TD1410 データシートの表示（PDF） - Unspecified

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TD1410

1.8A 380KHZ 20V PWM Buck DC/DC Converter

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Datasheet

1.8A 380KHZ 20V PWM Buck DC/DC Converter

TD1410C

This capacitor type can be ceramic, plastic, silver

mica, etc.(Because of the unstable characteristics

of ceramic capacitors made with Z5U material,

they are not recommended.)

Note:In PCB layout. Reserved an area for CFF.

Over Current Protection (OCP)

The cycle by cycle current limit threshold is set

between 3A and 4A. When the load current

reaches the current limit threshold, the cycle by

cycle current limit circuit turns off the high side

switch immediately to terminate the current duty

cycle. The inductor current stops rising. The cycle

by cycle current limit protection directly limits

inductor peak current. The average inductor

current is also limited due to the limitation on peak

inductor current. When the cycle by cycle current

limit circuit is triggered, the output voltage drops

as the duty cycle is decreasing.

Thermal Management and Layout

Consideration

In the TD1410C buck regulator circuit, high

pulsing current flows through two circuit loops.

The first loop starts from the input capacitors, to

the VIN pin, to the VOUT pins, to the filter

inductor, to the output capacitor and load, and

then returns to the input capacitor through

ground.

Current flows in the first loop when the high side

switch is on. The second loop starts from the

inductor, to the output capacitors and load, to the

GND pin of the TD1410C, and to the VOUT pins

of the TD1410C. Current flows in the second loop

when the low side diode is on.

In PCB layout, minimizing the two loops area

reduces the noise of this circuit and improves

efficiency. A ground plane is recommended to

connect input capacitor, output capacitor, and

GND pin of the TD1410C.

In the TD1410C buck regulator circuit, the two

major power dissipating components are the

TD1410C and output inductor. The total power

dissipation of converter circuit can be measured

by input power minus output power.

Ptotal _loss = V IN × IIN – V O × IO

The power dissipation of inductor can be

approximately calculated by output current and

DCR of inductor.

Pinductor _loss= IO 2 × Rinductor × 1.1

The junction to ambient temperature can be got

from power dissipation in the TD1410C and

thermal impedance from junction to ambient.

T (jun-amb) =(Ptotalloss–Pinductorloss)× ΘJA

The maximum junction temperature of TD1410C

is 145°C, which limits the maximum load current

capability. Please see the thermal de-rating

curves for the maximum load current of the

TD1410C under different ambient temperatures.

The thermal performance of the TD1410C is

trongly

affected by the PCB layout. Extra care should be

taken by users during the design process to nsure

that the IC will operate under the recommended

environmental conditions.

Several layout tips are listed below for the best

electric and thermal performance.

1. Do not use thermal relief connection to the VIN

and the GND pin. Pour a maximized copper area

to the GND pin and the VIN pin to help thermal

dissipation.

2. Input capacitor should be connected to the VIN

pin and the GND pin as close as possible.

3. Make the current trace from VOUT pins to L to

the GND as short as possible.

4. Pour copper plane on all unused board area

and connect it to stable DC nodes, like VIN, GND,

or VOUT.

5. Keep sensitive signal traces such as trace

connecting FB pin away from the VOUT pins.

February, 2007 Rev 2.0

Techcode Semiconductor Limited

11

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