19-3201; Rev 2; 2/11
KIT
ATION
EVALU
BLE
AVAILA
Digital Power-Supply Controller/Monitor
with PMBus Interface
General Description
The MAX8688 fully integrated digital power-supply con-
troller and monitor IC 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 adjust-
ment 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.
Features
o
PMBus Interface for Programming, Monitoring,
Sequencing Up and Down, and Accurate Output-
Voltage Control
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
o
Programmable Soft-Start and Soft-Stop Ramp
Rates
o
Controls Up to 26 Power Supplies with Hardwired
Address Pins and Up to 127 POLs with Software
Addressing
o
Compatible with REFIN and FB Terminals of POL
Power Supplies
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
Reference
o
External EEPROM Interface for Auto-Programming
on Power-Up
MAX8688
Ordering Information
PART
MAX8688ALETG+
MAX8688AHETG+
MAX8688BLETG+
MAX8688BHETG+
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
24 TQFN-EP*
24 TQFN-EP*
24 TQFN-EP*
24 TQFN-EP*
+Denotes
a lead(Pb)-free/RoHS-compliant package.
*EP
= Exposed pad.
Applications
Telecom Networking
DC-DC Modules and POLs
Servers
High-Reliability Infrastructure Equipment
PMBus is a trademark of SMIF, Inc.
PART
MAX8688ALETG+
MAX8688AHETG+
MAX8688BLETG+
MAX8688BHETG+
0.2
0.2
0.4
0.4
Selector Guide
ACCURACY
(%)
ENOUT POWER-UP
DEFAULT STATE
Low
High
Low
High
Pin Configuration appears at end of data sheet.
1
________________________________________________________________
Maxim Integrated Products
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.
Digital Power-Supply Controller/Monitor
with PMBus Interface
MAX8688
ABSOLUTE MAXIMUM RATINGS
AVDD, DVDD to AGND .........................................-0.3V to +4.5V
DGND to AGND ..................................................................±0.3V
RS+, RS-, ISN+, ISN- to AGND ................................-0.3V to +6V
RS_C, ISN_C, A1/SCLE, A2/SDAE,
A3/ONOFF to AGND............................-0.3V to (V
AVDD
+ 0.3V)
DACOUT to AGND .................................-0.3V to (V
AVDD
+ 0.3V)
REFO to AGND......................................................-0.3V to +4.5V
Continuous Power Dissipation (T
A
= +70°C)
24-Pin TQFN (derate 27.8mW/°C above +70°C)...........2222mW*
Note 1:
Hand soldering not recommended.
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
SCL, SDA, CLKIO,
RST
to DGND .........................-0.3V to +4.5V
ENOUT,
FLT
to DGND..............................................-0.3V to +6V
Thermal Resistance from Junction to Exposed Pad ......2.7°C/W
Operating Temperature .......................................-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature.........................................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Soldering Temperature (reflow) (Note 1) .........................+260°C
PACKAGE THERMAL CHARACTERISTICS (Note 2)
24 TQFN-EP
Junction-to-Ambient Thermal Resistance (θ
JA
) ............36°C/W
Junction-to-Case Thermal Resistance (θ
JC
) ................2.7°C/W
Note 2:
Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-
layer board. For detailed information on package thermal considerations, refer to
www.maxim-ic.com/thermal-tutorial.
ELECTRICAL CHARACTERISTICS
(V
AVDD
= V
DVDD
= 3.3V, T
A
= T
J
= -40°C to +85°C, V
RS+
- V
RS-
= 2V, V
RS-
= V
AGND
