IC BUCK SYNC ADJ 25A 40TQFN

MAX8686ETL+

Manufacturer Part NumberMAX8686ETL+
DescriptionIC BUCK SYNC ADJ 25A 40TQFN
ManufacturerMaxim Integrated Products
TypeStep-Down (Buck)
MAX8686ETL+ datasheet
 


Specifications of MAX8686ETL+

Internal Switch(s)YesSynchronous RectifierYes
Number Of Outputs1Voltage - Output0.7 ~ 5.5 V
Current - Output25AFrequency - Switching300kHz ~ 1MHz
Voltage - Input4.5 ~ 20 VOperating Temperature-40°C ~ 85°C
Mounting TypeSurface MountPackage / Case40-TQFN Exposed Pad
Power - Output4WLead Free Status / RoHS StatusLead free / RoHS Compliant
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19-4113; Rev 1; 10/10
DC-DC Converter Delivers Up to 25A Per Phase
General Description
The MAX8686 current-mode, synchronous PWM step-
down regulator with integrated MOSFETs operates from
a 4.5V to 20V input supply and generates an adjustable
output voltage from 0.7V to 5.5V while delivering up to
25A per phase.
The MAX8686 employs a peak current-mode architec-
ture that operates with an adjustable switching frequency
from 300kHz to 1MHz. An adjustable current-limit thresh-
old allows for optimization for different applications with
different load currents. Inductor current sense is
achieved either using an external sense resistor or using
a lossless inductor current-sense scheme. The foldback
and hiccup current limit reduces the power dissipation
during overload or short-circuit conditions and allows for
autorecovery when the fault condition is removed.
The MAX8686 offers the ability to start up monotonically
even when there is a prebias output voltage. In addi-
tion, an adjustable soft-start capability allows for a con-
trolled turn-on. The MAX8686 features an accurate 1%
reference and offers a reference input that allows for a
higher accuracy reference to be used for voltage track-
ing applications such as DDR memory.
The MAX8686 can be paralleled (up to eight) together
in a true multiphase mode to deliver up to 200A of out-
put current. When operating in this mode, this device
achieves better than 10% current balance between
phases at full load. The MAX8686 supports program-
mable phase shedding to improve system efficiency
during light load conditions.
Other features include an enable input and a power-OK
(POK) indicator used for power sequencing. The
MAX8686 also features latch overvoltage protection
that turns on the low-side MOSFET when the output
voltage exceeds 120% of the nominal voltage. The
MAX8686 is offered in a thermally enhanced 40-pin,
6mm x 6mm TQFN package.
POL Power Supplies
Module Replacements
Telecom Equipment
Networking Equipment
Servers
DDR Memory
Pin Configuration appears at end of data sheet.
________________________________________________________________ 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.
Single/Multiphase, Step-Down,
o Operating Range from 4.5V to 20V Input Supply
o 1% Reference Voltage Accuracy Over Temperature
o Reference Input (REFIN) for Output Tracking or
System Reference Voltage
o Adjustable Switching Frequency from 300kHz
to 1MHz
o Single/Multiphase Operation Delivers Up to
25A/200A with Integrated MOSFETs
o Adjustable Current Limit
o Monotonic Output Voltage at Startup (Prebias)
o Output Sink and Source Current Capability
o Adjustable Soft-Start
o Thermal-Overload Protection
o Output Overvoltage Protection
o Thermally Enhanced 6mm x 6mm TQFN
Package (4W)
PART
MAX8686ETL+
+ Denotes a lead-free package.
* EP = Exposed pad.
V
= 12V
IN
Applications
ENABLE
INPUT
Features
Ordering Information
TEMP RANGE
PIN-PACKAGE
-40°C to +85°C
40 TQFN-EP*
Typical Application Circuit
IN
BST
V
OUT
PGND
LX
RS+
REFIN
MAX8686
RS-
CS+
PHASE/REFO
CS-
COMP
POK
EN/SLOPE
FREQ
SS GND
ILIM
= 1.2V/25A
POK
OUTPUT
1

MAX8686ETL+ Summary of contents

  • Page 1

    ... Integrated MOSFETs o Adjustable Current Limit o Monotonic Output Voltage at Startup (Prebias) o Output Sink and Source Current Capability o Adjustable Soft-Start o Thermal-Overload Protection o Output Overvoltage Protection o Thermally Enhanced 6mm x 6mm TQFN Package (4W) PART MAX8686ETL+ + Denotes a lead-free package Exposed pad 12V IN Applications ENABLE INPUT Features ...

  • Page 2

    Single/Multiphase, Step-Down, DC-DC Converter Delivers Up to 25A Per Phase ABSOLUTE MAXIMUM RATINGS IN, INA to PGND.....................................................-0.3V to +22V BST LX...........................................................-0.3V to +6V BST to PGND..........................................................-0.3V to +28V LX to PGND...........................-0. BST to VL................................................................-0.3V to +22V ...

  • Page 3

    DC-DC Converter Delivers Up to 25A Per Phase ELECTRICAL CHARACTERISTICS (continued 12V AVL 1V INA REFIN C = 0.22μ 270pF +25°C, unless otherwise noted.) (Note 2) ...

  • Page 4

    Single/Multiphase, Step-Down, DC-DC Converter Delivers Up to 25A Per Phase ELECTRICAL CHARACTERISTICS (continued 12V AVL 1V INA REFIN C = 0.22μ 270pF +25°C, unless otherwise noted.) ...

