LT1572 Просмотр технического описания (PDF) - Linear Technology

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LT1572

100kHz, 1.25A Switching Regulator with Catch Diode

Linear Technology 

LT1572

ABSOLUTE AXI U RATI GS

Supply Voltage (Note 4).......................................... 40V

Switch Output Voltage (Note 4) .............................. 60V

Feedback Pin Voltage (Transient, 1ms) ................ ±15V

Operating Junction Temperature Range

Operating .............................................. 0°C to 100°C

Short Circuit ......................................... 0°C to 125°C

Storage Temperature Range ............... – 65°C to 150°C

Lead Temperature (Soldering, 10 sec)................. 300°C

DIODE

Average Forward Current .......................................... 1A

Peak Repetitive Forward Current .............................. 2A

Peak Non-Repetitive Forward Current....................... 3A

Peak Repetitive Reverse Voltage............................. 20V

Continuous (Average) Reverse Voltage .................. 15V

Operating Junction Temperature ......................... 125°C

PACKAGE/ORDER I FOR ATIO

NC 1

ANODE* 2

CATHODE* 3

GND 4

VC 5

FB 6

NC 7

NC 8

TOP VIEW

16 NC

15 ANODE*

14 CATHODE*

13 GND

12 E2

11 VSW

10 E1

9 VIN

ORDER PART

NUMBER

LT1572CS

S PACKAGE

16-LEAD PLASTIC SO

*ALWAYS CONNECT BOTH ANODE

AND BOTH CATHODE PINS

TJMAX (REGULATOR) = 100°C

TJMAX (DIODE) = 125°C

SEE THERMAL MANAGEMENT SECTION FOR θJA

Consult factory for Industrial and Military grade parts.

Note 1: Minimum effective switch “on” time for the LT1572 (in current

limit only) is ≈ 0.6µs. This limits the maximum safe input voltage during

an output shorted condition. Buck mode and inverting mode input voltage

during an output shorted condition is limited to:

VIN (max, output shorted)

buck and inverting mode

=

15V

+

R

× IL

t×

+

f

Vf

R = Inductor DC resistance

IL = 2.5A

Vf = Output catch diode forward voltage at IL

t = 0.6µs, f = 100kHz switching frequency

Maximum input voltage can be increased by increasing R or Vf.

External current limiting such as that shown in AN19, Figure 39, will

provide protection up to the full supply voltage rating. C1 in Figure 39

should be reduced to 200pF.

Transformer designs will tolerate much higher input voltages because

leakage inductance limits rate of rise of current in the switch. These

designs must be evaluated individually to assure that current limit is well

controlled up to maximum input voltage.

Boost mode designs are never protected against output shorts because

the external catch diode and inductor connect input to output.

ELECTRICAL CHARACTERISTICS VIN = 15V, VC = 0.5V, VFB = VREF, output pin open, unless otherwise noted.

SYMBOL PARAMETER

VREF

Reference Voltage

IB

Feedback Input Current

gm

Error Amplifier

Transconductance

Error Amplifier Source or

Sink Current

Error Amplifier Clamp

Voltage

Reference Voltage Line

Regulation

AV

Error Amplifier Voltage Gain

Minimum Input Voltage (Note 3)

IQ

Supply Current

CONDITIONS

Measured at Feedback Pin

VC = 0.8V

VFB = VREF

∆IC = ±25µA

VC = 1.5V

Hi Clamp, VFB = 1V

Lo Clamp, VFB = 1.5V

3V ≤ VIN ≤ 40V

VC = 0.8V

0.9V ≤ VC ≤ 1.4V

3V ≤ VIN ≤ 40V, VC = 0.6V

MIN TYP MAX UNITS

1.224 1.244 1.264

V

q 1.214 1.244 1.274

V

350 750

nA

q

1100

nA

3000 4400 6000 µmho

q 2400

7000 µmho

150 200 350

µA

q

120

400

µA

1.80

2.30

V

0.25 0.38 0.52

V

q

0.03

%/ V

500 800

V/ V

q

2.6 3.0

V

6

9

mA

2

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