參數(shù)資料
型號(hào): TPS40074RHLRG4
廠商: TEXAS INSTRUMENTS INC
元件分類: 穩(wěn)壓器
英文描述: 2 A SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PQCC20
封裝: GREEN, PLASTIC, QFN-20
文件頁數(shù): 11/41頁
文件大?。?/td> 765K
代理商: TPS40074RHLRG4
www.ti.com
TPS40074 POWER DISSIPATION
P
D + Qg
V
DR
f
SW
(Watts driver)
(14)
P
T +
2
P
D
V
DR
) IQ
V
IN
(Watts)
(15)
P
T + 2
Qg
f
SW ) IQ
V
IN
(Watts)
(16)
P
T +
T
J * TA
qJA
(Watts)
(17)
f
SW +
T
J*TA
qJA VIN
* IQ
2
Qg
(Hz)
(18)
BOOST DIODE
LOW VOLTAGE OPERATION
SLUS617B – APRIL 2005 – REVISED OCTOBER 2006
APPLICATION INFORMATION (continued)
The power dissipation in the TPS40074 is largely dependent on the MOSFET driver currents and the input
voltage. The driver current is proportional to the total gate charge, Qg, of the external MOSFETs. Driver power
(neglecting external gate resistance) can be calculated from:
where
V
DR is the driver output voltage
The total power dissipation in the TPS40074, assuming the same MOSFET is selected for both the high-side
and synchronous rectifier is described in Equation 15.
or
where
I
Q is the quiescent operating current (neglecting drivers)
The maximum power capability of the TPS40074 PowerPAD package is dependent on the layout as well as air
flow. The thermal impedance from junction to air ambient assuming 2-oz. copper trace and thermal pad with
solder and no air flow is
θ
JA = 60 °C/W
The maximum allowable package power dissipation is related to ambient temperature by Equation 17.
Substituting Equation 17 into Equation 16 and solving for fSW yields the maximum operating frequency for the
TPS4007x. The result is described in Equation 18.
The TPS40074 has internal diodes to charge the boost capacitor connected from SW to BOOST. The drop
across this diode is rather large at 1.4-V nominal at room temperature resulting in the drive voltage to the
high-side MOSFET being reduced by this amount from the DBP voltage. If this drop is too large for a particular
application, an external diode may be connected from DBP (anode) to BOOST (cathode). This provides
significantly improved gate drive for the high-side MOSFET, especially at lower input voltages.
If the programmable UVLO is set to less than 6.5 V nominal, connect a 330-k
resistor across the soft-start
capacitor. This eliminates a race condition inside the device that can lead to an output voltage overshoot on
power down of the part.
19
相關(guān)PDF資料
PDF描述
TPS40074RHL 2 A SWITCHING CONTROLLER, 550 kHz SWITCHING FREQ-MAX, PQCC20
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