Datasheet

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General Description

The MAX5088/MAX5089 high-frequency, DC-DC con-

verters with an integrated n-channel power MOSFET

provide up to 2A of load current. The MAX5088

includes an internal power MOSFET to enable the

design of a nonsynchronous buck topology power sup-

ply. The MAX5089 is for the design of a synchronous

buck topology power supply. These devices operate

from a 4.5V to 5.5V or 5.5V to 23V input voltage and a

200kHz to 2.2MHz resistor-programmable switching

frequency. The voltage-mode architecture with a peak

switch current-limit scheme provides stable operation

up to a 2.2MHz switching frequency. The MAX5088

includes a clock output for driving a second DC-DC

converter 180° out-of-phase and a power-on-reset

(RESET) output. The MAX5089 includes a power-good

output and a synchronous rectifier driver to drive an

external low-side MOSFET in the buck converter config-

uration for high efficiency.

The MAX5088/MAX5089 protect against overcurrent

conditions by utilizing a peak current limit as well as

overtemperature shutdown providing a very reliable

and compact power source for point-of-load regulation

applications. Additional features include synchroniza-

tion, internal digital soft-start, and an enable input. The

MAX5088/MAX5089 are available in a thermally

enhanced, space-saving 16-pin TQFN (5mm x 5mm)

package and operate over the -40°C to +125°C tem-

perature range.

Applications

xDSL Modem Power Supply

Automotive Radio Power Supply

Servers and Networks

IP Phones/WLAN Access Points

Features

♦ 4.5V to 5.5V or 5.5V to 23V Input Voltage Range

♦ Output Voltage Adjustable Down to 0.6V

♦ 2A Output Current

♦ Synchronous Rectifier Driver Output (MAX5089)

for Higher Efficiency

♦ Resistor-Programmable Switching Frequency

from 200kHz to 2.2MHz

♦ External Synchronization and Enable (On/Off)

Inputs

♦ Clock Output for Driving Second Converter 180°

Out-Of-Phase (MAX5089)

♦ Integrated 150mΩ High-Side n-Channel Power

MOSFET

♦ Power-On Reset Output (MAX5088)/Power-Good

Output (MAX5089)

♦ Short-Circuit Protection

♦ Thermal-Shutdown Protection

♦ Thermally Enhanced 16-Pin TQFN Package

Dissipates 2.7W

MAX5088/MAX5089

2.2MHz, 2A Buck Converters with an

Integrated High-Side Switch

________________________________________________________________ Maxim Integrated Products 1

DRAIN

PGND

CKO

SOURCE

RESET

12 11 9

BST/VDD

V+

BYPASS

OSC

MAX5088

COMP SGND

SYNC

EP*

*EXPOSED PAD.

THIN QFN

5mm x 5mm

TOP VIEW

Pin Configurations

Ordering Information

19-3944; Rev 1; 5/06

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at

1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

Pin Configurations continued at end of data sheet.

EVALUATION KIT

AVAILABLE

PART

TEMP RANGE

PIN-

PACKAGE

PKG

CODE

MAX5088ATE+

-40°C to +125°C

16 TQFN

T1655-2

MAX5089ATE+

-40°C to +125°C

16 TQFN

T1655-2

Selector Guide

PART

CONFIGURATION

FEATURES

MAX5088ATE

Nonsynchronous

Buck

RESET Output,

Clock Output

MAX5089ATE

Synchronous Buck

PGOOD Output,

Synchronous FET

Driver

+Denotes lead-free package.

