PAM2320 Ver la hoja de datos (PDF) - Diodes Incorporated.

Número de pieza

componentes Descripción

Fabricante

PAM2320

3A LOW NOISE STEP-DOWN DC-DC CONVERTER

Diodes Incorporated. 

A Product Line of

Diodes Incorporated

PAM2320

Application Information (cont.)

For the condition where the step-down converter is in dropout at 100% duty cycle, the total device dissipation reduces to:

PD = IO 2 RDS(ON)H + IQ VIN

Since RDS(ON), quiescent current, and switching losses all vary with input voltage, the total losses should be investigated over the complete input

voltage range. The maximum power dissipation depends on the thermal resistance of IC package, PCB layout, the rate of surrounding airflow

and temperature difference between junction and ambient. The maximum power dissipation can be calculated by the following formula:

PD

=

TJ(MAX) − TA

θJA

Where TJ(max) is the maximum allowable junction temperature +125°C. TA is the ambient temperature and θJA is the thermal resistance from the

junction to the ambient. Based on the standard JEDEC for a two layers thermal test board, the thermal resistance θJA of SOP-8(EP) 90°C/W

respectively. The maximum power dissipation at TA = +25°C can be calculated by following formula:

PD = (125°C - 25°C) /90°C/W = 1.11W (SOP-8)

Setting the Output Voltage

The internal reference is 0.6V (Typical). The output voltage is calculated as below:

The output voltage is given by Table 1.

VO

=

0.6x⎜⎛1 +

⎝

R1

R2

⎟⎞

⎠

Table 1: Resistor selection for output voltage setting.

VO

1.2V

1.5V

1.8V

2.5V

3.3V

R1

150k

225k

300k

475k

680k

R2

150k

150k

150k

150k

150k

100% Duty Cycle Operation

As the input voltage approaches the output voltage, the converter turns the P-Channel transistor continuously on. In this mode the output voltage

is equal to the input voltage minus the voltage drop across the P-Channel transistor:

( ) VOUT = VIN − ILOAD RDSON + RL

where RDS(ON) = P-Channel switch ON resistance, ILOAD = Output Current, RL = Inductor DC Resistance

UVLO and Soft-Start

The reference and the circuit remain reset until the VIN crosses its UVLO threshold.

The PAM2320 has an internal soft-start circuit that limits the in-rush current during start-up. This prevents possible voltage drops of the input

voltage and eliminates the output voltage overshoot. The soft-start make the output voltage rise up smoothly.

Short Circuit Protection

The switch peak current is limited cycle-by-cycle to a typical value of 4A. In the event of an output voltage short circuit, the device operates with

a frequency of 500kHz and minimum duty cycle, therefore the average input current is more smaller than current limit.

Thermal Shutdown

When the die temperature exceeds +150°C, a reset occurs and the reset remains until the temperature decrease to +120°C, at which time the

circuit can be restarted.

PAM2320

Document number: DSxxxxx Rev. 1 - 0

9 of 12

www.diodes.com

October 2012

© Diodes Incorporated

Share Link: