LTC1736 데이터 시트보기 (PDF) - Linear Technology

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LTC1736

5-Bit Adjustable High Efficiency Synchronous Step-Down Switching Regulator

Linear Technology 

LTC1736

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

temperature range, otherwise specifications are at TA = 25°C. VIN = 15V, VRUN/SS = 5V unless otherwise noted.

SYMBOL

PARAMETER

CONDITIONS

MIN TYP MAX UNITS

BG tr

BG tf

TG/BG T1D

BG Transition Time:

Rise Time

Fall Time

Top Gate Off to Synchronous

Gate-On Delay Time

(Note 9)

CLOAD = 3300pF

CLOAD = 3300pF

CLOAD = 3300pF Each Driver

50

90

ns

40

80

ns

100

ns

TG/BG T2D

Synchronous Gate Off to Top

Gate-On Delay Time

CLOAD = 3300pF Each Driver

70

ns

Internal VCC Regulator

VINTVCC

Internal VCC Voltage

VLDO(INT)

Internal VCC Load Regulation

VLDO(EXT)

EXTVCC Drop Voltage

VEXTVCC

EXTVCC Switchover Voltage

VEXTVCC(HYS) EXTVCC Hysteresis

Oscillator

6V < VIN < 30V, VEXTVCC = 4V

ICC = 0mA to 20mA, VEXTVCC = 4V

ICC = 20mA, VEXTVCC = 5V

ICC = 20mA, EXTVCC Ramping Positive

5.0

5.2

5.4

V

0.2

1

%

130 200

mV

q 4.5

4.7

V

0.2

V

fOSC

fH/fOSC

fFCB(SYNC)

PGOOD Output

Oscillator Frequency

Maximum Sync Frequency Ratio

FCB Pin Threshold For Sync

(Note 5), COSC = 43pF

Ramping Negative

265 300 335

kHz

1.3

0.9

1.2

V

VPGL

IPGOOD

VPG

PGOOD Voltage Low

PGOOD Leakage Current

PGOOD Trip Level

VID Control

IPGOOD = 2mA

VPGOOD = 5V

VOSENSE with Respect to Set Output Voltage

VOSENSE Ramping Negative

VOSENSE Ramping Positive

110 200

mV

±1

µA

– 6.0 – 7.5 – 9.5

%

6.0

7.5

9.5

%

VIDVCC

IVIDVCC

RVFB/VOSENSE

RRATIO

RPULL-UP

VIDT

IVIDLEAK

VPULL-UP

VID Operating Supply Voltage

VID Supply Current

Resistance Between VOSENSE and VFB

Resistor Ratio Accuracy

VID0 to VID4 Pull-Up Resistance

VID Input Voltage Threshold

VID Input Leakage Current

VID Pull-Up Voltage

(Note 6) VIDVCC = 3.3V

Programmed from 0.925V to 2.00V

(Note 7) VDIODE = 0.6V

(Note 7) VIDVCC < VID < 7V

VIDVCC = 3.3V

VIDVCC = 5V

2.7

5.5

V

0.01

5

µA

10

kΩ

± 0.05

%

40

kΩ

0.4

1.0

1.6

V

0.01

±1

µA

2.8

V

4.5

V

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

of a device may be impaired.

Note 2: TJ is calculated from the ambient temperature TA and power

dissipation PD according to the following formulas:

LTC1736CG, LTC1736IG: TJ = TA + (PD • 110°C/W)

Note 3: The LTC1736 is tested in a feedback loop that servos VFB to the

balance point for the error amplifier (VITH = 1.2V).

Note 4: Dynamic supply current is higher due to the gate charge being

delivered at the switching frequency. See Applications Information.

Note 5: Oscillator frequency is tested by measuring the COSC charge

current (IOSC) and applying the formula:

fOSC

=







8.477(1011) 

COSC(pF) + 11

1

 ICHG

+

1

IDIS 

–1

Note 6: With all five VID inputs floating (or tied to VIDVCC) the VIDVCC

current is typically < 1µA. However, the VIDVCC current will rise and be

approximately equal to the number of grounded VID input pins times

(VIDVCC – 0.6V)/40k. (See the Applications Information section for more

detail.)

Note 7: Each built-in pull-up resistor attached to the VID inputs also has a

series diode to allow input voltages higher than the VIDVCC supply without

damage or clamping. (See the Applications Information section for more

detail.)

Note 8: The minimum on-time condition corresponds to the on inductor

peak-to-peak ripple current ≥ 40% of IMAX (see minimum on-time

considerations in the Applications Information section).

Note 9: Rise and fall times are measured using 10% and 90% levels. Delay

times are measured using 50% levels.

3

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