Summary of content (24 pages)

PAGE 1
9-3944; Rev 1; 5/06 KIT ATION EVALU LE B A IL A AV 2.2MHz, 2A Buck Converters with an Integrated High-Side Switch The MAX5088/MAX5089 high-frequency, DC-DC converters with an integrated n-channel power MOSFET provide up to 2A of load current. The MAX5088 includes an internal power MOSFET to enable the design of a nonsynchronous buck topology power supply. The MAX5089 is for the design of a synchronous buck topology power supply. These devices operate from a 4.5V to 5.5V or 5.
PAGE 2
MAX5088/MAX5089 2.2MHz, 2A Buck Converters with an Integrated High-Side Switch ABSOLUTE MAXIMUM RATINGS RESET, PGOOD to SGND ........................................-0.3V to +6V BYPASS to SGND..................................................-0.3V to +2.2V VL and BYPASS Short-Circuit Duration to SGND ......Continuous Continuous Power Dissipation* (TA = +70°C) 16-Pin TQFN (derate 33mW/°C above +70°C) ..........2666mW Package Thermal Resistance (junction to case) ............1.
PAGE 3
2.2MHz, 2A Buck Converters with an Integrated High-Side Switch (V+ = VL = 5V or V+ = 5.5V to 23V, VEN = 5V, TA = TJ = -40°C to +125°C, unless otherwise noted. Circuits of Figures 5 and 6. Typical values are at TA = TJ = +25°C.
PAGE 4
MAX5088/MAX5089 2.2MHz, 2A Buck Converters with an Integrated High-Side Switch ELECTRICAL CHARACTERISTICS (continued) (V+ = VL = 5V or V+ = 5.5V to 23V, VEN = 5V, TA = TJ = -40°C to +125°C, unless otherwise noted. Circuits of Figures 5 and 6. Typical values are at TA = TJ = +25°C.) (Note 1) PARAMETER SYNC Frequency Range (Note 3) SYMBOL CONDITIONS fSYNC MIN TYP 200 MAX UNITS 2200 kHz Sync Input to SOURCE RisingEdge Phase Delay (Note 4) SYNCPHASE ROSC = 10kΩ, fSYNC = 1.
PAGE 5
2.2MHz, 2A Buck Converters with an Integrated High-Side Switch MAX5088 BUCK EFFICIENCY vs. OUTPUT CURRENT (VIN = 12V, fSW = 2.2MHz) 70 60 50 40 30 20 10 2.5V 50 EFFICIENCY (%) 60 50 40 30 40 30 20 20 10 10 0 0 500 1000 1500 2000 0 0 2500 500 1000 1500 0 500 OUTPUT CURRENT (mA) OUTPUT CURRENT (mA) 90 3.3V 80 2.5V 75 70 80 75 1.2V 3.3V 70 EFFICIENCY (%) 85 1500 2000 2500 MAX5089 SYNCHRONOUS EFFICIENCY vs. OUTPUT CURRENT (VIN = 12V, fSW = 2.2MHz, L = 4.
PAGE 6
Typical Operating Characteristics (continued) (V+ = VL = 5.2V, TA = +25°C, Figures 5 and 6, unless otherwise noted.) FREQUENCY (kHz) V+ = 5.25V 0.250 0.200 V+ = 5V 0.150 2100 1000 1600 1350 850 0.050 350 1100 1600 0 2100 ROSC = 20kΩ ROSC = 40kΩ 100 100 600 ROSC = 10kΩ 1100 600 100 ROSC = 6.04kΩ 1850 0.100 0 10 20 30 40 50 60 70 -40 10 60 TEMPERATURE (°C) RESISTANCE (kΩ) SWITCHING FREQUENCY (kHz) MAX5089 LOAD-TRANSIENT RESPONSE (IOUT = 0.
PAGE 7
2.2MHz, 2A Buck Converters with an Integrated High-Side Switch MAX5089 SOFT-START AND SHUTDOWN (IOUT = 2A) VIN STARTUP WAVEFORM (EN CONNECTED TO VL) MAX5088/89 toc15 RESET TIMEOUT MAX5088/89 toc17 MAX5088/89 toc16 VEN 5V/div VIN = 12V VIN 10V/div VOUT 2V/div 1V/div VOUT VEN VPGOOD 5V/div 0V 5V/div VEN 5V/div VOUT 2V/div 5V/div VRESET 0V VIN 10V/div 1ms/div 40ms/div 1ms/div SHUTDOWN CURRENT vs.
PAGE 8
