TEA1738T Ver la hoja de datos (PDF) - NXP Semiconductors.

Número de pieza

componentes Descripción

Fabricante

TEA1738T

GreenChip SMPS control IC

NXP Semiconductors. 

NXP Semiconductors

TEA1738T; TEA1738LT

GreenChip SMPS control IC

2

1.7

IISENSE

(μA)

0.68 1

Fig 9. Overpower compensation

2

3

4

VVINSENSE (V)

014aaa933

7.12 Soft start-up (ISENSE pin)

A soft start is performed to prevent audible noise during start-up or a restart condition.

Before the converter (re)starts, soft start capacitor C6 (see Figure 3) on the ISENSE pin is

charged. When the converter (re)starts switching, the primary peak current slowly

increases as the soft start capacitor discharges through the soft start resistor (R6, see

Figure 3).

The soft start time constant is set by the soft start capacitor value chosen. The soft start

resistor value must also be taken into account, but this value is typically defined by the

overpower compensation (see Section 7.11).

7.13 Peak power, medium power and low power operation

The switching frequency is increased for peak power operation. In medium power

operation the switching losses are reduced by lowering the switching frequency. A second

frequency reduction step is made when the output power is reduced to low power. In low

power operation the converter switching frequency is reduced while the peak current is

set to 25 % of the maximum peak current (see Figure 7 and Figure 10).

fosc

80 kHz

66 kHz

28 kHz

high

power

peak power

medium

power

low power

1

Fig 10. Frequency control

2

3

VCTRL

014aab294

TEA1738T_TEA1738LT

Product data sheet

All information provided in this document is subject to legal disclaimers.

Rev. 2 — 14 January 2011

© NXP B.V. 2011. All rights reserved.

10 of 21

Share Link: