19

LT1507

move around, but at the same time phase moves with it so

that adequate phase margin is maintained over a very wide

range of ESR (

≥ 5:1)

Undervoltage Lockout

See Application Information in LT1376 data sheet.

N8 0695

0.005

(0.127)

MIN

0.100

± 0.010

(2.540

± 0.254)

0.065

(1.651)

TYP

0.045 – 0.065

(1.143 – 1.651)

0.130

± 0.005

(3.302

± 0.127)

0.015

(0.380)

MIN

0.018

± 0.003

(0.457

± 0.076)

0.125

(3.175)

MIN

12

3

4

87

6

5

0.255

± 0.015*

(6.477

± 0.381)

0.400*

(10.160)

MAX

0.009 – 0.015

(0.229 – 0.381)

0.300 – 0.325

(7.620 – 8.255)

0.325

+0.025

–0.015

+0.635

–0.381

8.255

()

*THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.

MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.010 INCH (0.254mm)

N8 Package

8-Lead PDIP (Narrow 0.300)

(LTC DWG # 05-08-1510)

will improve phase margin, but this may necessitate the need

In Figure 10, full loop phase/gain characteristics are shown

error amplifier a pole at 240Hz, with phase rolling off to 90

°

and staying there. The overall loop has a gain of 77dB at low

frequency rolling off to unity gain at 20kHz. Phase shows a

2-pole characteristic until the ESR of the output capacitor

brings it back above 10kHz. Phase margin is about 60

° at

unity-gain.

Analog experts will note that around 1kHz, phase dips to

within 20

° of the zero phase margin line. This is typical of

switching regulators because of the 2-pole rolloff generated

by the output capacitor and the compensation network. This

region of low phase is not a problem as long as it does not

occur near unity-gain. In practice, the variability of output

capacitor ESR tends to dominate all other effects with respect

to loop response. Variations in ESR

will cause unity-gain to

FREQUENCY (kHz)

80

60

40

20

0

–20

200

150

100

50

0

–50

0.01

1

0.1

10

100

100

LT1511 • F10

L = 10

µH

GAIN

PHASE

Figure 10. Overall Loop Phase and Gain

Information furnished by Linear Technology Corporation is believed to be accurate and reliable.

However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-

tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.

Dimensions in inches (millimeters) unless otherwise noted.