LTC3416 Ver la hoja de datos (PDF) - Linear Technology

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LTC3416

4A, 4MHz, Monolithic Synchronous Step-Down Regulator with Tracking

Linear Technology 

LTC3416

APPLICATIO S I FOR ATIO

coincidentally or ratiometrically track another output volt-

age as shown in Figure 3.

If the voltage on the TRACK pin is less than 0.8V, voltage

tracking is enabled. During voltage tracking, the output

voltage regulates to the tracking voltage through a resistor

divider network. The output voltage during tracking can be

calculated with the following equation:

VOUT = VTRACK1+ RR21 , VTRACK < 0.8V

Voltage tracking can be accomplished by sensing a frac-

tion of the output voltage from another regulator. This is

typically done by using a resistor divider to attenuate the

output voltage that is being tracked. Setting this attenua-

tion factor equal to the reciprocal of the gain factor

provided by the feedback resistors will force the regulator

outputs to be equal to each other during tracking. If

tracking is not desired, connect the TRACK pin to SVIN.

To implement the coincident tracking shown in Figure 3a,

connect an extra resistor divider to the output of VOUT2 and

connect its midpoint to the TRACK pin of the LTC3416 as

shown in Figure 4. The ratio of this divider should be

selected the same as that of VOUT1’s resistor divider. To

implement the ratiometric sequencing in Figure 3b, no

extra resistor divider is necessary. Simply connect the

TRACK pin to VFB(MASTER).

An alternative method of tracking is shown in Figure 5. For

the circuit of Figure 5, the following equations can be used

to determine the resistor values:

VOUT1 = 0.8V1+ RR21

VOUT2 = 0.8V1+ R4R+3R5

R4

=

R3

VOUT2

VOUT1

–

1

VOUT2

VOUT1

VOUT2

VOUT1

TIME

(3a) Coincident Tracking

TIME

3416 F03

(3b) Ratiometric Sequencing

Figure 3. Two Different Modes of Output Voltage Sequencing

VOUT2

TO

TRACK

PIN

R4 R2

TO

VFB(MASTER)

PIN

R3 R1

VOUT2

TO

TRACK

PIN

R2

TO

VFB(MASTER)

PIN

R1

(4a) Coincident Tracking Setup

3416 F04

(4b) Ratiometric Setup

Figure 4. Setup for Tracking and Ratiometric Sequencing

3416f

10

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