LT3435 Просмотр технического описания (PDF) - Linear Technology

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LT3435

High Voltage 3A, 500kHz Step-Down Switching Regulator with 100µA Quiescent Current

Linear Technology 

LT3435

ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating

temperature range, otherwise specifications are at TJ = 25°C. VIN = 12V, SHDN = 12V, BIAS = 5V, FB/PGFB = 1.25V, CSS/SYNC = 0V

unless otherwise noted.

SYMBOL

IPK

ICSS

IPGFB

VPGFB

ICT

VCT

PARAMETER

EA Source Current

EA Sink Current

VC to SW gm

VC High Clamp

SW Current Limit

Switch On Resistance (Note 9)

Switching Frequency

Maximum Duty Cycle

Minimum SYNC Amplitude

SYNC Frequency Range

SYNC Input Impedance

CSS Current Threshold (Note 10)

PGFB Input Current

PGFB Voltage Threshold (Note 11)

CT Source Current (Note 11)

CT Sink Current (Note 11)

CT Voltage Threshold (Note 11)

PG Leakage (Note 11)

PG Sink Current (Note 11)

CONDITIONS

FB = 1.15V

FB = 1.35V

FB = 1.15V

FB = 0V

PGFB = 1V, PG = 400mV

MIN TYP MAX UNITS

20

40

55

µA

15

30

40

µA

6

A/ V

2.1

2.2

2.4

V

●3

5.2

6.5

A

●

0.1

0.25

Ω

● 425

500

575

kHz

86

92

%

1.5

2.0

V

575

700

kHz

45

kΩ

7

13

20

µA

25

100

nA

● 88

90

92

%

2

3.6

5.5

µA

1

2

mA

1.16

1.2

1.26

V

0.1

1

µA

100 200

µA

Note 1: Absolute Maximum Ratings are those values beyond which the life of

a device may be impaired.

Note 2: The LT3435EFE is guaranteed to meet performance specifications

from 0°C to 125°C junction temperature. Specifications over the –40°C to

125°C operating junction temperature range are assured by design,

characterization and correlation with statistical process controls. The

LT3435IFE is guaranteed and tested over the full –40°C to 125°C operating

junction temperature range.

Note 3: Minimum input voltage is defined as the voltage where switching

starts. Actual minimum input voltage to maintain a regulated output will

depend upon output voltage and load current. See Applications Information.

Note 4: Supply input current is the quiescent current drawn by the input

pin. Its typical value depends on the voltage on the BIAS pin and operating

state of the LT3435. With the BIAS pin at 0V, all of the quiescent current

required to operate the LT3435 will be provided by the VIN pin. With the

BIAS voltage above its minimum input voltage, a portion of the total

quiescent current will be supplied by the BIAS pin. Supply sleep current is

defined as the quiescent current during the “sleep” portion of Burst Mode

operation. See Applications Information for determining application supply

currents.

Note 5: Minimum BIAS voltage is the voltage on the BIAS pin when IBIAS is

sourced into the pin.

Note 6: This is the minimum voltage across the boost capacitor needed to

guarantee full saturation of the internal power switch.

Note 7: Boost current is the current flowing into the BOOST pin with the pin

held 3.3V above input voltage. It flows only during switch on time.

Note 8: Gain is measured with a VC swing from 1.15V to 750mV.

Note 9: Switch on resistance is calculated by dividing VIN to SW voltage by the

forced current (3A). See Typical Performance Characteristics for the graph of

switch voltage at other currents.

Note 10: The CSS threshold is defined as the value of current sourced into the

CSS pin which results in an increase in sink current from the VC pin. See the

Soft-Start section in Applications Information.

Note 11: The PGFB threshold is defined as the percentage of VREF voltage

which causes the current source output of the CT pin to change from

sinking (below threshold) to sourcing current (above threshold). When

sourcing current, the voltage on the CT pin rises until it is clamped

internally. When the clamp is activated, the output of the PG pin will be set

to a high impedance state. When the CT clamp is inactive the PG pin will

be set active low with a current sink capability of 200µA.

3435f

3

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