LT3579IUFD-1-PBF(RevA) View Datasheet(PDF) - Linear Technology

Part Name

Description

Manufacturer

LT3579IUFD-1-PBF
(Rev.:RevA)

6A Boost/Inverting DC/DC Converter with Fault Protection

Linear Technology 

APPENDIX

The current mode zero (Z3) is a right half plane zero

which can be an issue in feedback control design, but is

manageable with proper external component selection.

Using the circuit in Figure 20 as an example, Table 8 shows

the parameters used to generate the Bode plot shown in

Figure 19.

Table 8. Bode Plot Parameters

PARAMETER VALUE

UNITS

RL

7

Ω

COUT

30

µF

RESR

2

mΩ

R0

305

kΩ

CC

2200

pF

CF

47

pF

CPL

0

pF

RC

8

kΩ

R1

130

kΩ

R2

14.6

kΩ

VOUT

12

V

VIN

5

V

gma

250

µmho

gmp

28

mho

L

2.2

µH

fOSC

1.0

MHz

COMMENT

Application Specific

Application Specific

Application Specific

Not Adjustable

Adjustable

Optional/Adjustable

Optional/Adjustable

Adjustable

Adjustable

Not Adjustable

Application Specific

Application Specific

Not Adjustable

Not Adjustable

Application Specific

Adjustable

From Figure 19, the phase is –134° when the gain reaches

0dB giving a phase margin of 46°. The crossover frequency

is 8kHz, which is more than three times lower than the

frequency of the RHP zero Z3 to achieve adequate phase

margin.

LT3579/LT3579-1

140

0

120

–45

PHASE

100

–90

80

–135

60

40

GAIN

20

46° AT

8kHz

–180

–225

–270

0

–315

–20

–360

10

100

1k

10k 100k 1M

FREQUENCY (Hz)

35791 F19

Figure 19. Bode Plot for Example Boost Converter

L1

2.2µH

D1

VIN

5V

VOUT

12V

1.7A

SW1 SW2

130k

CIN

22µF

VIN

FB

100k

LT3579

FAULT

GATE

SHDN

CLKOUT

COUT

10µF

×3

RT

SYNC GND

86.6k

VC

SS

0.1µF

47pF 8k

2.2nF

35791 F20

Figure 20. 5V to 12V Boost Converter

For more information www.linear.com/LT3579

35791fa

31

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