Datasheet LT1611 (Analog Devices) - 7
| Hersteller | Analog Devices |
| Beschreibung | Inverting 1.4MHz Switching Regulator in 5-Lead SOT-23 |
| Seiten / Seite | 12 / 7 — OPERATIO. Figure 7. Switching RL2 Provides 50mA to 150mA. Load Step for … |
| Dateiformat / Größe | PDF / 271 Kb |
| Dokumentensprache | Englisch |
OPERATIO. Figure 7. Switching RL2 Provides 50mA to 150mA. Load Step for LT1611 5V to – 5V Converter
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LT1611
U OPERATIO
C2 L1A L1B Figure 8 shows the output voltage with a 50mA to 150mA 1µF 22µH 22µH VIN load step, using an AVX TAJ “B” case 22µF tantalum 5V capacitor at the output. Output perturbation is approxi- D1 V –V IN SW OUT mately 100mV as the load changes from 50mA to 150mA. SHDN R + L2 Steady-state ripple voltage is 20mV R1 CPL 50Ω P–P, due to L1’s ripple LT1611 C1 RL1 NFB 100Ω current and C3’s ESR. Step response can be improved by C3 + GND R2 adding a 3.3nF capacitor (CPL) as shown in Figure 9. 10k Settling time improves from 150µs to 40µs, although steady-state ripple voltage does not improve. Figure 10 C1: AVX TAJB226M010 1611 F07 C2: TAIYO YUDEN LMK212BJ105MG pictures the output voltage and switch pin voltage at C3: SEE TEXT D1: MBR0520 200ns per division. Note the absence of high frequency L1A, L1B: SUMIDA CLS62-220 spikes at the output. This is easily repeatable with proper
Figure 7. Switching RL2 Provides 50mA to 150mA
layout, described in the next section.
Load Step for LT1611 5V to – 5V Converter
VOUT VOUT 50mV/DIV 20mV/DIV AC COUPLED AC COUPLED 150mA 150mA LOAD CURRENT LOAD CURRENT 50mA 50mA 100µs/DIV 1611 F08 20µs/DIV 1611 F09
Figure 8. Load Step Response of LT1611 Figure 9. Addition of CPL to Figure 7’s Circuit with 22
µ
F Tantalum Output Capacitor Improves Load Step Response. CPL = 3.3nF
VOUT 10mV/DIV SWITCH VOLTAGE 5V/DIV LOAD = 150mA 200ns/DIV 1611 F10
Figure 10. 22
µ
F “B” Case Tantalum Capacitor (AVX TAJ “B” Series) Has ESR Resulting in 20mVP–P Voltage Ripple at Output
7
U OPERATIO
C2 L1A L1B Figure 8 shows the output voltage with a 50mA to 150mA 1µF 22µH 22µH VIN load step, using an AVX TAJ “B” case 22µF tantalum 5V capacitor at the output. Output perturbation is approxi- D1 V –V IN SW OUT mately 100mV as the load changes from 50mA to 150mA. SHDN R + L2 Steady-state ripple voltage is 20mV R1 CPL 50Ω P–P, due to L1’s ripple LT1611 C1 RL1 NFB 100Ω current and C3’s ESR. Step response can be improved by C3 + GND R2 adding a 3.3nF capacitor (CPL) as shown in Figure 9. 10k Settling time improves from 150µs to 40µs, although steady-state ripple voltage does not improve. Figure 10 C1: AVX TAJB226M010 1611 F07 C2: TAIYO YUDEN LMK212BJ105MG pictures the output voltage and switch pin voltage at C3: SEE TEXT D1: MBR0520 200ns per division. Note the absence of high frequency L1A, L1B: SUMIDA CLS62-220 spikes at the output. This is easily repeatable with proper
Figure 7. Switching RL2 Provides 50mA to 150mA
layout, described in the next section.
Load Step for LT1611 5V to – 5V Converter
VOUT VOUT 50mV/DIV 20mV/DIV AC COUPLED AC COUPLED 150mA 150mA LOAD CURRENT LOAD CURRENT 50mA 50mA 100µs/DIV 1611 F08 20µs/DIV 1611 F09
Figure 8. Load Step Response of LT1611 Figure 9. Addition of CPL to Figure 7’s Circuit with 22
µ
F Tantalum Output Capacitor Improves Load Step Response. CPL = 3.3nF
VOUT 10mV/DIV SWITCH VOLTAGE 5V/DIV LOAD = 150mA 200ns/DIV 1611 F10
Figure 10. 22
µ
F “B” Case Tantalum Capacitor (AVX TAJ “B” Series) Has ESR Resulting in 20mVP–P Voltage Ripple at Output
7