, unless otherwise stated.) (Note 3)
PARAMETER
GENERAL
AVDD/DVDD Operating Range
AVDD and DVDD Operating
Supply Current
AVDD UVLO
OUTPUT-VOLTAGE SENSING
MAX8688A, T
A
= 0°C to +85°C,
V
RS+
= 1V, V
RS-
= 0V
Voltage Regulation Accuracy (2V
Range, Table 8) (Note 4)
MAX8688A, T
A
= -40°C to +85°C,
V
RS+
= 1V, V
RS-
= 0V
MAX8688B, T
A
= 0°C to +85°C,
V
RS+
= 1V, V
RS-
= 0V
MAX8688B, T
A
= -40°C to +85°C,
V
RS+
= 1V, V
RS-
= 0V
MAX8688A, T
A
= 0°C to +85°C,
V
RS+
= 2.5V, V
RS-
= 0V
Voltage Regulation Accuracy (5.5V
range, Table 8) (Note 4)
MAX8688A, T
A
= -40°C to +85°C,
V
RS+
= 2.5V, V
RS-
= 0V
MAX8688B, T
A
= 0°C to +85°C,
V
RS+
= 2.5V, V
RS-
= 0V
MAX8688B, T
A
= -40°C to +85°C,
V
RS+
= 2.5V, V
RS-
= 0V
RS+, RS- Differential Mode Range
-0.2
-0.3
-0.4
-0.5
-0.3
-0.4
-0.4
-0.5
0
+0.2
+0.3
%
+0.4
+0.5
+0.3
+0.4
%
+0.4
+0.5
5.5
V
V
RS+
= V
RS-
= V
ISN+
= V
ISN-
= V
AGND
Rising
Hysteresis
2.70
3.0
6.7
2.8
100
3.6
8.5
2.95
V
mA
V
mV
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
2
_______________________________________________________________________________________
Digital Power-Supply Controller/Monitor
with PMBus Interface
ELECTRICAL CHARACTERISTICS (continued)
(V
AVDD
= V
DVDD
= 3.3V, T
A
= T
J
= -40°C to +85°C, V
RS+
- V
RS-
= 2V, V
RS-
= V
AGND
, unless otherwise stated.) (Note 3)
PARAMETER
RS- to AGND Differential Voltage
RS+ Input Bias Current
RS- Input Bias Current
OUTPUT CURRENT SENSE
V
ISN+
= 1V, V
ISN+
- V
ISN-
= 20mV,
T
A
= +25°C to +85°C
V
ISN+
= 1V, V
ISN+
- V
ISN-
= 20mV,
T
A
= -40°C to +85°C
ISN+, ISN- Common-Mode Range
ISN+, ISN- Common-Mode
Current-Sense Error
ISN+, ISN- Differential Mode
Range
ISN+, ISN- Input Bias Current
RS_C, ISN_C
RS_C, ISN_C Output Impedance
TEMPERATURE SENSING
Temperature Sensing Accuracy
CLKIO
CLKIO Input-Logic Low Voltage
CLKIO Input-Logic High Voltage
CLKIO Input Bias Current
CLKIO Input Clock Duty Cycle
CLKIO Output Low Voltage
CLKIO Output High Leakage
CLKIO Input/Output Clock Rise
Time
CLKIO Input/Output Clock Fall
Time
CLKIO Pullup Voltage
CLKIO Input Frequency
CLKIO Output Frequency
Accuracy
ENOUT,
FLT
OPEN-DRAIN LOGIC OUTPUTS
ENOUT,
FLT
Output Low Voltage
ENOUT,
FLT
Output High Leakage
ENOUT,
FLT
Pullup Voltage
I
SINK
= 4mA
V
ENOUT
= V
FLT
= 5.5V,
V
DVDD
= V
AVDD
= 3.6V
-1
0.4
+1
5.5
V
µA
V
f
EXT_CLK
100
0.95
1.00
V
CLKIO
= 0V or 3.6V
f
CLKIO
= 100kHz to 2500kHz
CLKIO in output mode, I
SINK
= 4mA
V
CLKIO
= V
DVDD
= V
AVDD
= 3.6V
R
PULLUP
= 560Ω, C
LOAD
= 20pF
R
PULLUP
= 560Ω, C
LOAD
= 20pF
-1
20
2
DVDD
2500
1.05
2.1
-1
20
+1
80
0.4
+1
0.8
V
V
µA
%
V
µA
ns
ns
V
kHz
MHz
Exposed pad = -40°C to +100°C
±3
°C
0.2
kΩ
V
ISN+
, V
ISN-
to V
AGND
= 0V or 5.5V
V
CM
= 0 to 5.5V, V
DM
= 20mV
-10
-20
-2.6
-7
0
0.9
+40
+40
+2.6
%
+7
5.5
V
%
mV
µA
2V range, V
RS+
= -0.25V to +2V
5.5V range, V
RS+
= -0.25V to +5.5V
2V or 5.5V range, V
RS-
= -0.25V to +0.25V
SYMBOL
CONDITIONS
MIN
-250
-10
-10
-10
TYP
MAX
+250
+15
+60
0
UNITS
mV
µA
µA
MAX8688
Current-Sense Accuracy (Note 4)
_______________________________________________________________________________________
3
Digital Power-Supply Controller/Monitor
with PMBus Interface
MAX8688
ELECTRICAL CHARACTERISTICS (continued)
(V
AVDD
= V
DVDD
= 3.3V, T
A
= T
J
= -40°C to +85°C, V
RS+
- V
RS-
= 2V, V
RS-
= V
AGND
, unless otherwise stated.) (Note 3)
PARAMETER
DAC
DAC Resolution
DAC Output-Voltage Range
DAC Output-Voltage Slew Rate
DAC Output Resistance
