LTC6990IDCB-TRPB Просмотр технического описания (PDF) - Analog Devices

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LTC6990IDCB-TRPB

TimerBlox: Voltage Controlled Silicon Oscillator

Analog Devices 

LTC6990

APPLICATIONS INFORMATION

Modulation Bandwidth and Settling Time

The LTC6990 will respond to changes in ISET up to a –3dB

bandwidth of 0.4 • fOUT (see Figure 15). This makes it easy

to stabilize a feedback loop around the LTC6990, since it

does not introduce a low-frequency pole.

Settling time depends on the master oscillator frequency.

Following a 2x or 0.5x step change in ISET, the output

frequency takes approximately six master clock cycles

(6 • tMASTER) to settle to within 1% of the final value. An

example is shown in Figure 16.

0

VCTRL = 0.536V + 0.278V

• SIN(2π•fMOD•t)

fOUT =18.75kHz ±10%

–10

–3dB AT 0.4•fOUT

–20

Power Supply Current

The power supply current varies with frequency, supply

voltage and output loading. It can be estimated under any

condition using the following equation:

IS(TYP) ≈ V+• fMASTER • 7pF + V+• f OUT•(13pF + CLOAD)

+

V+

480kΩ

+

2

•

V+

RLOAD

+

1.75

•ISET

+

50µA

The equation is also valid for OE = 0 (output disabled),

with fOUT = 0Hz.

VCTRL

2V/DIV

OUT

2V/DIV

–30

RSET = 200k

RVCO = 464k

DIVCODE = 4(÷16)

–40

0.1

1

fMOD/fOUT (Hz/Hz)

10

6990 F15

Figure 15. Modulation Frequency Response

fOUT

50kHz/DIV

10µs/DIV

V+ = 3.3V, DIVCODE = 0

RSET = 200k, RVCO = 464k

fOUT = 175kHz AND 350kHz

Figure 16. Settling Time

6990 F16

Rev. D

20

For more information www.analog.com

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