0

0.02

0.04

0.06

0.08

0.10

0.12

0.14

9

10

11

12

13

14

15

Vo1 − Output Voltage − V

Vo3 = 18 V (Doubler Mode)

0

0.02

0.04

0.06

0.08

0.10

0.12

9

10

11

12

13

14

15

Vo1 − Output Voltage − V

Vo3 = 28 V (Tripler Mode)

DETAILED DESCRIPTION

Main Boost Converter

Power-Good Output

Enable and Power-On Sequencing (EN, ENR)

TPS65140-Q1

TPS65145-Q1

Vo3 MAXIMUM LOAD CURRENT

Vo3 MAXIMUM LOAD CURRENT

Figure 13.

Figure 14.

The TPS65140/45 consists of a main boost converter operating with a fixed switching frequency of 1.6 MHz to

allow for small external components. The boost converter output voltage Vo1 is also the input voltage, connected

via the pin SUP, for the positive and negative charge pump. The linear regulator controller is independent from

this system with its own enable pin. This allows the linear regulator controller to continue to operate while the

other supply rails are disabled or in shutdown due to a fault condition on one of their outputs. Refer to the

functional block diagram for more information.

The main boost converter operates with PWM and a fixed switching frequency of 1.6 MHz. The converter uses a

unique fast response, voltage mode controller scheme with input voltage feedforward. This achieves excellent

line and load regulation (0.2% A load regulation typical) and allows the use of small external components. To add

higher flexibility to the selection of external component values, the device uses external loop compensation.

Although the boost converter looks like a nonsynchronous boost converter topology operating in discontinuous

mode at light load, the TPS65140/45 maintains continuous conduction even at light load currents.

This is achieved with a novel architecture using an external Schottky diode and an integrated MOSFET in parallel

connected between SW and SUP (see the functional block diagram). The integrated MOSFET Q2 allows the

inductor current to become negative at light load conditions. For this purpose, a small integrated P-channel

MOSFET with typically 10

with the lower forward voltage conducts the current. This causes the converter to operate with a fixed frequency

in continuous conduction mode over the entire load current range. This avoids the ringing on the switch pin as

seen with a standard nonsynchronous boost converter and allows a simpler compensation for the boost

converter.

The TPS65140/45 has an open-drain power-good output with a maximum sink capability of 1 mA. The

power-good output goes high as soon as the main boost converter Vo1 and the negative and the positive charge

pumps are within regulation. The power-good output goes low as soon as one of the outputs is out of regulation.

In this case, the device goes into shutdown at the same time. See the electrical characteristics table for the

power-good thresholds.

The device has two enable pins. These pins should be terminated and not left floating to prevent faulty operation.

Pulling the enable pin (EN) high enables the device and starts the power-on sequencing with the main boost

converter Vo1 coming up first, then the negative and positive charge pumps. The linear regulator has an

independent enable pin (ENR). Pulling this pin low disables the regulator, and pulling this pin high enables this

regulator.

10

Submit Documentation Feedback

Copyright © 2004–2008, Texas Instruments Incorporated

Product Folder Link(s): TPS65140-Q1 TPS65145-Q1