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General Description

The MAX5051 is a clamped, two-switch power-supply

controller IC. This device can be used both in forward or

flyback configurations with input voltage ranges from 11V

to 76V. It provides comprehensive protection mech-

anisms against possible faults, resulting in very high relia-

bility power supplies. When used in conjunction with sec-

ondary-side synchronous rectification, power-supply

efficiencies can easily reach 92% for a +3.3V output

power supply operated from a 48V bus. The integrated

high- and low-side gate drivers provide more than 2A of

peak gate-drive current to two external N-channel

MOSFETs. Low startup current reduces the power loss

across the bootstrap resistor. A feed-forward voltage-

mode topology provides excellent line rejection while

avoiding the pitfalls of traditional current-mode control.

The MAX5051 power-supply controller is primary as

well as secondary-side parallelable, allowing the

design of scaleable power systems when necessary.

When paralleling the primary side, dedicated pins allow

for simultaneous wakeup or shutdown of all paralleled

units, thus preventing current-hogging during startup or

fault conditions.

The MAX5051 generates a lookahead signal for driving

secondary-side synchronous MOSFETs. Special

primary-side synchronization inputs/outputs allow two

primaries to be operated 180° out of phase for increased

output power and lower input ripple currents.

The MAX5051 is available in a 28-pin TSSOP-EP

package and operates over a wide -40°C to +125°C

temperature range.

Warning: The MAX5051 is designed to work with

high voltages. Exercise caution.

Applications

High-Efficiency, Isolated Telecom/Datacom

Power Supplies

48V and 12V Server Power Supplies

48V Power-Supply Modules

42V Automotive Power Systems

Industrial Power Supplies

Features

♦ Wide Input Voltage Range, 11V to 76V

♦ Voltage Mode with Input Voltage Feed-Forward

♦ Ripple-Phased Parallel Topology for High

Current/Power Output

♦ 2A Integrated High- and Low-Side MOSFET

Drivers

♦ SYNCIN And SYNCOUT Pins Enable 180° Out-Of-

Phase Operation

♦ Programmable Brownout and Bootstrap UVLOs

♦ High-Side Driver Bootstrap Capacitor Precharge

Driver

♦ Low Current-Limit Threshold for High Efficiency

♦ Programmable Switching Frequency

♦ Reference Voltage Soft-Start for Startup Without

Overshoots

♦ Startup Synchronization with Multiple Paralleled

Primaries

♦ Programmable Integrating Current-Limit Fault

Protection

♦ Look-Ahead PWM Signal for Secondary-Side

Synchronous Rectifier Drivers

♦ Look-Ahead Drivers for Either A High-Speed

Optocoupler or Pulse Transformer

♦ Wide -40°C to +125°C Operating Range

♦ Thermally Enhanced 28-Pin TSSOP Package

MAX5051

Parallelable, Clamped Two-Switch

Power-Supply Controller IC

________________________________________________________________ Maxim Integrated Products 1

Ordering Information

19-2964; Rev 0; 8/03

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.

EVALUATION KIT

AVAILABLE

PART TEMP RANGE PIN-PACKAGE

MAX5051AUI -40°C to +125°C 28-TSSOP-EP*

*EP = Exposed pad.

Pin Configuration appears at end of data sheet.

Summary of content (21 pages)