2.2MHz, 2A Buck Converters with an Integrated High-Side Switch MAX5088/MAX5089 Pin Description PIN NAME 1, 2 DRAIN Internal Power MOSFET Drain Connection. Use the MOSFET as a high-side switch and connect DRAIN to the input supply. 3 COMP Transconductance Error Amplifier Output. Connect a compensation network from COMP to SGND or from COMP to FB to SGND (see the Compensation section). 4 FB 5 OSC 6 BYPASS 7 V+ Input Supply Voltage. V+ can range from 5.5V to 23V.
PAGE 9
2.2MHz, 2A Buck Converters with an Integrated High-Side Switch MAX5088/MAX5089 V+ DRAIN VL LDO VL = 5.2V SYNC RSENSE CKO OSCILLATOR OSC 4-PULSE SKIP BST/VDD 2V R 200mΩ 1V Q N2 BYPASS SOURCE Q ADAPTIVE BBM VREF 30Ω N3 fSW / 4 PGND EN DIGITAL SOFT-START gm VREF = 0.6V FB COMP SGND 200mV RESET MAX5088 0.92 x VREF N1 180ms DELAY Figure 1.
PAGE 10
MAX5088/MAX5089 2.2MHz, 2A Buck Converters with an Integrated High-Side Switch V+ DRAIN VL LDO VL = 5.2V SYNC RSENSE OSCILLATOR OSC 4-PULSE SKIP BST/VDD 2V R 200mΩ 1V Q N2 BYPASS SOURCE Q ADAPTIVE BBM 30Ω N3 fSW / 4 VL VREF DL PGND EN DIGITAL SOFT-START gm VREF = 0.6V FB COMP SGND 200mV PGOOD MAX5089 0.92 x VREF Figure 2.
PAGE 11
2.2MHz, 2A Buck Converters with an Integrated High-Side Switch PWM Controller The MAX5088/MAX5089 use a pulse-width modulation (PWM) voltage-mode control scheme. The MAX5088 is a nonsynchronous converter and uses an external lowforward-drop Schottky diode for rectification. The MAX5089 is a synchronous converter and drives a lowside, low-gate-charge MOSFET for higher efficiency. The controller generates the clock signal from an internal oscillator or the SYNC input when driven by an external clock.
PAGE 12
MAX5088/MAX5089 2.2MHz, 2A Buck Converters with an Integrated High-Side Switch Enable EN is an active-high input that turns the MAX5088/ MAX5089 on and off. EN is a TTL logic input with 2.0V and 0.8V logic-high and low levels, respectively. When EN is asserted high, the internal digital soft-start cycle slowly ramps up the internal reference and provides a soft-start at the output. This hysteresis provides immunity to the glitches during logic turn-on of the converter.
PAGE 13
2.2MHz, 2A Buck Converters with an Integrated High-Side Switch Power-on Reset (RESET) (MAX5088 Only) RESET is an active-low open-drain output that pulls low when VOUT falls below 92.5% of its nominal set point. RESET goes high impedance when VOUT rises above 92.5% of its nominal set point, the soft-start period is complete, and the 200ms (typ) timeout period has elapsed. Connect a pullup resistor from RESET to a logic voltage or to VL.
PAGE 14
MAX5088/MAX5089 2.2MHz, 2A Buck Converters with an Integrated High-Side Switch Effective Input Voltage Range The MAX5088/MAX5089 can operate with input supplies ranging from 4.5V to 5.5V or 5.5V to 23V. The input voltage range (V+) can be constrained to a minimum by the duty-cycle limitations and to a maximum by the on-time limitation. The minimum input voltage is determined by: V + VDROP1 VIN _ MIN = OUT + VDROP2 − VDROP1 DMAX D MAX is the maximum duty cycle of 87.5% (typ).
PAGE 15
