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MAX17491

Single-Phase Synchronous MOSFET Driver

________________________________________________________________

Maxim Integrated Products

19-5324; Rev 0; 6/10

EVALUATION KIT

AVAILABLE

SKIP

PWM

BST

GND

TQFN

MAX17491

TOP VIEW

Pin Configuration

MAX17491

PWM

BST

GND

PAD

PWM

+5V BIAS

SUPPLY

SKIP

INPUT (V

)

5V TO 24V

OUT

(1.45V

AT 20A)

Typical Operating Circuit

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.

General Description

The MAX17491 is a single-phase synchronous nonin-

verting MOSFET driver. The MAX17491 is intended to

work with controller ICs like the MAX8736, MAX8786, or

MAX17030 in multiphase notebook CPU core regulators.

The regulators can either step down directly from the

battery voltage to create the core voltage or step down

from the main system supply. The single-stage conver-

sion method allows the highest possible efficiency, while

the 2-stage conversion at higher switching frequency

provides the minimum possible physical size.

The low-side driver is optimized to drive 3nF capacitive

loads with 4ns/8ns typical fall/rise times, and the high-

side driver with 8ns/10ns typical fall/rise times.

Adaptive dead-time control prevents shoot-through cur-

rents and maximizes converter efficiency.

The MAX17491 features improved zero crossing and

UVLO performance over the MAX8791/MAX8791B.

The MAX17491 is available in a small, lead-free, 8-pin,

3mm x 3mm TQFN package.

Applications

Notebooks/Desktops/Servers

CPU Core Power Supplies

Multiphase Step-Down Converters

Features

♦ Single-Phase Synchronous MOSFET Driver

♦ 0.5Ω Low-Side On-Resistance

♦ 0.7Ω High-Side On-Resistance

♦ 10ns Minimum Guaranteed Dead Time

♦ Integrated Boost “Diode”

♦ 2V to 24V Input Voltage Range

♦ Selectable Pulse-Skipping Mode

♦ Low-Profile, 3mm x 3mm, TQFN Package

Ordering Information

Denotes a lead(Pb)-free/RoHS-compliant package.

EP = Exposed pad.

PART TEMP RANGE PIN-PACKAGE

MAX17491GTA+ -40°C to +105°C 8 TQFN-EP*

Summary of content (12 pages)

