SP6832 datasheet(8/15 Pages) SIPEX

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SP6832DS/04

SP6832 High Speed, High Efficiency Voltage Inverter

DESCRIPTION

The SP6832 is a CMOS Charge Pump Voltage

Converter that can be used to invert a +1.15V

to +5.3V input voltage. These devices are ideal

for designs involving battery-powered and/or

board level voltage conversion applications.

The typical operating frequency of the SP6832

is 500kHz. The SP6832 has a typical operating

current of 800

µA. The device can output 25mA

with a voltage drop of 500mV. The devices are

ideal for designs using +3.3V or +3.6V lithium

ion batteries such as cell phones, PDAs, medical

instruments, and other portable equipment.

The SP6832 combines a high efficiency with

a low quiescent current.

THEORY OF OPERATION

The SP6832 should theoretically produce an

inverted input voltage. In real world applications,

there are small voltage drops at the output that

reduce efficiency. The circuit of an ideal voltage

inverter can be found in Figure 16. The voltage

inverters require two external capacitors to

store the charge. A description of the two

phases follows:

Phase 1

In the first phase of the clock cycle, switches S1

and S3 are opened and S2 and S4 are closed.

This connects the flying capacitor, C1, from V

to ground. C1 charges up to the input voltage

applied at V

IN.

Phase 2

In the second phase of the clock cycle, switches

S1 and S3 are opened and S2 and S4 are closed.

This connects the flying capacitor, C1, in parallel

with the output capacitor, C2. The charge stored

in C1 is now transferred to C2. Simultaneously,

the negative side of C2 is connected to V

OUT and

the positive side is connected to ground. With

the voltage across C2 smaller than the voltage

across C1, the charge flows from C1 to C2 until

the voltage at the V

OUT equals -VIN.

Charge-Pump Output

The output of the SP6832 is not regulated and

therefore is dependent on the output resistance

and the amount of load current. As the load

current increases, losses may slightly increase

at the output and the voltage may become

slightly more positive. The loss at the negative

output, V

LOSS, equals the current draw, IOUT, from

OUT

times the negative converter's source

resistance, R

LOSS = IOUT x RS.

The actual inverted output voltage at V

OUT will

equal the inverted voltage difference of V

IN and

LOSS:

OUT = -(VIN - VLOSS).

Efficiency

Theoretically, the total power loss of a switched

capacitor voltage converter can be summed up as

follows:

∑P

LOSS = PINT + PCAP + PCONV,

where P

LOSS is the total power loss, PINT is the total

internal loss in the IC including any losses in the

MOSFET switches, P

CAP is the resistive loss of

Figure 16. Circuit for an Ideal Voltage Inverter

VOUT

VIN

VOUT = -VIN

SP6832 Datasheet(PDF) 8 Page - Sipex Corporation

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