8 Detailed Description

8.1 Overview

The TPS60400, TPS60401 charge pumps invert the voltage applied to their input. For the highest performance,

use low equivalent series resistance (ESR) capacitors (for example, ceramic). During the first half-cycle,

switches S2 and S4 open, switches S1 and S3 close, and capacitor (C(fly)) charges to the voltage at VI. During

the second half-cycle, S1 and S3 open, S2 and S4 close. This connects the positive terminal of C(fly) to GND and

the negative to VO. By connecting C(fly) in parallel, CO is charged negative. The actual voltage at the output is

more positive than -VI, since switches S1-S4 have resistance and the load drains charge from CO.

C(fly)

1 µF

S2

S1

S3

S4

CO

1 µF

VO (–VI)

GND

VI

GND

Figure 8-1. Operating Principle

8.2 Functional Block Diagram

Start

FF

R

S

Q

VI – VCFLY+ < 0.5 V

VI

MEAS

VI < 1 V

VI

VO > Vbe

VO

MEAS

VO

OSC

OSC

CHG

50 kHz

VO > –1 V

VI / VO

MEAS

VI

VO

VCO_CONT

VO < –VI – Vbe

Phase

Generator

DC_ Startup

C(fly)

+

Q3

Q2

Q1

Q4

VI

VO

GND

Q5

Q

Q

B

DC_ Startup

TPS60400, TPS60401, TPS60402, TPS60403

SLVS324C – JULY 2001 – REVISED OCTOBER 2020

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