LT1507 Просмотр технического описания (PDF) - Linear Technology

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LT1507

500kHz Monolithic Buck Mode Switching Regulator

Linear Technology 

LT1507

APPLICATIONS INFORMATION

components. In many cases only CC is needed. Adding RC

will improve phase margin, but this may necessitate the need

for CF to limit switching frequency ripple at the VC pin.

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

with a compensation capacitor (CC) of 0.0033µF, giving the

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

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)

80

200

VIN = 10V

VOUT = 5V, IOUT = 500mA

60

COUT = 100µF, 10V, AVX TPS

CC = 3.3nF, RC = 0

150

L = 10µH

40

GAIN

100

20

PHASE

50

0

0

–20

0.01

0.1

1

10 100

FREQUENCY (kHz)

–50

100

LT1511 • F10

Figure 10. Overall Loop Phase and Gain

Undervoltage Lockout

See Application Information in LT1376 data sheet.

PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted.

N8 Package

8-Lead PDIP (Narrow 0.300)

(LTC DWG # 05-08-1510)

0.300 – 0.325

(7.620 – 8.255)

0.045 – 0.065

(1.143 – 1.651)

0.130 ± 0.005

(3.302 ± 0.127)

0.009 – 0.015

(0.229 – 0.381)

+0.025

0.325 –0.015

( ) 8.255

+0.635

–0.381

0.065

(1.651)

TYP

0.005

(0.127)

MIN

0.100 ± 0.010

(2.540 ± 0.254)

0.125

(3.175)

MIN

0.015

(0.380)

MIN

0.255 ± 0.015*

(6.477 ± 0.381)

0.018 ± 0.003

(0.457 ± 0.076)

*THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.

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

0.400*

(10.160)

MAX

8

7

6

5

12

34

N8 0695

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.

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