TC682 datasheet(6/14 Pages) MICROCHIP

6 / 14 page

TC682

DS21453C-page 6

4.3

Paralleling Devices

Paralleling

multiple

TC682s

reduces

the

output

resistance of the converter. The effective output

resistance is the output resistance of a single device

divided by the number of devices. As illustrated in

Figure , each requires separate pump capacitors C1

and C2, but all can share a single reservoir capacitor.

4.4

-5V Regulated Supply From A

Single 3V Battery

Figure 4-3 shows a -5V power supply using one 3V

battery. The TC682 provides -6V at VOUT, which is

regulated to -5V by the negative LDO. The input to the

TC682 can vary from 3V to 5.5V without affecting

regulation appreciably. A TC54 device is connected to

the battery to detect undervoltage. This unit is set to

detect at 2.7V. With higher input voltage, more current

can be drawn from the outputs of the TC682. With 5V

at VIN, 10 mA can be drawn from the regulated output.

Assuming 150

Ω source resistance for the converter,

with IL

–= 10 mA, the charge pump will droop 1.5V.

FIGURE 4-2:

Paralleling TC682 for Lower Output Source Resistance

FIGURE 4-3:

Negative Supply Derived from 3V Battery

μF

VIN

GND

Negative

Supply

TC682

GND

–

VIN

C1+

C2+

C1–

C2–

V–OUT

VIN

C1+

C2+

C1–

C2–

V–OUT

C–OUT

VSS

GND

TC682

Ground

-5 Supply

LOW BATTERY

Negative LDO

Regulator

TC54VC2702Exx

μF

–

μF

VIN

C1+

C2+

C1–

C2–

VIN

VOUT

V–OUT

COUT–

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