PAGE 1
9-5324; Rev 0; 6/10 KIT ATION EVALU E L B AVAILA Single-Phase Synchronous MOSFET Driver Features The MAX17491 is a single-phase synchronous noninverting MOSFET driver. The MAX17491 is intended to work with controller ICs like the MAX8736, MAX8786, or MAX17030 in multiphase notebook CPU core regulators. The regulators can either step down directly from the battery voltage to create the core voltage or step down from the main system supply.
PAGE 2
MAX17491 Single-Phase Synchronous MOSFET Driver ABSOLUTE MAXIMUM RATINGS VDD to GND...............…………………….………….. -0.3V to +6V SKIP to GND..................………………………………-0.3V to +6V PWM to GND ................……………………………….-0.3V to +6V DL to GND ..................................................-0.3V to (VDD + 0.3V) BST to GND ............................................................-0.3V to +36V DH to LX ....................................................-0.3V to (VBST + 0.3V) BST to VDD ...............
PAGE 3
Single-Phase Synchronous MOSFET Driver (Circuit of Figure 1, VDD = VSKIP = 5V, TA = -40°C to +105°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER SYMBOL DL Driver Sink Current Zero-Crossing Threshold Boost On-Resistance CONDITIONS IDL_SINK MIN DL forced to 2.5V GND - LX, SKIP = GND VZX R ON(BST) VDD = 5V, DH = LX = GND (pulldown state), IBST = 10mA PWM Input Levels TYP High (DH = high, DL = low) Midlevel VDD/2 0.
PAGE 4
Typical Operating Characteristics (continued) (Circuit of Figure 1, VDD = 5V, CDH = 3nF, CDL = 3nF, TA = +25°C, unless otherwise noted.) DH AND DL RISE AND FALL TIMES vs. TEMPERATURE 25 20 FALL TIME 15 10 35 A 30 40 DH RISE 25 DH FALL 20 20 DL IS DRIVING 2 SI7336ADP DH IS DRIVING 1 SI7892ADP CDL = CDH 10 0 1000 2500 4000 5500 7000 CAPACITANCE (pF) -40 8500 10,000 -15 A: CDH = 3.3nF, CDL = 3.3nF B: CDH = 1.5nF, CDL = 6.
PAGE 5
Single-Phase Synchronous MOSFET Driver (Circuit of Figure 1, VDD = 5V, CDH = 3nF, CDL = 3nF, TA = +25°C, unless otherwise noted.) SWITCHING WAVEFORMS (PWM = HIGH TO MID TO HIGH) SWITCHING WAVEFORMS (PWM = MID TO LOW TO MID) MAX17491 toc12 MAX17491 toc11 5V 5V/div 0 VPWM VDL 5V 5V/div 0 VLX 0 10V/div VDH 0 10V/div VPWM VDL VLX 5V 5V/div 0 0 5V/div 10V 10V/div 0 15V VDH 10V/div 0 Pin Description PIN NAME FUNCTION 1 BST Boost Flying-Capacitor Connection.
PAGE 6
MAX17491 Single-Phase Synchronous MOSFET Driver PWM DH BST PWM SKIP SKIP MAX17491 LX DL +5V BIAS SUPPLY VDD CDH 3nF CBST 0.1μF CDL 3nF GND C1 1.0μF PAD Figure 1. Test Circuit tPWM-DH tPWM-DL tMID tPWM-DL tMID PWM tF_DL tR_DL tF_DL tR_DL DL tDH-DL tDL-DH DH tR_DH tR_DH tR_DH tR_DH tPWM-DH Figure 2.
PAGE 7
Single-Phase Synchronous MOSFET Driver MAX17491 INPUT (VIN) CIN PWM SKIP PWM DH SKIP BST MAX17491 +5V BIAS SUPPLY NH 2x 10μF L1 0.36μH CBST 0.22μF LX OUTPUT (VOUT) COUT 2x 330μF 6mΩ VDD CVDD 1.0μF DL NL DL GND PAD Figure 3. Typical MOSFET-Driver Application Circuit Table 1.
PAGE 8
MAX17491 Single-Phase Synchronous MOSFET Driver VDD BST PWM DRV DH DRIVER LOGIC AND DEAD-TIME CONTROL THERMAL SHUTDOWN LX UVLO DRV# VDD SKIP DL LX GND ZX DETECTION PAD Figure 4. Overview Block Diagram Adaptive Shoot-Through Protection The DH and DL drivers are optimized for driving moderately sized high-side and larger low-side power MOSFETs. This is consistent with the low duty factor seen in the notebook CPU environment, where a large VIN - VOUT differential exists.
PAGE 9
Single-Phase Synchronous MOSFET Driver Input Undervoltage Lockout When VDD is below the UVLO threshold, DH and DL are held low. Once VDD is above the UVLO threshold and while PWM is low, DL is driven high and DH is driven low. This prevents the output of the converter from rising before a valid PWM signal is applied. Low-Power Pulse Skipping The MAX17491 enters into low-power pulse-skipping mode when SKIP is pulled low.
PAGE 10
MAX17491 Single-Phase Synchronous MOSFET Driver Switching losses in the high-side MOSFET can become an insidious heat problem when maximum AC adapter voltages are applied due to the squared term in the switching-loss equation above. If the high-side MOSFET chosen for adequate RDS(ON) at low battery voltages becomes extraordinarily hot when biased from VIN(MAX), consider choosing another MOSFET with lower parasitic capacitance.
PAGE 11
Single-Phase Synchronous MOSFET Driver PROCESS: BiCMOS For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. Note that a “+”, “#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status. PACKAGE TYPE PACKAGE CODE OUTLINE NO. LAND PATTERN NO.
PAGE 12
MAX17491 Single-Phase Synchronous MOSFET Driver Revision History REVISION NUMBER REVISION DATE 0 6/10 DESCRIPTION Initial release PAGES CHANGED — 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.