MAX8686ETL+T Datasheet MAX8686ETL+, MAX8686ETL+T, MAX8686EVKIT+ | P7-P9

PHASE SHEDDING FROM 6 PHASES

TO 2 PHASES (I

OUT

= 30A)

MAX8686 toc18

s/div

2V/div

LX1

10V/div

LX5

10V/div

LX2

10V/div

CIRCUIT OF FIGURE 4

MAX8686

Single/Multiphase, Step-Down,

DC-DC Converter Delivers Up to 25A Per Phase

_______________________________________________________________________________________ 7

PHASE RECOVERY FROM 2 PHASES

TO 6 PHASES (I

OUT

= 30A)

MAX8686 toc19

s/div

2V/div

LX1

10V/div

LX5

10V/div

LX2

10V/div

CIRCUIT OF FIGURE 4

SAFE OPERATING AREA

MAX8686 toc20

AMBIENT TEMPERATURE (°C)

OUT

(A)

807565 7035 40 45 50 55 6030

25 85

400 LFM

300 LFM

200 LFM

100 LFM

0 LFM

= +125°C, V

OUT

= 1.2V

SAFE OPERATING AREA

MAX8686 toc21

AMBIENT TEMPERATURE (°C)

OUT

(A)

807565 7035 40 45 50 55 6030

25 85

400 LFM

300 LFM

200 LFM

100 LFM

0 LFM

= +125°C, V

OUT

= 3.3V

LX_ SWITCHING WAVEFORM FOR

PHASES 4, 5, 6, AND 1

MAX8686 toc16

200ns/div

LX4

5V/div

LX5

5V/div

LX6

5V/div

LX1

5V/div

CIRCUIT OF FIGURE 4

REFO OUTPUT vs. TEMPERATURE

MAX8686 toc17

TEMPERATURE (

REFO OUTPUT (V)

80706050403020100-10-20-30

3.28

3.29

3.30

3.31

3.32

3.33

3.27

-40 90

Typical Operating Characteristics (continued)

= 12V, f

= 500kHz, single phase, circuit of Figure 2, unless otherwise noted.)

MAX8686

Single/Multiphase, Step-Down,

DC-DC Converter Delivers Up to 25A Per Phase

8 _______________________________________________________________________________________

Pin Description

PIN NAME FUNCTION

1 CS-

Negative Differential Current-Sense Input. Connect CS- to the output side of the inductor for lossless

current sense or to the load side of the current-sense resistor.

2 CS+

Positive Differential Current-Sense Input. Connect CS+ to the inductor through an RC network for

lossless current sense or to the inductor side of the current-sense resistor.

3 GFREQ

FREQ

Capacitor Return Terminal. Connect the frequency-setting capacitor C

FREQ

to GFREQ as close

as possible to the device.

4 EN/SLOPE

Enable and Slope Compensation Input. Connect a resistor from EN/SLOPE to GND to set the desired

slope compensation ramp voltage. An internal 10μA current source pulls up EN/SLOPE. The device

shuts down when the voltage at EN/SLOPE is less than 0.7V. Connect EN/SLOPE to an open-drain or

open-collector output for system enable or phase-shedding function.

5, 16 LX Inductor Connection. LX is high impedance during shutdown.

6 RTN

Power Ground for Low-Side Gate Driver. Connect RTN to PGND plane at the return terminal of the IN

bypass capacitor.

7–15 PGND Power Ground. Low-side MOSFET source connection.

17 N.C. No Connection. Not internally connected.

18–26 IN

Power Input. Connect IN to the input voltage source. Connect input bypass capacitor from IN to PGND

as close as possible to the device. Connect IN, INA, and VL together for 5V operation (see Figure 3).

27 INA Input of the Internal VL Linear Regulator. Bypass INA with a 0.1μF capacitor to PGND.

28 GND Analog Ground

29 AVL Input Voltage to the Device’s Internal Analog Circuitry. Connect AVL to VL through a lowpass RC filter.

30 VL

Internal 5.4V Linear Regulator Output. Connect a ceramic capacitor of at least 1μF from VL to RTN. INA

is the input to this linear regulator. Connect VL to INA when V

INA

is less than 5.5V. VL provides power

for the MOSFET drivers.

31 BST Boost Capacitor Connection. Connect a 0.22μF ceramic capacitor from BST to LX.

32 POK

Power-Good Output. POK is an open-drain output that is high impedance when the output voltage is at

its nominal regulated voltage. The POK rising threshold is 90% of the reference voltage at REFIN. POK

is internally pulled low during shutdown. Connect POK to GND for slave mode operation.

MAX8686

Single/Multiphase, Step-Down,

DC-DC Converter Delivers Up to 25A Per Phase

_______________________________________________________________________________________ 9

Pin Description (continued)

PIN NAME FUNCTION

33 FREQ

Frequency-Setting Input. Connect a capacitor from FREQ to GFREQ to set the switching frequency.

The triangle ramp runs between 0 and AVL/2. In multiphase applications, connect FREQ of the master

and all slave devices together. FREQ is internally pulled to GFREQ during shutdown.

34 SS

Soft-Start Input. For master-mode or single-phase operation, connect a capacitor from SS to GND to

set the soft-start time. A 25μA internal current source charges the capacitor. SS is pulled to GND in

shutdown. Connect SS to GND for slave mode operation.

35 ILIM

Analog Programmable Current Limit. Connect a resistor from ILIM to GND to set the current limit. A

10μA current source through this resistor sets the current-limit threshold. In multiphase applications,

connect ILIM of the master and all slave devices together.

36 REFIN

Voltage Error-Amplifier Reference Input. For master-mode or single-phase operation, connect REFIN to

PHASE/REFO through a resistor-divider to set the output voltage from 0 to 3.3V. To use an external

reference, connect REFIN to the system reference voltage, and use an RC network at REFIN to

implement soft-start if the external reference does not provide this function. Connect REFIN to GND for

slave mode operation.

37 P H AS E /RE FO

Phase Selection Input/Reference Voltage Output. For single-phase or master-mode operation, the 3.3V

output with 1% accuracy can be used as a reference voltage. For multiphase operation, connect

PHASE/REFO of each slave device to the center tap of a resistor-divider from the master AVL to GND.

The resistor values are selected to set phase delay between phases. The PWM cycle starts 60ns after

the rising edge of V

FREQ

crosses V

PHASE

38 COMP

Compensation and Output of the Voltage-Error Amplifier. Connect a Type II compensation network at

COMP. COMP is internally pulled to GND in shutdown. In multiphase applications, connect COMP of

the master and all slave devices together.

39 RS+

Positive Input of the Output-Voltage Remote Sense. For master-mode or single-phase operation,

connect RS+ to the output-voltage sense point at the load. Connect RS+ to AVL (slave) for slave mode

operation.

40 RS-

Negative Input of the Output-Voltage Remote Sense. For master-mode or single-phase operation,

connect RS- to the remote ground at the load. Connect RS- to AVL (slave) for slave mode operation.

— GND_EP Ground Exposed Paddle. Connect GND_EP to GND.

— IN_EP Input Exposed Paddle. Connect IN_EP to IN.

— LX_EP LX Exposed Paddle. Connect LX_EP to LX.

P1-P3 P4-P6 P7-P9 P10-P12 P13-P15 P16-P18 P19-P21 P22-P23

MAX8686ETL+T

Mfr. #:

Buy MAX8686ETL+T

Manufacturer:

Maxim Integrated

Description:

Switching Voltage Regulators Multiphase Step-Down DC/DC Converter

Lifecycle:

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MAX8686ETL+T

MAX8686ETL+T

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