figure 4-1, the output voltage of the LDO
is sensed and divided down internally to reduce
external component count. The internal error amplifier
has a fixed, band gap reference on the inverting input,
with the sensed output voltage on the non-inverting
input. The error amplifier output will pull the gate
voltage down until the inputs of the error amplifier are
equal in order to regulate the output voltage.
By sensing the current in the P-channel MOSFET, the
maximum current delivered to the load is limited to a
typical value of 120 mA, preventing excessive current
from damaging the Printed Circuit Board (PCB) in the
event of a shorted or faulted load.
An internal thermal sensing device is used to monitor
the junction temperature of the LDO. When the sensed
temperature is over the set threshold of 160°C (typ.),
the P-channel MOSFET is turned off. When the
MOSFET is off, the power dissipation internal to the
device is almost zero. The device cools until the
junction temperature is approximately 150°C and the
TC1016
MOSFET is turned on. If the internal power dissipation
is still high enough for the junction to rise to 160°C, it
will again shut off and cool. The maximum operating
junction temperature of the device is 125°C. Steady-
state operation at or near the 160°C overtemperature
point can lead to permanent damage of the device.
The output voltage (V_OUT) remains stable over the
entire input operating voltage range (2.7V to 6.0V), as
well as the entire load range (0 mA to 80 mA). The
output voltage is sensed through an internal resistor
divider and compared with a precision internal voltage
reference. Several fixed-output voltages are available
by changing the value of the internal resistor divider.
Figure 4-2 shows a typical application circuit. The reg-
ulator is enabled anytime the shutdown input pin is at
or above V_IH, and shutdown (disabled) anytime the
shutdown input pin is below V_IL. For applications where
the SHDN feature is not used, tie the SHDN pin directly
to the input supply voltage source. While in shutdown,
the supply current decreases to 0.05 µA (typ.) and the
P-channel MOSFET is turned off.
As shown in Figure 4-2, batteries have internal source
impedance. An input capacitor in used to lower the
input impedance of the LDO. In some applications, high
input impedance can cause the LDO to become
unstable. Adding more input capacitance can
compensate for this.
FIGURE 4-1:
1 SHDN
2 NC
3 GND
V_IN
SHDN V_REF
Control
Over
Temp.
Current Limit
V_{IN 5}
+-EA
Body
Diode
Error Amp
R₁ R₂
Feedback Resistors
V_{OUT 4}
TC1016 Block Diagram.
FIGURE 4-2:
R_SOURCE
1 _SHDN
V_IN ⁵
TC1016
2 _NC
C_IN
1 µF Ceramic
3 _GND
V_OUT ⁴
C_OUT
Load
1 µF Ceramic
Typical Application Circuit.
© 2005 Microchip Technology Inc.
DS21666B-page 9