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Deadtime_gctrl, Zeta_p – Maxim Integrated MAX15301 PMBus Command Set User Manual

Page 52

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MAX15301 PMBus Command Set User’s Guide

Rev 1

Page 52 of 53

DEADTIME_GCTRL

255

-1200

Note: the default setting is LXDAC = 15 and this value should not be changed.

Variable Gate-Drive Voltage
The MAX15301 allows adjustment of the gate drive voltage from approximately 5.2V to 8.7V, as
controlled by a 4-bit DAC. The DAC value to gate-drive voltage relationship is as follows:

GCTRLDAC

Setting

Typical

Gate Drive (V)

0

5.2

1

5.4

2

5.7

3

5.9

4

6.1

5

6.4

6

6.6

7

6.8

8

7.1

9

7.3

10

7.5

11

7.8

12

8

13

8.2

14

8.5

15

8.7

The variable gate drive system has two modes of operation, controlled by bit 6 of the

LOOP_CONFIG

command. When bit 6 is set to 1, the value of READ_IOUT is compared to determine which of “eighth”
of the full load current range the device is operating in; e.g. 0 to IMAX/8, IMAX/8 to IMAX/4, etc. For
each “bin” of the full load current range, there is a corresponding DAC setting in a lookup table. This
table is populated by values sent in the GCTRL[0] to GCTRL[7] arguments of DEADTIME_GCTRL.

When bit 6 of LOOP_CONFIG is set to 0, the MAX15301 uses one setting for the gate-drive voltage,
regardless of load current. This “fixed” setting is given by the GCTRLDAC argument of DEADTIME_GCTRL.

Wait at least 500ms for execution after sending the DEADTIME_GCTRL command before sending
additional PMBus commands.

ZETA_P

Reference:

Maxim Specific

Lockable:

Yes

Command Code:

0xE8

Format:

Linear

Data Bytes:

2

Units:

Scalar

Transfer:

Read/Write Byte

Factory Value:

0xBB00 (1.5)

Description/Notes:

The ZETA_P command sets the damping ratio for the closed-loop response. The value can be changed
to improve performance when using nonceramic output capacitors with higher equivalent series
resistance.