MAX8688 datasheet(10/38 Pages) MAXIM

10 / 38 page

Digital Power-Supply Controller/Monitor

with PMBus Interface

______________________________________________________________________________________

MAX8688 Operating Modes

Reference Input (REFIN) Mode

Figure 3 shows the typical manner in which the

MAX8688 is used in an application where the POL has a

reference input, REFIN, to which it regulates its output

voltage between the VO+ and VO- terminals. In the

REFIN application, the DACOUT of the MAX8688 is con-

nected to the REFIN input of the POL. The output voltage

of the POL is sensed using RS+ and RS-. The sensed

voltage is suitably filtered by an internal 200

Ω resistor

and external capacitor connected to RS_C and is multi-

plexed to a 12-bit ADC that uses an accurate internal ref-

erence voltage. On receipt of either an OPERATION ON

command or a turn-on signal from A3/ONOFF, the

MAX8688 commences the startup operation that has

been programmed for the POL being controlled.

After the programmed tON_DELAY time, the MAX8688

open-drain ENOUT output goes active and the POL out-

put voltage is ramped up to its target VOUT_COMMAND

value precisely in the programmed tON_RISE time. This

facilitates easy implementation of tracking of multiple out-

put rails. On reaching the target output voltage, the

MAX8688 continuously monitors the POL output voltage

obtained at the RS+ and RS- inputs, and regulates it to

within ±0.2% for line, load, and temperature variations by

incrementing or decrementing the DACOUT output 1 LSB

(0.5mV) at a time. The MAX8688 output-voltage correc-

tion rate is programmable up to 10kHz by the

MFR_VOUT_CORRECTION_RATE parameter. Once the

requested target POL voltage is reached, it is possible to

easily margin up or down the POL voltage at a prepro-

grammed slew rate set by the parameter VOUT_TRANSI-

TION_RATE. To achieve this, the MAX8688 increments or

decrements the DACOUT output in a suitable number of

steps that depend on the programmed transition rate. In

addition,

the

user

needs

program

the

VOUT_SCALE_LOOP parameter equal to any voltage-

divider ratio implemented on the POL from its output volt-

age node to the inverting input of its error amplifier. This

allows the MAX8688 to correctly calculate the number of

DACOUT steps and voltage increments/decrements per

step and thus achieves the programmed rise time and

transition time.

SCL

SDA

SYSTEM

CONTROLLER

IRQ

RST

SCL

SDA

FLT

RST

A3/ONOFF A2/SDAE A1/SCLE

MAX8688

VO+

VO-

IO+

POL 1

IO-

RS+

RS-

ISN+

ISN-

DACOUT

ENOUT

SCL

SDA

FLT

RST

MAX8688

VO+

VO-

IO+

POL 2

IO-

RS+

RS-

ISN+

ISN-

DACOUT

ENOUT

SCL

SDA

FLT

RST

MAX8688

VO+

VO-

IO+

POL 3

IO-

RS+

RS-

ISN+

ISN-

DACOUT

ENOUT

SCL

SDA

FLT

RST

MAX8688

VO+

VO-

IO+

POL N

IO-

RS+

RS-

ISN+

ISN-

DACOUT

ENOUT

Figure 2. System Application Showing Multiple MAX8688s Controlling POL Power Supplies

MAX8688 датащи(PDF) 10 Page - Maxim Integrated Products

MAX8688 датащи(HTML) 10 Page - Maxim Integrated Products

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38

датащи скачать

ссылки URL