2.2MHz, 2A Buck Converters with an Integrated High-Side Switch ESR = CIN = ∆VESR ∆IP−P   IOUT +   2  IOUT × D(1− D) ∆VQ × fSW where ∆IP−P = (VIN − VOUT ) × VOUT VIN × fSW × L and V D = OUT VIN where IOUT is the output current, D is the duty cycle, and f SW is the switching frequency. Use additional input capacitance at lower input voltages to avoid possible undershoot below the UVLO threshold during transient loading.
PAGE 16
MAX5088/MAX5089 2.2MHz, 2A Buck Converters with an Integrated High-Side Switch rent through the internal power MOSFET (PMOSFET). The total power dissipated in the package must be limited so the junction temperature does not exceed its absolute maximum rating of +150°C at maximum ambient temperature.
PAGE 17
2.2MHz, 2A Buck Converters with an Integrated High-Side Switch GM = VIN ESR V × × FB VOSC ESR+ (2π × fc × L) VOUT First, select the crossover frequency so that: f fC ≤ SW 20 Calculate the LC double-pole frequency, fLC: fLC = where VOSC is the 1VP-P ramp amplitude and VFB = 0.6V.
PAGE 18
MAX5088/MAX5089 2.2MHz, 2A Buck Converters with an Integrated High-Side Switch VOUT R1 COMP gm R2 VREF CCF RF CF Figure 3. Type II Compensation Network VOUT CCF RA R1 CF RF CA gm R2 COMP VREF Figure 4.
PAGE 19
2.2MHz, 2A Buck Converters with an Integrated High-Side Switch PC Board Layout Guidelines Careful PC board layout is critical to achieve lowswitching power losses and clean stable operation. Use a multilayer board whenever possible for better noise immunity. Follow these guidelines for good PC board layout: 1) Solder the exposed pad to a large copper plane under the IC.
PAGE 20
PGND VIN + Figure 5. MAX5088 Buck Configuration ______________________________________________________________________________________ SGND R2 6.04kΩ 1% PGND R3 750Ω 1% R1 27.4kΩ 1% C5 330pF VOUT C1 47µF 35V VIN C8 0.1µF C6 0.1µF VL C9 4.7µF R5 6.04kΩ 1% VIN C3 1200pF R4 10kΩ 1% C7 0.
PAGE 21
PGND VIN + SGND R2 6.04kΩ 1% R3 750Ω 1% R1 27.4kΩ 1% PGND C5 330pF VOUT C1 47µF 35V VIN C8 0.1µF C6 0.1µF VL C9 4.7µF R5 6.04kΩ 1% VIN C3 1200pF R4 10kΩ 1% C7 0.22µF C4 22pF C2 10µF 10 8 11 7 4 3 2 1 SGND VL OSC EN DL SOURCE BST/VDD SYNC PGOOD MAX5089 BYPASS PGND V+ FB COMP DRAIN DRAIN 9 12 15 13 14 16 R6 4.7Ω R7 15Ω JU1 R8 10kΩ VL 3 N1 C10 0.1µF D1 VL R10 10kΩ 4 1 256 R9 10kΩ D2 C11 22µF L1 4.7µH C12 0.
PAGE 22
VIN CIN V+ V+ DRAIN DRAIN OUTPUT1 SOURCE SOURCE OUTPUT2 DUTY CYCLE = 50% SYNC CLKIN SYNC CLKOUT SLAVE MASTER SYNC CLKOUT (MASTER) SOURCE (MASTER) SYNCPHASE SOURCE (SLAVE) CLKOUTPHASE Figure 7. Synchronized Converters Chip Information Pin Configurations (continued) PGND SGND DL PROCESS: BiCMOS SOURCE TOP VIEW 12 11 10 9 SYNC 13 8 VL PGOOD 14 7 V+ 6 BYPASS 5 OSC MAX5089 BST/VDD 15 *EXPOSED PAD. 22 2 3 4 FB 1 COMP EP* + DRAIN EN 16 DRAIN MAX5088/MAX5089 2.
PAGE 23
2.2MHz, 2A Buck Converters with an Integrated High-Side Switch QFN THIN.EPS ______________________________________________________________________________________ 23 MAX5088/MAX5089 Package Information (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.
PAGE 24
MAX5088/MAX5089 2.2MHz, 2A Buck Converters with an Integrated High-Side Switch Package Information (continued) (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.) Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied.