米6体育平台手机版

ZHCSBQ2A April 2014 – May 2014 TPS62095

PRODUCTION DATA.

封装选项

机械数据 (封装 | 引脚)

RGT|16
- MPQF119H

散热焊盘机械数据 (封装 | 引脚)

RGT|16
- QFND098S

订购信息

8 Application and Implementation

8.1 Application Information

The TPS62095 is a synchronous step down converter based on DCS-Control™ topology whose output voltage can be adjusted by component selection. The following section discusses the design of the external components to complete the power supply design for several input and output voltage options by using typical applications as a reference.

8.2 Typical Applications

8.2.1 2.5V to 5.5V Input, 1.8V Output Converter

Figure 7. 1.8-V Output Application

8.2.1.1 Design Requirements

For this design example, use the following as the input parameters.

Table 1. Design Parameters

DESIGN PARAMETER	EXAMPLE VALUE
Input voltage range	2.5V to 5.5V
Output voltage	1.8V
Output ripple voltage	<20mV
Output current rating	4A

8.2.1.2 Detailed Design Procedure

8.2.1.2.1 Output Filter

The first step is the selection of the output filter components. To simplify this process, Table 2 outlines possible inductor and capacitor value combinations.

Table 2. Output Filter Selection

INDUCTOR VALUE [µH]⁽³⁾	OUTPUT CAPACITOR VALUE [µF]⁽²⁾
INDUCTOR VALUE [µH]⁽³⁾	10	22	2 x 22	100	150
0.47			√	√	√
1.0			√⁽¹⁾	√	√
2.2

(1) Typical application configuration. Other check mark indicates alternative filter combinations

(2) Capacitance tolerance and bias voltage de-rating is anticipated. The effective capacitance can vary by +20% and –50%.

(3) Inductor tolerance and current de-rating is anticipated. The effective inductance can vary by +20% and –30%.

8.2.1.2.2 Inductor Selection

The inductor selection is affected by several parameters like inductor ripple current, output voltage ripple, transition point into Power Save Mode, and efficiency. See Table 3 for typical inductors.

Table 3. Inductor Selection⁽¹⁾

INDUCTOR VALUE	COMPONENT SUPPLIER	SIZE (LxWxH mm)	Isat / DCR
1 µH	Coilcraft XAL4020-102	4.0 x 4.0 x 2.1	8.75A / 13.2 mΩ
0.47 µH	TOKO DFE322512C	3.2 x 2.5 x 1.2	5.9A / 21 mΩ

(1) See Third-Party Products Disclaimer.

In addition, the inductor has to be rated for the appropriate saturation current and DC resistance (DCR). The inductor needs to be rated for a saturation current as high as the typical switch current limit of 5.5A or according to Equation 6 and Equation 7. Equation 6 and Equation 7 calculate the maximum inductor current under static load conditions. The formula takes the converter efficiency into account. The converter efficiency can be taken from the data sheet graphs or 80% can be used as a conservative approach. The calculation must be done for the maximum input voltage where the peak switch current is highest.

Equation 6.

Equation 7.

where

ƒ = Converter switching frequency (typically 1.4MHz)
L = Inductor value
η = Estimated converter efficiency (use the number from the efficiency curves or 0.80 as a conservative assumption)

Note: The calculation must be done for the maximum input voltage of the application

Calculating the maximum inductor current using the actual operating conditions gives the minimum saturation current. A margin of 20% should be added to cover for load transients during operation.

8.2.1.2.3 Input and Output Capacitor Selection

For best output and input voltage filtering, low ESR ceramic capacitors are recommended. The input capacitor minimizes input voltage ripple, suppresses input voltage spikes and provides a stable system rail for the device. A 22µF or larger input capacitor is required. The output capacitor value can range from 2x22µF up to 150µF. The recommended typical output capacitor value is 2x22µF and can vary over a wide range as outline in the output filter selection table.

8.2.1.2.4 Setting the Output Voltage

The output voltage is set by an external resistor divider according to the following equations:

Equation 8.

Equation 9.

Equation 10.

When sizing R2, in order to achieve low quiescent current and acceptable noise sensitivity, use a minimum of 5µA for the feedback current I_FB. Larger currents through R2 improve noise sensitivity and output voltage accuracy.