19-3201; Rev 0; 1/08
Digital Power-Supply Controller/Monitor
with PMBus Interface
The MAX8688 is a fully integrated digital power-supply
controller and monitor IC that works with any existing
POL (point-of-load) power supply to provide complete
digital programmability. By interfacing to the reference
input, feedback node, and output enable, the MAX8688
takes control of the POL to provide functions such as
perfect tracking, sequencing, margining, and dynamic
adjustment of the output voltage.
The MAX8688 offers an accurate 12-bit analog-to-digi-
tal converter (ADC) accompanied with two differential
amplifiers for accurately monitoring both voltage and
current. An integrated 12-bit digital-to-analog converter
(DAC) is also available to margin power supplies as
well as dynamically adjust the output voltage with 0.2%
accuracy over temperature using this closed-loop sys-
tem. An internal temperature sensor provides an addi-
tional level of system monitoring.
The user-programmable registers provide flexible and
accurate control of time events such as a delay time
and transition period, monitoring for overvoltage and
undervoltage, overcurrent, reverse-current, overtemper-
ature fault and warning handling. The closed-loop oper-
ation is also programmable to make sure the MAX8688
works with any existing POL to provide superior regula-
tion accuracy and accurate margining.
The MAX8688 operates using a PMBus™-compliant
communication protocol. The device is programmed
using this protocol or simply with the use of a free
graphic-user interface (GUI) available from the Maxim
website that significantly reduces development time.
Once the configuration is complete, the results can be
saved into an EEPROM or loaded onto the part through
the PMBus at power-up. This allows remote configura-
tion of any POL using the MAX8688, replacing expen-
sive recalls or field service. Module current sharing is
also supported, since accurate current measurement
and fine resolution voltage control are available. The
MAX8688 can be programmed with up to 127 distinct
addresses to support large systems. The MAX8688 is
offered in a space-saving, 24-pin, lead-free 4mm x
4mm TQFN package.
DC-DC Modules and POLs
High-Reliability Infrastructure Equipment
PMBus is a trademark of SMIF, Inc.
o PMBus Interface for Programming, Monitoring,
Sequencing Up and Down, and Accurate Output-
o Controls Output Voltage with 0.2% Accuracy for
Line, Load, and Temperature Variations
o Output Voltage, Output Current, and Temperature
Monitoring with Adjustable Monitor Rate
o Current Measurement with 2.6% Accuracy and
Temperature Compensation Option
o Programmable Soft-Start and Soft-Stop Ramp
o Controls Up to 26 Power Supplies with Hardwired
Address Pins and Up to 127 POLs with Software
o Compatible with REFIN and FB Terminals of POL
o Protection for POL Against Overvoltage,
Undervoltage, Overcurrent, Negative Current and
Overtemperature Faults with No Action, Latch and
Retry (Hiccup) Options
o Open-Drain FLT Signal for Fault Detection
o Master-Slave Clocking Option Eliminates External
Clock Requirement and Provides Accurate Timing
o External EEPROM Interface for Auto-Programming
MAX8688ALETG+ -40°C to +85°C 24 TQFN-EP* T2444-4
MAX8688AHETG+ -40°C to +85°C 24 TQFN-EP* T2444-4
MAX8688BLETG+ -40°C to +85°C 24 TQFN-EP* T2444-4
MAX8688BHETG+ -40°C to +85°C 24 TQFN-EP* T2444-4
+Denotes a lead-free package.
*EP = Exposed pad.
Pin Configuration appears at end of data sheet.
________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.