PAGE 1
9-2964; Rev 0; 8/03 KIT ATION EVALU E L B AVAILA Parallelable, Clamped Two-Switch Power-Supply Controller IC The MAX5051 power-supply controller is primary as well as secondary-side parallelable, allowing the design of scaleable power systems when necessary. When paralleling the primary side, dedicated pins allow for simultaneous wakeup or shutdown of all paralleled units, thus preventing current-hogging during startup or fault conditions.
PAGE 2
MAX5051 Parallelable, Clamped Two-Switch Power-Supply Controller IC ABSOLUTE MAXIMUM RATINGS AVIN, PVIN, XFRMRH to GND................................-0.3V to +80V BST to GND ............................................................-0.3V to +95V BST, DRVH to XFRMRH..........................................-0.3V to +12V REG9, DRVDD, DRVL to GND................................-0.3V to +12V DRVB, LXVDD, LXL, LXH to GND ..........................-0.3V to +12V UVLO, STT, COMP, CON to GND ....................
PAGE 3
Parallelable, Clamped Two-Switch Power-Supply Controller IC (AVIN = 12V, PVIN = 12V, VUVLO = VSTT = 3V, VCON = 3V, RRCOSC = 24kΩ, CCSS = 10nF, CRCOSC = 100pF, CREG9 = 4.7µF, CREG5 = 4.7µF, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C. All driver, voltage-regulator, and reference outputs unconnected except for bypass capacitors.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 1.215 1.235 1.
PAGE 4
MAX5051 Parallelable, Clamped Two-Switch Power-Supply Controller IC ELECTRICAL CHARACTERISTICS (continued) (AVIN = 12V, PVIN = 12V, VUVLO = VSTT = 3V, VCON = 3V, RRCOSC = 24kΩ, CCSS = 10nF, CRCOSC = 100pF, CREG9 = 4.7µF, CREG5 = 4.7µF, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C. All driver, voltage-regulator, and reference outputs unconnected except for bypass capacitors.) PARAMETER SYMBOL SYNCOUT Voltage High CONDITIONS Sourcing 1.2mA SYNCOUT Voltage Low MIN TYP 4.
PAGE 5
Parallelable, Clamped Two-Switch Power-Supply Controller IC (AVIN = 12V, PVIN = 12V, VUVLO = VSTT = 3V, VCON = 3V, RRCOSC = 24kΩ, CCSS = 10nF, CRCOSC = 100pF, CREG9 = 4.7µF, CREG5 = 4.7µF, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C. All driver, voltage-regulator, and reference outputs unconnected except for bypass capacitors.
PAGE 6
Typical Operating Characteristics (VAVIN = VPVIN = 12V, VUVLO = VSTT = 3V, VCON = 3V, RRCOSC = 24kΩ, CCSS = 10nF, CRCOSC = 100pF, CREG9 = 4.7µF, CREG5 = 4.7µF, TA = +25°C, unless otherwise noted.) AVIN STANDBY CURRENT vs. TEMPERATURE 260 250 240 230 220 20 30 40 50 60 70 230 220 210 200 MAX5051 toc03 500 400 300 200 100 0 -50 80 -25 0 25 50 75 100 125 10 40 50 60 PVIN SUPPLY VOLTAGE (V) PVIN STANDBY CURRENT vs. TEMPERATURE PVIN STARTUP VOLTAGE vs.
PAGE 7
Parallelable, Clamped Two-Switch Power-Supply Controller IC AVIN SUPPLY CURRENT vs. TEMPERATURE 4.996 4.995 4.994 4.993 4.992 500 400 300 200 4.990 -25 0 25 50 75 100 -50 -25 0 25 50 75 100 TEMPERATURE (°C) TEMPERATURE (°C) SOFT-START/REFERENCE VOLTAGE vs. TEMPERATURE CSS SOFT-START CURRENT vs. TEMPERATURE 1.230 1.225 1.220 1.215 1.210 6.8 -25 0 25 50 75 100 125 TEMPERATURE (°C) UVLO THRESHOLD vs. TEMPERATURE 1.240 85 1.235 1.230 80 UVLO (V) 1.235 6.
PAGE 8
Typical Operating Characteristics (continued) (VAVIN = VPVIN = 12V, VUVLO = VSTT = 3V, VCON = 3V, RRCOSC = 24kΩ, CCSS = 10nF, CRCOSC = 100pF, CREG9 = 4.7µF, CREG5 = 4.7µF, TA = +25°C, unless otherwise noted.) GAIN 210 180 60 155 150 150 40 120 90 20 PHASE 145 60 0 -20 0.01 140 -25 0 25 50 75 100 125 0.1 1 10 100 FREQUENCY (kHz) DRVH AND DRVL RDSON vs. TEMPERATURE LXL AND LXH RDSON vs. TEMPERATURE RDSON (Ω) 2.0 LXH SOURCING 10mA 8 7 1.
PAGE 9
Parallelable, Clamped Two-Switch Power-Supply Controller IC CS CURRENT LIMIT TO DRVH PROPAGATION DELAY vs. TEMPERATURE CON TO DRVL PROPAGATION DELAY vs.
PAGE 10
Parallelable, Clamped Two-Switch Power-Supply Controller IC MAX5051 Pin Description (continued) PIN NAME FUNCTION 13 LXH Synchronous-Pulse Transformer Driver, PMOS Open Drain. LXH is the high-side driver for the secondaryside synchronous-pulse transformer. LXH can also drive a high-speed switching optocoupler. If not used, connect LXH to LXVDD. 14 LXL Synchronous-Pulse Transformer Driver, NMOS Open Drain. LXL is the low-side driver for the secondaryside synchronous-pulse transformer.
PAGE 11