  • Page 5

    DC-DC Converter Delivers Up to 25A Per Phase (V = 12V 500kHz, single phase, circuit of Figure 2, unless otherwise noted SINGLE-PHASE EFFICIENCY vs. LOAD CURRENT 95 3.3V OUT 92.5 90.0 87.5 85.0 V ...

  • Page 6

    Single/Multiphase, Step-Down, DC-DC Converter Delivers Up to 25A Per Phase (V = 12V 500kHz, single phase, circuit of Figure 2, unless otherwise noted SOFT-START WITH EN CONTROL (I = 10A) OUT MAX8686 toc10 EN 2V/div SS ...

  • Page 7

    DC-DC Converter Delivers Up to 25A Per Phase (V = 12V 500kHz, single phase, circuit of Figure 2, unless otherwise noted LX_ SWITCHING WAVEFORM FOR PHASES AND 1 CIRCUIT OF FIGURE 4 LX4 ...

  • Page 8

    Single/Multiphase, Step-Down, DC-DC Converter Delivers Up to 25A Per Phase PIN NAME Negative Differential Current-Sense Input. Connect CS- to the output side of the inductor for lossless 1 CS- current sense or to the load side of the current-sense resistor. ...

  • Page 9

    DC-DC Converter Delivers Up to 25A Per Phase PIN NAME Frequency-Setting Input. Connect a capacitor from FREQ to GFREQ to set the switching frequency. 33 FREQ The triangle ramp runs between 0 and AVL/2. In multiphase applications, connect FREQ of ...

  • Page 10

    Single/Multiphase, Step-Down, DC-DC Converter Delivers Up to 25A Per Phase INA 10μA EN/SLOPE 5.4V LDO GENERATOR VL AVL VOLTAGE REFERENCE SS SLAVE MODE = S1, S2, S3, S5, S6 OPEN MASTER MODE = S1, S2, S5, S6 CLOSE SLAVE MODE ...

  • Page 11

    DC-DC Converter Delivers Up to 25A Per Phase Detailed Description DC-DC Converter Control Architecture The MAX8686 step-down regulator uses a PWM, cur- rent-mode control scheme. An internal transconduc- tance amplifier establishes an integrated error voltage. The heart of the PWM ...

  • Page 12

    Single/Multiphase, Step-Down, DC-DC Converter Delivers Up to 25A Per Phase For using an external reference on REFIN, SS needs to be tied to REFIN either directly or indirectly through a resistor for soft-start. For REFIN voltage lower than 1.25V, connect ...

  • Page 13

    DC-DC Converter Delivers Up to 25A Per Phase Current-Limit Circuit The current-limit threshold is set by a resistor between ILIM and GND. Under soft-overload conditions, when the peak inductor current exceeds the selected current limit, the high-side MOSFET is turned ...

  • Page 14

    Single/Multiphase, Step-Down, DC-DC Converter Delivers Up to 25A Per Phase Overvoltage Protection The MAX8686 provides output overvoltage protection (OVP). The OVP threshold is set at 20% above the set output voltage. When the overvoltage condition is expe- rienced, the output ...

  • Page 15

    DC-DC Converter Delivers Up to 25A Per Phase C16 0.22μF C17 R13 1μF 10Ω R1 C18 10kΩ 0.22μF 31 BST LX 32 POWER- POK OK C1 330pF GFREQ 33 FREQ C2 C3 15pF 10nF 130kΩ 35 ILIM ...

  • Page 16

    Single/Multiphase, Step-Down, DC-DC Converter Delivers Up to 25A Per Phase INA 27 GND 28 AVL ...

  • Page 17

    DC-DC Converter Delivers Up to 25A Per Phase Design Procedures Setting the Output Voltage To set the output voltage for the MAX8686, connect REFIN to the center of an external resistor-divider from PHASE/REFO to GND (R3 and R4 of Figures ...

  • Page 18

    Single/Multiphase, Step-Down, DC-DC Converter Delivers Up to 25A Per Phase Setting the Peak Current Limit The peak current-limit threshold (V a resistor connected from ILIM to GND. An internal 10µA current source flows through this resistor to set a voltage ...

  • Page 19

    DC-DC Converter Delivers Up to 25A Per Phase ripple-current requirement (I RMS switching currents as defined by the following equations: = × × RMS OUT MAX _ for ( ≤ × × ...

  • Page 20

    Single/Multiphase, Step-Down, DC-DC Converter Delivers Up to 25A Per Phase resistor, and compensation capacitors determine the loop stability. The inductor and output capacitor are chosen based on performance, size, and cost. Additionally, the compensation resistor and capacitors are selected to ...

  • Page 21

    DC-DC Converter Delivers Up to 25A Per Phase be less than or equal to 1/5 the switching frequency. Select a value for f in the range << ≤ pMOD C The feedback voltage-divider gain (V ...

  • Page 22

    Single/Multiphase, Step-Down, DC-DC Converter Delivers Up to 25A Per Phase Applications Information PCB Layout Guidelines Careful PCB layout is critical to achieve low switching losses and clean, stable operation. The switching power stage requires particular attention. Follow these guidelines for ...

  • Page 23

    ... Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 23 © 2010 Maxim Integrated Products ...