Electronic Components Datasheet Search |
|
AAT4280-1 Datasheet(PDF) 11 Page - Advanced Analogic Technologies |
|
AAT4280-1 Datasheet(HTML) 11 Page - Advanced Analogic Technologies |
11 / 14 page AAT4280 Slew Rate Controlled Load Switch 4280.2006.11.1.4 11 For maximum current, refer to the following equation: IOUT(MAX) < ( PD(MAX) / RDS)1/2 For example, if VIN = 5V, RDS(MAX) = 154mΩ and TA = 25°C, IOUT(MAX) = 2.3A. If the output load current were to exceed 2.3A or if the ambient temperature were to increase, the internal die temperature would increase, and the device would be damaged. Higher peak currents can be obtained with the AAT4280. To accomplish this, the device thermal resistance must be reduced by increasing the heat sink area or by operating the load switch in a duty- cycle manner. High Peak Output Current Applications Some applications require the load switch to oper- ate at a continuous nominal current level with short duration, high-current peaks. The duty cycle for both output current levels must be taken into account. To do so, first calculate the power dissi- pation at the nominal continuous current level, and then add in the additional power dissipation due to the short duration, high-current peak scaled by the duty factor. For example, a 4V system using an AAT4280 oper- ates at a continuous 100mA load current level and has short 2A current peaks, as in a GSM applica- tion. The current peak occurs for 576µs out of a 4.61ms period. First, the current duty cycle is calculated: % Peak Duty Cycle: X/100 = 576µs/4.61ms % Peak Duty Cycle = 12.5% The load current is 100mA for 87.5% of the 4.61ms period and 2A for 12.5% of the period. Since the Electrical Characteristics do not report RDS(MAX) for 4V operation, it must be calculated approximately by consulting the chart of RDS(ON) vs. VIN. The RDS reported for 5V can be scaled by the ratio seen in the chart to derive the RDS for a 4V VIN: 120mΩ · 87m Ω /80mΩ = 130mΩ. De-rated for temperature: 130m Ω x (1 + 0.0028 · (125°C -25°C)) = 166mΩ. The power dissipation for a 100mA load is calculat- ed as follows: PD(MAX) = IOUT2 · RDS PD(100mA) = (100mA)2 · 166mΩ PD(100mA) = 1.66mW PD(87.5%D/C) = %DC · PD(100mA) PD(87.5%D/C) = 0.875 · 1.66mW PD(87.5%D/C) = 1.45mW The power dissipation for 100mA load at 87.5% duty cycle is 1.45mW. Now the power dissipation for the remaining 12.5% of the duty cycle at 2A is calculated: PD(MAX) = IOUT2 · RDS PD(2A) = (2A)2 · 166mΩ PD(2A) = 664mW PD(12.5%D/C) = %DC · PD(2A) PD(12.5%D/C) = 0.125 · 664mW PD(12.5%D/C) = 83mW The power dissipation for 2A load at 12.5% duty cycle is 83mW. Finally, the two power figures are summed to determine the total true power dissipa- tion under the varied load. PD(total) = PD(100mA) + PD(2A) PD(total) = 1.45mW + 83mW PD(total) = 84.5mW The maximum power dissipation for the AAT4280 operating at an ambient temperature of 85°C is 333mW. The device in this example will have a total power dissipation of 84.5mW. This is well within the thermal limits for safe operation of the device; in fact, at 85°C, the AAT4280 will handle a 2A pulse for up to 50% duty cycle. At lower ambi- ent temperatures, the duty cycle can be further increased. |
Similar Part No. - AAT4280-1 |
|
Similar Description - AAT4280-1 |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.NET |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Contact us | Privacy Policy | Link Exchange | Manufacturer List 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 |