Parallelable, Clamped Two-Switch Power-Supply Controller IC 9V LDO PVIN REG9 5V LDO REG9 OK 18R REG5 REG5 OK MAX5051 OVER TEMP STT R THERMAL SHUTDOWN BST LEVEL SHIFT 1.25V 1.125V 25µs RISINGEDGE DELAY DRVH 60ns RISINGEDGE DELAY SHDN XFRMRH DRVDD DRVL UVLO PGND 1.25V 1.125V LXVDD INTERNAL REGULATOR AVIN INTERNAL SUPPLY 1.25V REFERENCE LEVEL SHIFT LXH LXL 80µA OSC RCOSC FLTINT SYNCIN 2.7V/1.8V SYNCOUT CS RCFF 2.
PAGE 12
MAX5051 Parallelable, Clamped Two-Switch Power-Supply Controller IC Detailed Description The MAX5051 controller IC is designed for two-switch forward converter power-supply topologies. It incorporates an advanced set of protection features that makes it uniquely suitable when high reliability and comprehensive fault protection are required, as in power supplies intended for telecommunication equipment. The device operates over a wide 11V to 76V supply range.
PAGE 13
Parallelable, Clamped Two-Switch Power-Supply Controller IC D4 MA111CT R6 47Ω C8 4.7µF D3 BAT46W R5 10Ω C11 0.1µF R12 1MΩ C5 1µF BST REG9 PVIN FLTINT SYNCIN AVIN CSS STT C7 4.7µF C12 220nF XFRMRH GND N1 SI4486 DRVDD D1 RCOSC C13 100pF DRVH STARTUP MAX5051 USED FOR BOOST CAPACITOR PRECHARGE DRVL CS PGND fs = 250kHz L1 2µH D5 T1 3.
PAGE 14
MAX5051 Parallelable, Clamped Two-Switch Power-Supply Controller IC diode is a high-voltage, small-signal Schottky type. It may be helpful to connect a resistor in series with this diode to minimize noise as well as reduce the peak charging currents. As in any other switching powersupply circuit, the gate-drive loops must be kept to a minimum. Plan PC board layout with the critical current carrying loops of the circuit as a starting point.
PAGE 15
Parallelable, Clamped Two-Switch Power-Supply Controller IC CCSS = 56µF / s × t SS where CCSS is the capacitor connected to CSS, tSS is the soft-start time required for the output voltage to rise from 0V to the rated output voltage. This only applies when this amplifier is used for output voltage regulation. PWM Ramp The PWM ramp is generated at RCFF. Connect a capacitor CRCFF from RCFF to ground and a resistor R RCFF from RCFF to AVIN. The ramp generated on RCFF is internally offset by 2.
PAGE 16
MAX5051 Parallelable, Clamped Two-Switch Power-Supply Controller IC Normally PVIN is derived from a tertiary winding of the transformer. However, at startup there is no energy delivered through the transformer, hence, a special bootstrap sequence is required. Figure 6 shows the voltages on PVIN, REG9, and REG5 during startup. Initially, PVIN, REG9, and REG5 are 0V. After the input voltage is applied, C21 (Figure 8) charges PVIN through the startup resistor, R22, to an intermediate voltage.
PAGE 17
Parallelable, Clamped Two-Switch Power-Supply Controller IC I t CFLTINT = FLTINT SH 0.9V where IFLTINT = 90µA, tSH is the desired fault integration time after the first shutdown cycle during which current-limit events from the current-limit comparator are ignored. For example, a 0.1µF capacitor gives a fault integration time of 2.25ms. Some testing may be required to fine-tune the actual value of the capacitor. To calculate the required bleed resistance RFLTINT, use the following formula: RFLTINT = tRT 0.
PAGE 18
2 R27 10Ω PVIN REG9 REG5 TP3 3 4 C19 1µF C18 100pF C17 0.33µF R11 360Ω R3 2.2kΩ REG5 LXH REG5 C6 0.1µF C3 4.7µF C4 4.7µF R15 31.6kΩ 1% D8 R16 10.5kΩ 1% C2 390pF C5 4700pF TP1 C1 100pF 1 R25 100kΩ R21 24.9kΩ 1% C24 1000pF +VIN REG5 RCFF 14 13 12 11 10 9 8 7 6 17 18 19 20 21 2 1 REG9 R12 100kΩ 1% R19 475Ω Figure 8. Schematic of a 48V Input 3.
PAGE 19
Parallelable, Clamped Two-Switch Power-Supply Controller IC 90 7 POWER DISSIPATION (W) 8 EFFICIENCY (%) 85 80 75 70 65 MAX5051 95 6 5 4 3 2 1 60 0 0 2 4 6 8 10 12 14 0 LOAD CURRENT (A) 2 4 6 8 10 12 14 LOAD CURRENT (A) Figure 9. Efficiency at Nominal Output Voltage vs. Load Current 48V Nominal Input Voltage Figure 10. Power Dissipation at Nominal Output Voltage vs. Load Current for 48V Input Voltage. RL = 0.
PAGE 20
MAX5051 Parallelable, Clamped Two-Switch Power-Supply Controller IC A IOUT 10A/div B IOUT 10A/div VOUT 50mV/div A: 1ms/div B: 20ms/div 2µs/div Figure 13. Output Voltage Ripple At Nominal Input Voltage and Full Load Current (Scope Bandwidth = 20MHz) Pin Configuration Figure 14.
PAGE 21
Parallelable, Clamped Two-Switch Power-Supply Controller IC TSSOP 4.4mm BODY.EPS 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.