DC1185B-A Datasheet DC1185B-A | P4-P6

dc1185b-a/-bf

DEMO MANUAL

DC1185B-A/-B

RAIL TRACKING

Demonstration circuit 1185 is set up for independent

turn-on of VOUT1 and VOUT2. The ramp-rate for VOUT1 is

determined by the TRK/SS1 capacitor at C2 and the ramp-

rate for VOUT2 is determined by the TRK/SS2 capacitor

at C47. The turn-on of one rail will not affect the other for

the original demo board.

This board can be modified on the bench to allow VOUT1

to track an external signal. It can also be modified to

allow VOUT

2 to track VOUT1 or to allow VOUT2 to track

external signal. Tables 2 and 3 cover the rail tracking

options for each rail, with the DC3850B-B version used

as an example.

Table 1. VOUT1 Tracking Options for a 1.5V Output

TRACK 1 DIVIDER TRK/SS1 CAPACITOR

CONFIGURATION R3 R2 C2

Soft-Start without Tracking (Original Board) 0Ω Not Stuffed 0.1µF

External Coincident Tracking 17.8kΩ 20.0kΩ Not Stuffed

Table 2. VOUT2 Tracking Options for a 1.2V Output

TRACK 2 DIVIDER TRK/SS2 CAPACITOR

CONFIGURATION R36 R34 R37 C47

Soft-Start without Tracking (Original Board) 0Ω Not Stuffed Not Stuffed 0.1µF

Coincident Tracking to VOUT1 (1.5V) 0Ω 10.0kΩ 20.0kΩ Not Stuffed

External Coincident Tracking 10.0kΩ Not Stuffed 20.0kΩ Not Stuffed

dc1185b-a/-bf

DEMO MANUAL

DC1185B-A/-B

INDUCTOR DCR SENSING

Demonstration circuit 1185 provides an optional circuit

for DCR sensing. DCR sensing uses the DCR of the in-

ductor to

sense the inductor current instead of discrete

sense

resistors. The advantages of DCR sensing are lower

cost, reduced board space and higher efficiency, but the

disadvantage is a less accurate current limit. If DCR sens

ing is used, be sure to select an inductor current with a

sufficiently

high saturation current or use an iron powder

type. Tables 3 and 4 show an example of how to modify

the DC1185 for DCR sensing using these parameters:

OUT1

= 2.0V/10A

OUT2

= 1.8V/10A

= 6.5V to 14V

= 500kHz, typical

L1, L2 = Toko FDU0650-R56M=P3

(0.56µH, DCR = 2.45mΩ Typ, 3.2

mΩ Max)

ILIM = Floating (R42, R44 = Open)

Table 3. V

OUT1

Configured as a 2.0V/10A Converter Using DCR Sensing and Discrete Sense Resistors

SENSE

FILTER

RESISTORS

SENSE FIILTER

CAPACITOR

DCR FILTER/DIVIDER RESISTORS

SENSE1– TO L1–

JUMPERTOP BOTTOM

CONFIGURATION RS1 L1 R29, R30 C14 R45 R47 R61

DCR Sensing Short with Cu

Strip or Very

Short and Thick

Piece of Wire

Toko

FDU0650-R56M=P3

Open 0.1µF

2.37kΩ 6.49kΩ 0Ω

Discrete R

SENSE

(Original Board)

3mΩ

2010 Package

Toko

FDU0650-R56M=P3

100Ω 1nF Open Open Open

Table 4. V

OUT2

Configured as a 1.8V/10A Converter Using DCR Sensing and Discrete Sense Resistors

SENSE

FILTER

RESISTORS

SENSE FIILTER

CAPACITOR

DCR FILTER/DIVIDER RESISTORS

SENSE1– TO L1–

JUMPERTOP BOTTOM

CONFIGURATION RS2 L2 R39, R40 C15 R51 R53 R62

DCR Sensing Short with Cu

Strip or Very

Short and Thick

Piece of Wire

Toko

FDU0650-R56M=P3

Open 0.1µF

2.37kΩ 6.49kΩ 0Ω

Discrete R

SENSE

(Original Board)

3mΩ

2010 Package

Toko

FDU0650-R56M=P3

100Ω 1nF Open Open Open

dc1185b-a/-bf

DEMO MANUAL

DC1185B-A/-B

SYNCHRONIZATION TO AN EXTERNAL CLOCK

The LTC3850 uses a phase-lock-loop which forces its

internal clock to be synchronized to an external clock.

Once synchronized, the rising edge of the top FET gate is

aligned to the rising edge of the external clock. The external

clock signal needs to be applied to the LTC3850’s MODE

pin which is tied to the turret labeled SYNC. The internal

phase lock loop is stabilized by a network on the FREQ pin

of the LTC3850. To set up the DC1185 for synchronization

to an external clock, follow the steps below.

1. Remove R7.

2. Stuff 10kΩ at R8.

3. Stuff 10nF at R10.

4. Leave 1nF at C12.

5. Float the MODE pin by placing the MODE jumper in the

BM position.

6. Apply the external clock from the turret la-beled SYNC

to GND.

P1-P3 P4-P6 P7-P9 P10-P10

DC1185B-A

Mfr. #:

Buy DC1185B-A

Manufacturer:

Analog Devices Inc.

Description:

Power Management IC Development Tools LTC3850EUF Demo Board - 4.5V ? VIN ? 14V

Lifecycle:

New from this manufacturer.

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DC1185B-A