Datasheet LT1616 (Analog Devices) - 8
| Manufacturer | Analog Devices |
| Description | 600mA, 1.4MHz Step-Down Switching Regulator in SOT-23 |
| Pages / Page | 16 / 8 — APPLICATIO S I FOR ATIO. Table 1. Inductor Vendors. Vendor. Phone. URL. … |
| File Format / Size | PDF / 288 Kb |
| Document Language | English |
APPLICATIO S I FOR ATIO. Table 1. Inductor Vendors. Vendor. Phone. URL. Part Series. Comments. Table 2. Capacitor Vendors
Model Line for this Datasheet
Text Version of Document
LT1616
U U W U APPLICATIO S I FOR ATIO Table 1. Inductor Vendors Vendor Phone URL Part Series Comments
Murata (404) 426-1300 www.murata.com LQH3C Small, Low Cost, 2mm Height Sumida (847) 956-0666 www.sumida.com CR43 CLS62 1:1 Coupled CLQ61 1.5mm Height Coilcraft (847) 639-6400 www.coilcraft.com DO1607C DO1608C DT1608C Coiltronics (407) 241-7876 www.coiltronics.com CTXxx-1 1:1 Coupled Toroid TP1 1.8mm Height Toko www.tokoam.com 3DF D52LC
Table 2. Capacitor Vendors Vendor Phone URL Part Series Comments
Taiyo-Yuden (408) 573-4150 www.t-yuden.com Ceramic Caps X5R Dielectric AVX (803) 448-9411 www.avxcorp.com Ceramic Caps Tantalum Caps Murata (404) 436-1300 www.murata.com Ceramic Caps in combination with a 0.1µF ceramic capacitor. However, Another constraint on the output capacitor is that it must input voltage ripple will be higher, and you may want to have greater energy storage than the inductor; if the stored include an additional 0.1µF ceramic a short distance away energy in the inductor is transferred to the output, you from the LT1616 circuit in order to filter the high frequency would like the resulting voltage step to be small compared ripple. The input capacitor should be rated for the maxi- to the regulation voltage. For a 5% overshoot, this require- mum input voltage. ment becomes The output capacitor has two essential functions. Along COUT > 10 • L(ILIM/VOUT)2 with the inductor, it filters the square wave generated by Finally, there must be enough capacitance for good tran- the LT1616 to produce the DC output. In this role it sient performance. The last equation gives a good starting determines the output ripple. The second function is to point. Alternatively, you can start with one of the designs store energy in order to satisfy transient loads and stabi- in this data sheet and experiment to get the desired lize the LT1616’s control loop. performance. Figure 3 illustrates some of the trade-off In most switching regulators the output ripple is deter- between different output capacitors. Figure 4 shows the mined by the equivalent series resistance (ESR) of the test circuit. The lowest trace shows total output current, output capacitor. Because the LT1616’s control loop doesn’t which jumps from 100mA to 250mA. The other traces depend on the output capacitor’s ESR for stable operation, show the output voltage ripple and transient response you are free to use ceramic capacitors to achieve very low with different output capacitors. The capacitor value, size output ripple and small circuit size. You can estimate and type are listed. Note that the time scale at 50µs per output ripple with the following equations: divison is much larger than the switching period, so you can’t see the output ripple at the switching frequency. The VRIPPLE = ∆IL • ESR for electrolytic capacitors (tantalum output ripple appears as vertical broadening of the trace. and aluminum) The first trace (COUT = 4.7µF) has peak-to-peak output VRIPPLE = ∆IL/(2π • f • COUT) for ceramic capacitors ripple of ~ 6mV, while the third trace shows peak-to-peak ripple of ~15mV. 8
U U W U APPLICATIO S I FOR ATIO Table 1. Inductor Vendors Vendor Phone URL Part Series Comments
Murata (404) 426-1300 www.murata.com LQH3C Small, Low Cost, 2mm Height Sumida (847) 956-0666 www.sumida.com CR43 CLS62 1:1 Coupled CLQ61 1.5mm Height Coilcraft (847) 639-6400 www.coilcraft.com DO1607C DO1608C DT1608C Coiltronics (407) 241-7876 www.coiltronics.com CTXxx-1 1:1 Coupled Toroid TP1 1.8mm Height Toko www.tokoam.com 3DF D52LC
Table 2. Capacitor Vendors Vendor Phone URL Part Series Comments
Taiyo-Yuden (408) 573-4150 www.t-yuden.com Ceramic Caps X5R Dielectric AVX (803) 448-9411 www.avxcorp.com Ceramic Caps Tantalum Caps Murata (404) 436-1300 www.murata.com Ceramic Caps in combination with a 0.1µF ceramic capacitor. However, Another constraint on the output capacitor is that it must input voltage ripple will be higher, and you may want to have greater energy storage than the inductor; if the stored include an additional 0.1µF ceramic a short distance away energy in the inductor is transferred to the output, you from the LT1616 circuit in order to filter the high frequency would like the resulting voltage step to be small compared ripple. The input capacitor should be rated for the maxi- to the regulation voltage. For a 5% overshoot, this require- mum input voltage. ment becomes The output capacitor has two essential functions. Along COUT > 10 • L(ILIM/VOUT)2 with the inductor, it filters the square wave generated by Finally, there must be enough capacitance for good tran- the LT1616 to produce the DC output. In this role it sient performance. The last equation gives a good starting determines the output ripple. The second function is to point. Alternatively, you can start with one of the designs store energy in order to satisfy transient loads and stabi- in this data sheet and experiment to get the desired lize the LT1616’s control loop. performance. Figure 3 illustrates some of the trade-off In most switching regulators the output ripple is deter- between different output capacitors. Figure 4 shows the mined by the equivalent series resistance (ESR) of the test circuit. The lowest trace shows total output current, output capacitor. Because the LT1616’s control loop doesn’t which jumps from 100mA to 250mA. The other traces depend on the output capacitor’s ESR for stable operation, show the output voltage ripple and transient response you are free to use ceramic capacitors to achieve very low with different output capacitors. The capacitor value, size output ripple and small circuit size. You can estimate and type are listed. Note that the time scale at 50µs per output ripple with the following equations: divison is much larger than the switching period, so you can’t see the output ripple at the switching frequency. The VRIPPLE = ∆IL • ESR for electrolytic capacitors (tantalum output ripple appears as vertical broadening of the trace. and aluminum) The first trace (COUT = 4.7µF) has peak-to-peak output VRIPPLE = ∆IL/(2π • f • COUT) for ceramic capacitors ripple of ~ 6mV, while the third trace shows peak-to-peak ripple of ~15mV. 8
