LT3469 Ver la hoja de datos (PDF) - Linear Technology
Número de pieza
componentes Descripción
Fabricante
LT3469 Datasheet PDF : 8 Pages
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U
OPERATIO
as short as possible. To prevent electromagnetic interfer-
ence (EMI) problems, proper layout of the high frequency
switching path is essential. The voltage signal of the SW
pin has sharp rise and fall edges. The SW pin should be
surrounded on three sides by metal connected to VCC to
shield +IN and –IN. Minimize the area of all traces con-
nected to the SW pin and always use a ground plane under
the switching regulator to minimize interplane coupling. In
addition, the ground connection for the feedback resistor
R1 should be tied directly to the GND pin and not shared
with any other component, ensuring a clean, noise-free
connection. The ground return of the piezoceramic
microactuator should also have a direct and unshared
connection to the GND pin. The GND connection to R5
should be tied directly to the ground of the source gener-
ating the INPUT signal to avoid error induced by voltage
drops along the GND line. Recommended component
placement is shown in Figure 6.
Thermal Considerations and Power Dissipation
The LT3469 combines large output drive with a small
package. Because of the high supply voltage capability, it
is possible to operate the part under conditions that
exceed the maximum junction temperature. Maximum
junction temperature (TJ) is calculated from the ambient
temperature (TA) and power dissipation (PD) as follows:
TJ = TA + (PD • 250°C/W)
Worst-case power dissipation occurs at maximum output
swing, frequency, capacitance and VCC. For a square wave
LT3469
input, power dissipation is calculated from the amplifier
quiescent current (IQ), input frequency (f), output swing
(VOUT(P-P)), capacitive load (CL), amplifier supply voltage
(VCC) and switching regulator efficiency (η) as follows:
( )( ) PD =
IQ + fVOUT(P-P)CL
η
VCC
Example: LT3469 at TA = 70°C, VCC = 35V, CL = 200nF,
f = 3kHz, VOUT(P-P) = 4V, η = 80%:
PD
=
(2.5mA
+
3kHz • 4V
0.80
•
200nF)(35V)
=
214mW
TJ = 70°C + (214mW • 250°C / W ) = 124°C
Do not exceed the maximum junction temperature of
125°C.
GND INPUT
R3
R5 R4
PIEZ0
ACTUATOR
R1
R2
C1
VIN
VIAS TO GROUND PLANE
C2
L
3469 F06
Figure 6. Recommended Component Placement
TYPICAL APPLICATIO
Piezo Speaker Driver
VIN
3V TO 6V
L1
47µH
C1
3
5
1µF
VIN
SW
VCC 6
16.9k
+
INPUT
0V TO 3V
– 20k
7
+IN
8
–IN
LT3469
+
–
2
FB
4
GND
1
OUT
113k
C1, C2: X5R OR X7R DIELECTRIC
L1: MURATA LQH32CN470
SOUND PRESSURE LEVEL: 87dB AT 750Hz/10VP-P/10cm
WITH A 55nF PIEZO SPEAKER. IVIN WITH VIN = 3.3V:
24mA AT 750Hz/10VP-P WITH A 55nF PIEZO SPEAKER
294k
17.4k
C2
0.47µF
35V
VOUT
1V TO 20V
PIEZO
SPEAKER
8nF < C < 300nF
3469 TA01
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
3469f
7
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