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NCV8851BDBGEVB

NCV8851B Automotive Grade Synchronous Buck Controller Evaluation Board User's Manual

ON Semiconductor 

NCV8851BDBGEVB

Table 4. BILL OF MATERIALS

Qty

Ref

Part

Part Description

1

RS1

25m

25mW 1% 2512 Thick-film SMD current

sense resistor

1

RV1

13.7k

13.7kW 1% 0.1W 0603 Thick-film SMD

resistor

1

R6

4.7

4.75W 1% 0.1W 0603 Thick-film SMD

resistor

4

TP1

VCC

0.291” X 0.109” Solder terminal turret Ag

over Cu

TP7

VOUT

0.291” X 0.109” Solder terminal turret Ag

over Cu

TP12

PGND

0.291” X 0.109” Solder terminal turret Ag

over Cu

TP13

PGND

0.291” X 0.109” Solder terminal turret Ag

over Cu

4

TP8

AGND

0.042” Inboard pin

TP9

AGND

0.042” Inboard pin

TP10

EN

0.042” Inboard pin

TP11

SYNC

0.042” Inboard pin

1

U1

NCV8851B Automotive synchronous buck controller

Manufacturer

Vishay/Dale

Yageo Corporation

Yageo Corporation

Mill-Max

Manufacturing

Corporation

Mill-Max

Manufacturing

Corporation

Mill-Max

Manufacturing

Corporation

Mill-Max

Manufacturing

Corporation

Vector Electronics

Vector Electronics

Vector Electronics

Vector Electronics

ON Semiconductor

Part Number

WSL2512R0250FEA

RC0603FR-0713K7L

RC0603FR-074R75L

2501-2-00-44-00-00-07-0

2501-2-00-44-00-00-07-0

2501-2-00-44-00-00-07-0

2501-2-00-44-00-00-07-0

K24C

K24C

K24C

K24C

NCV8851BG

EVALUATION BOARD MODIFICATIONS

Connecting EN to a Higher Voltage or VBATT

Typically, EN is tied to a logic output or low-voltage

supply. However, EN can be tied to a higher voltage or to

VBATT. In either case, if the supply that EN is tied to is

expected to go above 20 V, a current limiting resistor is

required.

For convenience, RN1 is unpopulated, disconnecting EN

from VBATT (via VIN) by default. To connect EN to VBATT,

populate RN1 with a current limiting resistor. To connect EN

to a separate higher voltage supply from VBATT, place a

current limiting resistor in series with the supply. Consult the

data sheet, NCV8851B/D, for selecting a current limiting

resistor.

Programming the Switching Frequency to a Different

Value

The switching frequency is programmed with a resistor,

RO1, from the ROSC pin to GND. By default, the switching

frequency is set to 170 kHz with a 51.1 kW resistor used for

RO1. The frequency can be programmed to a different value

by replacing RO1. Consult the data sheet, NCV8851B/D, for

selecting a different frequency program resistor.

Changing the switching frequency may impact dynamic

characteristics. Typically, increasing the switching

frequency allows the dynamic response to improve by

further optimization of the compensators; however, it is

advised to analyze dynamic response results of simulation

whenever the switching frequency is modified.

Synchronizing to a Higher Frequency

When connecting the SYNC input to a significantly

higher frequency than that set by the program resistor,

dynamic performance could be impaired. Based on

empirical results, it is advised to analyze dynamic response

results of simulation whenever SYNC is more than 33%

higher than the programmed switching frequency.

Adjusting the Current Limit

The current limit can be adjusted by using a different sense

resistor for RS1. Consult the data sheet, NCV8851B/D, for

selecting a different current limit.

Changing the sense resistor may impact dynamic

characteristics. It is advised to analyze dynamic response

results of simulation whenever the sense resistor is

modified.

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