TD1509 查看數據表（PDF） - Unspecified
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TD1509 Datasheet PDF : 17 Pages
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Techcode®
2A 150KHz PWM Buck DC/DC Converter
Function Description(Cont.)
DATASHEET
TD1509
noise of this circuit and improves efficiency. A ground
plane is recommended to connect input capacitor, output
capacitor, and GND pin of the TD1509.
In the TD1509 buck regulator circuit, the two major
power dissipating components are the TD1509 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 TD1509 and thermal impedance
from junction to ambient.
T (jun-amb) =(Ptotalloss–Pinductorloss)× ΘJA
The maximum junction temperature of TD1509 is 145°C,
which limits the maximum load current capability. Please
see the thermal de-rating curves for the maximum load
current of the TD1509 under different ambient
temperatures.
The thermal performance of the TD1509 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.
December, 20, 2005.
Techcode Semiconductor Limited
14
www.techcodesemi.com
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