PIC12F609-ESLASHP datasheet(127/212 Pages) MICROCHIP

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 2010 Microchip Technology Inc.

DS41302D-page 127

PIC12F609/615/617/12HV609/615

13.0

VOLTAGE REGULATOR

The PIC12HV609/HV615 devices include a permanent

internal 5 volt (nominal) shunt regulator in parallel with

the VDD pin. This eliminates the need for an external

voltage

regulator

systems

sourced

unregulated supply. All external devices connected

directly to the VDD pin will share the regulated supply

voltage and contribute to the total VDD supply current

(ILOAD).

13.1

Regulator Operation

A shunt regulator generates a specific supply voltage

by creating a voltage drop across a pass resistor RSER.

The voltage at the VDD pin of the microcontroller is

monitored and compared to an internal voltage refer-

ence. The current through the resistor is then adjusted,

based on the result of the comparison, to produce a

voltage drop equal to the difference between the supply

voltage VUNREG and the VDD of the microcontroller.

See Figure 13-1 for voltage regulator schematic.

FIGURE 13-1:

VOLTAGE REGULATOR

An external current limiting resistor, RSER, located

between the unregulated supply, VUNREG, and the VDD

pin, drops the difference in voltage between VUNREG

and VDD. RSER must be between RMAX and RMIN as

defined by Equation 13-1.

EQUATION 13-1:

RSER LIMITING RESISTOR

13.2

Regulator Considerations

The supply voltage VUNREG and load current are not

constant. Therefore, the current range of the regulator

is limited. Selecting a value for RSER must take these

three factors into consideration.

Since the regulator uses the band gap voltage as the

regulated voltage reference, this voltage reference is

permanently enabled in the PIC12HV609/HV615

devices.

The shunt regulator will still consume current when

below operating voltage range for the shunt regulator.

13.3

Design Considerations

For more information on using the shunt regulator and

managing current load, see Application Note AN1035,

“Designing with HV Microcontrollers” (DS01035).

Feedback

VDD

VSS

CBYPASS

RSER

VUNREG

ISUPPLY

ISHUNT

ILOAD

Device

RMAX =

(VUMIN - 5V)

1.05 • (4 MA + ILOAD)

RMIN =

(VUMAX - 5V)

0.95 • (50 MA)

Where:

RMAX = maximum value of RSER (ohms)

RMIN

= minimum value of RSER (ohms)

VUMIN = minimum value of VUNREG

VUMAX = maximum value of VUNREG

VDD

= regulated voltage (5V nominal)

ILOAD = maximum expected load current in mA

including I/O pin currents and external

circuits connected to VDD.

1.05

= compensation for +5% tolerance of RSER

0.95

= compensation for -5% tolerance of RSER

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