 |
数据搜索系统，热门电子元器件搜索 |
|
|
数据搜索系统，热门电子元器件搜索 |
|
LT1940 数据表(PDF) 19 Page - Linear Technology |
|
||||||||||||||||||||||||||||||
LT1940 数据表(HTML) 19 Page - Linear Technology |
|
|
19 / 28 page  19 LT1766/LT1766-5 1766fa Thermal resistance for the LT1766 packages is influenced by the presence of internal or backside planes. SSOP (GN16) Package: With a full plane under the GN16 package, thermal resistance will be about 85 °C/W. TSSOP (Exposed Pad) Package: With a full plane under the TSSOP package, thermal resistance will be about 45 °C/W. To calculate die temperature, use the proper thermal resistance number for the desired package and add in worst-case ambient temperature: TJ = TA + (θJA • PTOT) When estimating ambient, remember the nearby catch diode and inductor will also be dissipating power: P VV V I V DIODE F IN OUT LOAD IN = ( )( – )( ) VF = Forward voltage of diode (assume 0.63V at 1A) PW DIODE == (. )( – )( ) . 063 40 5 1 40 055 PINDUCTOR = (ILOAD)2 (RL) RL = Inductor DC resistance (assume 0.1Ω) PINDUCTOR (1)2 (0.1) = 0.1W Only a portion of the temperature rise in the external inductor and diode is coupled to the junction of the LT1766. Based on empirical measurements the thermal effect on LT1766 junction temperature due to power dissipation in the external inductor and catch diode can be calculated as: ∆TJ(LT1766) ≈ (PDIODE + PINDUCTOR)(10°C/W) Using the example calculations for LT1766 dissipation, the LT1766 die temperature will be estimated as: TJ = TA + (θJA • PTOT) + [10 • (PDIODE + PINDUCTOR)] With the GN16 package ( θJA = 85°C/W), at an ambient temperature of 60 °C: TJ = 60 + (85 • 0.53) + (10 • 0.65) = 112°C With the TSSOP package ( θJA = 45°C/W), at an ambient temperature of 60 °C: TJ = 60 + (45 • 0.53) + (10 • 0.65) = 90°C APPLICATIO S I FOR ATIO Die temperature can peak for certain combinations of VIN, VOUT and load current. While higher VIN gives greater switch AC losses, quiescent and catch diode losses, a lower VIN may generate greater losses due to switch DC losses. In general, the maximum and minimum VIN levels should be checked with maximum typical load current for calculation of the LT1766 die temperature. If a more accurate die temperature is required, a measurement of the SYNC pin resistance (to GND) can be used. The SYNC pin resistance can be measured by forcing a voltage no greater than 0.5V at the pin and monitoring the pin current over temperature in an oven. This should be done with minimal device power (low VIN and no switching (VC = 0V)) in order to calibrate SYNC pin resistance with ambient (oven) temperature. Note: Some of the internal power dissipation in the IC, due to BOOST pin voltage, can be transferred outside of the IC to reduce junction temperature, by increasing the voltage drop in the path of the boost diode D2 (see Figure 9). This reduction of junction temperature inside the IC will allow higher ambient temperature operation for a given set of conditions. BOOST pin circuitry dissipates power given by: P VI V V DISS BOOST OUT SW C IN () •( / ) • = 36 2 Typically VC2 (the boost voltage across the capacitor C2) equals Vout. This is because diodes D1 and D2 can be considered almost equal, where: VC2 = VOUT – VFD2 – (–VFD1) = VOUT Hence the equation used for boost circuitry power dissipa- tion given in the previous Thermal Calculations section is stated as: P VI V V DISS BOOST OUT SW OUT IN () •( / )• = 36 Here it can be seen that boost power dissipation increases as the square of VOUT. It is possible, however, to reduce VC2 below VOUT to save power dissipation by increasing the voltage drop in the path of D2. Care should be taken that VC2 does not fall below the minimum 3.3V boost |
类似零件编号 - LT1940 |
|
类似说明 - LT1940 |
|
|
|
链接网址 |
| 隐私政策 |
| ALLDATASHEETCN.COM |
| ALLDATASHEET是否为您带来帮助? [ DONATE ] |
关于 Alldatasheet | 广告服务 | 联系我们 | 隐私政策 | 链接交换 | 制造商名单 All Rights Reserved©Alldatasheet.com |
| Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
|
Family Site : ic2ic.com |
icmetro.com |
Chinese ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
