7

LT1611

Figure 8 shows the output voltage with a 50mA to 150mA

load step, using an AVX TAJ “B” case 22

µF tantalum

capacitor at the output. Output perturbation is approxi-

mately 100mV as the load changes from 50mA to 150mA.

current and C3’s ESR. Step response can be improved by

Settling time improves from 150

µs to 40µs, although

steady-state ripple voltage does not improve. Figure 10

pictures the output voltage and switch pin voltage at

200ns per division. Note the absence of high frequency

spikes at the output. This is easily repeatable with proper

layout, described in the next section.

OPERATIO

5V

1611 F07

SW

L1A

22

µH

L1B

22

µH

D1

GND

LT1611

C1: AVX TAJB226M010

C2: TAIYO YUDEN LMK212BJ105MG

C3: SEE TEXT

D1: MBR0520

L1A, L1B: SUMIDA CLS62-220

C1

C3

C2

1

µF

R2

10k

R1

NFB

SHDN

+

100

Ω

50

Ω

Load Step for LT1611 5V to – 5V Converter

Figure 8. Load Step Response of LT1611

with 22

µF Tantalum Output Capacitor

Figure 10. 22

µF “B” Case Tantalum Capacitor (AVX TAJ “B” Series)

50mV/DIV

AC COUPLED

LOAD CURRENT

150mA

50mA

100

µs/DIV

1611 F08

20mV/DIV

AC COUPLED

LOAD CURRENT

150mA

50mA

20

µs/DIV

1611 F09

10mV/DIV

SWITCH VOLTAGE

5V/DIV

LOAD = 150mA

200ns/DIV

1611 F10