MAX8688BLETG Просмотр технического описания (PDF) - Maxim Integrated

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MAX8688BLETG

Digital Power-Supply Controller/Monitor with PMBus Interface

Maxim Integrated 

Digital Power-Supply Controller/Monitor

with PMBus Interface

SCL

SYSTEM SDA

CONTROLLER IRQ

RST

SCL

SDA

FLT

MAX8688

RST

A3/ONOFF A2/SDAE A1/SCLE

SCL

SDA

FLT

MAX8688

RST

A3/ONOFF A2/SDAE A1/SCLE

SCL

SDA

FLT

MAX8688

RST

A3/ONOFF A2/SDAE A1/SCLE

RS+

RS-

ISN+

ISN-

DACOUT

ENOUT

RS+

RS-

ISN+

ISN-

DACOUT

ENOUT

RS+

RS-

ISN+

ISN-

DACOUT

ENOUT

VO+

VO-

IO+

IO-

POL 1

FB

EN

VO+

VO-

IO+

IO-

POL 2

FB

EN

VO+

VO-

IO+

IO-

POL 3

FB

EN

SCL

SDA

FLT

MAX8688

RST

A3/ONOFF A2/SDAE A1/SCLE

RS+

RS-

ISN+

ISN-

DACOUT

ENOUT

VO+

VO-

IO+

IO-

POL N

FB

EN

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

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 200Ω 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 to 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.

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