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參數(shù)資料
| 型號： | REG1117-2.85 |
| 元件分類： | 固定正電壓單路輸出LDO穩(wěn)壓器 |
| 英文描述： | 2.85 V FIXED POSITIVE LDO REGULATOR, 1.2 V DROPOUT, PDSO4 |
| 封裝： | PLASTIC, SOT-223, 4 PIN |
| 文件頁數(shù)： | 8/10頁 |
| 文件大?。?/td> | 123K |
| 代理商： | REG1117-2.85 |
REG1117
7
THERMAL CONSIDERATIONS
The REG1117 has current limit and thermal shutdown
circuits that protect it from overload. The thermal shutdown
activates at approximately TJ = 165°C. For continuous op-
eration, however, the junction temperature should not be
allowed to exceed 125
°C. Any tendency to activate the
thermal shutdown in normal use is an indication of an
inadequate heat sink or excessive power dissipation. The
power dissipation is equal to:
PD = (VIN – VOUT) IOUT
The junction temperature can be calculated by:
TJ = TA + PD (θJA)
where TA is the ambient temperature, and
θ
JA is the junction-to-ambient thermal resistance
A simple experiment will determine whether the maximum
recommended junction temperature is exceeded in an actual
circuit board and mounting configuration: Increase the am-
bient temperature above that expected in normal operation
until the device’s thermal shutdown is activated. If this
occurs at more than 40
°C above the maximum expected
ambient temperature, then the TJ will be less than 125°C
during normal operation.
The internal protection circuitry of the REG1117 was de-
signed to protect against overload conditions. It was not
intended to replace proper heat sinking. Continuously run-
ning the REG1117 into thermal shutdown will degrade
reliability.
LAYOUT CONSIDERATIONS
The DDPAK (REG1117F-3.3 and REG1117FA) is a sur-
face-mount power package that has excellent thermal char-
acteristics. For best thermal performance, its mounting tab
should be soldered directly to a circuit board copper area
(see Figure 3). Increasing the copper area improves heat
dissipation. Figure 4 shows typical thermal resistance from
junction-to-ambient as a function of the copper area.
FIGURE 3. DDPAK Thermal Resistance vs Circuit Board Copper Area.
THERMAL RESISTANCE vs
CIRCUIT BOARD COPPER AREA
60
50
40
30
20
10
Thermal
Resistance,
θ
JA
(°C/W)
012345
Copper Area (inches2)
REG1117F
DDPAK Surface Mount Package
1oz copper
FIGURE 4. DDPAK Thermal Resistance vs Circuit Board Copper Area.
Circuit Board Copper Area
REG1117F
DDPAK Surface Mount Package
3-Lead DDPAK(1)
NOTE: (1) For improved thermal performance increase
footprint area. See Figure 4, “Thermal Resistance vs
Circuit Board Copper Area”.
All measurements
in inches.
0.45
0.085
0.2
0.51
0.10
0.155
0.05
相關PDF資料 |
PDF描述 |
|---|---|
| REG1117-3-TR | 3 V FIXED POSITIVE LDO REGULATOR, 1.2 V DROPOUT, PSSO3 |
| REG1117-2.85-TR | 2.85 V FIXED POSITIVE LDO REGULATOR, 1.2 V DROPOUT, PSSO3 |
| REG1117A-TR | ADJUSTABLE POSITIVE LDO REGULATOR, 1.55 V DROPOUT, PSSO3 |
| REG1117-3 | 3 V FIXED POSITIVE LDO REGULATOR, 1.2 V DROPOUT, PSSO3 |
| REG1117-3-TR | 3 V FIXED POSITIVE LDO REGULATOR, 1.2 V DROPOUT, PDSO4 |
相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| REG11172K5 | 制造商:TI 功能描述:New |
| REG1117-2K5 | 制造商:BB 制造商全稱:BB 功能描述:800mA and 1A Low Dropout Positive Regulator 1.8V, 2.5V, 2.85, 3.3V, 5V, and Adjustable |
| REG11172K5G4 | 制造商:BB 制造商全稱:BB 功能描述:800mA and 1A Low Dropout Positive Regulator 1.8V, 2.5V, 2.85, 3.3V, 5V, and Adjustable |
| REG1117-2K5G4 | 制造商:BB 制造商全稱:BB 功能描述:800mA and 1A Low Dropout Positive Regulator 1.8V, 2.5V, 2.85, 3.3V, 5V, and Adjustable |
| REG1117-3.3 | 功能描述:低壓差穩(wěn)壓器 - LDO 800mA & 1A LDO RoHS:否 制造商:Texas Instruments 最大輸入電壓:36 V 輸出電壓:1.4 V to 20.5 V 回動電壓（最大值）:307 mV 輸出電流:1 A 負載調節(jié):0.3 % 輸出端數(shù)量: 輸出類型:Fixed 最大工作溫度:+ 125 C 安裝風格:SMD/SMT 封裝 / 箱體:VQFN-20 |
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