DAC Driving Capability
ADC
ADC Resolution
MAX8688A
MAX8688B
12
11
Bits
No load
12
REFO -
1 LSB
0.6
5
2
bits
V
V/µs
Ω
mA
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
THREE-STATE ADDRESS PINS (A3/ONOFF, A2/SDAE, A1/SCLE)
Three-State Address Pins Input
Low Voltage
Three-State Address Pins Input
Low Threshold Hysteresis
Three-State Address Pins Input
High Voltage
Three-State Address Pins Input
High Threshold Hysteresis
Three-State Address Pins Input
Bias Current
V
AVDD
= 3.6V, A3/ONOFF = A2/SDAE =
A1/SCLE = AVDD or AGND
-12
AVDD -
0.4
50
+12
50
0.3
V
mV
V
mV
µA
THREE-STATE ADDRESS PINS (A2/SDAE (DATA) AND A1/SCLE (CLOCK) WITH EEPROM) (Note 5)
A2/SDAE, A1/SCLE Output Low
Voltage
A2/SDAE, A1/SCLE Output High
Voltage
Output sink current = 100µA (Note 6)
Output source current = 100µA (Note 7)
0.7 x
AVDD
0.3 x
AVDD
V
V
THREE-STATE ADDRESS PIN (A3/ONOFF AS POL ON/OFF CONTROL)
Minimum A3/ONOFF Control Pulse
Low Time
Minimum A3/ONOFF Control Pulse
High Time
SCL, SDA SMBus™ SIGNALS
Maximum SMBus Speed
SCL, SDA Input Low Voltage
SCL, SDA Input High Voltage
SCL, SDA Output Low Voltage
SCL, SDA Input Leakage Per
Device Pin
V
SMB_IL
V
SMB_IH
V
SMB_OL
I
SMB_ILEAK
V
DVDD
= 3.0V to 3.6V
V
DVDD
= 3.0V to 3.6V
V
DVDD
= 3.0V to 3.6V at I
SINK
= 4mA
V
DVDD
= 3.6V, V
SCL
= V
SDA
= 0 or 3.6V
-1
2.1
100
0.8
DVDD
0.4
+1
kHz
V
V
V
µA
t
A3_LOW
t
A3_HIGH
250
750
µs
µs
SMBus is a trademark of Intel Corp.
4
_______________________________________________________________________________________
Digital Power-Supply Controller/Monitor
with PMBus Interface
ELECTRICAL CHARACTERISTICS (continued)
(V
AVDD
= V
DVDD
= 3.3V, T
A
= T
J
= -40°C to +85°C, V
RS+
- V
RS-
= 2V, V
RS-
= V
AGND
, unless otherwise stated.) (Note 3)
PARAMETER
RST
INPUT
RST
Input Low Voltage
RST
Input High Voltage
RST
Input Bias Current
Minimum SMBus Interface Reset
Pulse Width
SMBus Interface Recovery Time
After Interface Reset
Minimum Reset Pulse Width
Recovery Time After Device Reset
OTHER TIMING PARAMETERS
PMBus Command Response Time
Fault Response Time
t
PMB_RSP
t
FAULT_RSP
Overvoltage fault
Overcurrent fault
300
5
5
µs
ms
t
SMB_RST
t
SMB_WAIT
t
RST
t
RST_WAIT
565
15
V
RST_IL
V
RST_IH
V
DVDD
= 3.0V to 3.6V
V
DVDD
= 3.0V to 3.6V
RST
= DVDD or DGND
1
15
2.1
10
455
0.8
V
V
µA
µs
µs
µs
µs
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
MAX8688
Note 3:
Production tested at T
A
= +25°C and T
A
= +85°C. Specifications from T
A
= -40°C to +25°C are guaranteed by design,
unless otherwise noted.
Note 4:
Production tested at T
A
= +85°C only. All other temperatures are guaranteed by design.
Note 5:
When an EEPROM is connected to A2/SDAE and A1/SCLE, these pins cannot be hardwired to ground or supply. They must
be connected through 33kΩ ±5% resistors.
Note 6:
Equivalent of having 33kΩ pulldown resistor to DGND.
Note 7:
Equivalent of having 33kΩ pullup resistor to DVDD.
Typical Operating Characteristics
(V
AVDD
= V
DVDD
= 3.3V, T
A
= +25°C, unless otherwise noted.)
REFIN MODE SOFT-START
WITH TRACKING
MAX8688 toc01
REFIN MODE SOFT-STOP
WITH TRACKING
MAX8688 toc02
V
OUT_4
= 1.8V
V
OUT_3
= 1.5V
V
OUT_2
= 1.2V
V
OUT_1
= 1.0V
0.5V/div
V
OUT_4
= 1.8V
V
OUT_3
= 1.5V
V
OUT_2
= 1.2V
V
OUT_1
= 1.0V
0.5V/div
2ms/div
2ms/div
_______________________________________________________________________________________
5
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