GM6155 Просмотр технического описания (PDF) - Gamma Microelectronics Inc.
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GM6155 Datasheet PDF : 9 Pages
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Parameter
SOT-23-5
RqJA Recommended
Minimum Footprint
220°C/ W
RqJA 1" Square
Copper Clad
170°C/ W
Table 1. SOT-25 Thermal Resistance
RqJC
130°C/ W
The actual power dissipation of the regulator circuit can be determined by using the equation:
PD = (VIN - VOUT) IOUT + VIN IGND
Substituting PD(max) for PD and solving for the operating conditions that are critical to the application will give
the maximum operating conditions for the regulator circuit. For example, when operating Gm6155 at room
temperature with a minimum footprint layout, the maximum input voltage for a set output current can be
determined as follows:
PD(max)
=
(125°C - 25°C)
220°C/W
PD(max) = 455mW
The junction-to-ambient thermal resistance for the minimum footprint is 220°C/ W, from Table 1. The maximum
power dissipation must not be exceeded for proper operation. Using the output voltage of 3.3V and an output
current of 150mA, the maximum input voltage can be determined. From the Electrical Characteristics table, the
maximum ground current for150mA output current is 2500µA or 2.5mA.
455mW = (VIN - 3.3V) 150mA + VIN • 2.5mA
455mW = VIN • 150mA - 495mA + VIN • 2.5mA
950mW = VIN • 152.5mA
VIN(max) = 6.23V
Therefore, a 3.3V application at 150mA of output current can accept a maximum input voltage of 6.2V in a
SOT-25 package. For a full discussion of heat sinking and thermal effects on voltage regulators.
Fixed Regulator Applications
Figure 3. Ultra-Low-Noise Fixed Voltage Application
VIN
1
2
VOUT
5
2.2µF
3
4
470pF
Figure 4. Low-Noise Fixed Voltage Application
VIN
1
2
Enable
Shutdown
3
EN
VOUT
5
1.0µF
4
Figure 3. includes a 470pF capacitor for low-noise
operation and shows EN (pin 3) connected to IN (pin 1)
for an application where enable/ shutdown is not
required. COUT = 2.2µF minimum.
Figure 4. is an example of a low-noise configuration
where CBYP is not required. COUT = 1µF minimum.
Adjustable Regulator Applications
The GM6155 can be adjusted to a specific output voltage by using two externa resistors (Figure 5). The resistors set the
output voltage based on the following equation:
R2
VOUT = 1.242V X ( R1 +1)
6
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