Datasheet

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General Description

The MAX5019/MAX5020 integrate all the building

blocks necessary for implementing DC-DC fixed-fre-

quency power supplies. Either primary- or secondary-

side regulation may be used to implement isolated or

nonisolated power supplies. These devices are current-

mode controllers with an integrated high-voltage start-

up circuit suitable for telecom/industrial voltage range

power supplies. Current-mode control with leading-

edge blanking simplifies control-loop design and inter-

nal ramp compensation circuitry stabilizes the current

loop when operating at duty cycles above 50%

(MAX5019). The MAX5019 allows 85% operating duty

cycle and can be used to implement flyback converters

whereas the MAX5020 limits the operating duty cycle to

less than 50% and can be used in single-ended for-

ward converters. A high-voltage startup circuit allows

these devices to draw power directly from the 18V to

110V input supply during startup. The switching fre-

quency is internally trimmed to 275kHz ±10%, thus

reducing magnetics and filter component costs.

The MAX5019/MAX5020 are available in 8-pin SO

packages.

Warning: The MAX5019/MAX5020 operate with high

voltages. Exercise caution.

Applications

Telecom Power Supplies

Industrial Power Supplies

Networking Power Supplies

Isolated Power Supplies

Features

♦ Wide Input Range: (18V to 110V) or (13V to 36V)

♦ Isolated (without optocoupler) or Nonisolated

Power Supply

♦ Current-Mode Control

♦ Leading-Edge Blanking

♦ Internally Trimmed 275kHz ±10% Oscillator

♦ Low External Component Count

♦ Soft-Start

♦ High-Voltage Startup Circuit

♦ Pulse-by-Pulse Current Limiting

♦ Thermal Shutdown

♦ SO-8 Package

MAX5019/MAX5020

Current-Mode PWM Controllers with Integrated

Startup Circuit

________________________________________________________________ Maxim Integrated Products 1

GND

NDRVV

V+

8-SO

TOP VIEW

MAX5019/

MAX5020

SS_SHDN

Pin Configuration

Ordering Information

NDRV

OUT

MAX5020

V+

SS_SHDN

GND

Typical Operating Circuit

19-2115; Rev 0; 7/01

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.

PART TEMP. RANGE PIN-PACKAGE

MAX5019CSA* 0°C to +70°C8-SO

MAX5019ESA* -40°C to +85°C8-SO

MAX5020CSA* 0°C to +70°C8-SO

MAX5020ESA* -40°C to +85°C8-SO

*See Selector Guide at end of data sheet.

Summary of content (14 pages)

PAGE 1
9-2115; Rev 0; 7/01 Current-Mode PWM Controllers with Integrated Startup Circuit The MAX5019/MAX5020 integrate all the building blocks necessary for implementing DC-DC fixed-frequency power supplies. Either primary- or secondaryside regulation may be used to implement isolated or nonisolated power supplies. These devices are currentmode controllers with an integrated high-voltage startup circuit suitable for telecom/industrial voltage range power supplies.
PAGE 2
MAX5019/MAX5020 Current-Mode PWM Controllers with Integrated Startup Circuit ABSOLUTE MAXIMUM RATINGS V+ to GND ……………………………………...……-0.3V to +120V VDD to GND.………………………………….……….-0.3V to +40V VCC to GND.………………….……………………-0.3V to +12.5V FB, NDRV, SS_SHDN, CS to GND .……-0.3V to VCC + 0.3V VDD and VCC Current …………………...…………………..20mA NDRV Current Continuous...………………………………….25mA NDRV Current for Less than 1µs..………….…………….……±1A Continuous Power Dissipation (TA = +70°C) 8-Pin SO (derate 5.88mW/°C above +70°C) .………..
PAGE 3
Current-Mode PWM Controllers with Integrated Startup Circuit (VDD = 13V, a 10µF capacitor connects VCC to GND, VCS = 0, V+ = 48V, 0.1µF capacitor connected from SS_SHDN to GND, NDRV = open circuit, VFB = 3V, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.
PAGE 4
Typical Operating Characteristics (continued) (V+ = 48V, VDD = 13V, CS = GND, NRDV is open circuit, TA = +25°C, unless otherwise noted.) 47.2 47.0 1.59 1.58 1.57 1.56 0 20 60 V+ INPUT CURRENT vs. TEMPERATURE (AFTER STARTUP) V+ SHUTDOWN CURRENT vs. TEMPERATURE 40 60 80 MAX5019 toc07 13.80 13.75 V+ = 110V, VDD = 13V, FB = GND 13.70 13.65 13.60 0 20 40 60 182.0 V+ = 110V, FB = SS_SHDN = GND 181.5 181.0 180.5 180.0 -20 0 20 40 60 TEMPERATURE (°C) TEMPERATURE (°C) NDRV RESISTANCE vs.
PAGE 5
Current-Mode PWM Controllers with Integrated Startup Circuit MAX5020 MAXIMUM DUTY CYCLE vs. VDD 269.5 269.0 268.5 FB = GND 268.0 47.8 VFB = 4V, CS = GND 47.7 47.6 47.5 DEVICE POWERED FROM VDD 47.4 47.3 20 25 30 35 9.5 0 40 5 10 15 20 25 30 35 0 5 10 15 VDD (V) VDD (V) 25 30 35 40 V+ SUPPLY CURRENT vs. V+ VOLTAGE (AFTER STARTUP) 1.59 1.58 VFB = VDD = GND 1.56 1.55 1.54 1.53 16 14 V+ LEAKAGE CURRENT (µA) MAX5019 toc16 1.60 1.57 20 VDD (V) V+ SUPPLY CURRENT vs.
PAGE 6
Current-Mode PWM Controllers with Integrated Startup Circuit MAX5019/MAX5020 Pin Description PIN NAME FUNCTION V+ High-Voltage Startup Input. Connect directly to an input voltage between 18V to 110V. Connects internally to a high-voltage linear regulator that generates VCC during startup. 2 VDD VDD is the Input of the Linear Regulator that Generates VCC. For supply voltages less than 36V, VDD and V+ can both be connected to the supply.
PAGE 7
Current-Mode PWM Controllers with Integrated Startup Circuit MAX5019/MAX5020 VDD VDD-OK V+ IN IN HIGHVOLTAGE REGULATOR GND EN BIAS WINDING REGULATOR OUT EN OUT 0.7V VCC MAX5019 ONLY UVLO SLOPE COMPENSATION 26mV/µs 6.6V 275kHz OSCILLATOR VCC R NDRV Q 26mV/µs 80%/50% DUTY CYCLE CLAMP 1MΩ FB S ∑ 50kΩ ILIM PWM 125mV CS ERROR AMP 5kΩ VCC SS_SHDN 70ns BLANKING 4µA 3R 2.4V BUF R 0.25V Figure 1.
PAGE 8
MAX5019/MAX5020 Current-Mode PWM Controllers with Integrated Startup Circuit 1N4148 6 VIN (36V TO 72V) NT N 14 R CMHD2003 V+ VDD CDD 4.7µF VCC CCC 10µF MAX5020 NDRV CIN 3✕ 0.47µF NP 14 SBL204OCT NS 5 L1 4.7µH VOUT 5V/10A COUT 3✕ 560µF 20Ω 0.1µF 1nF M1 IRF640N R1 2kΩ CS 100Ω SS_SHDN CSS 0.1µF RSENSE 100mΩ GND FB R2 2kΩ CFB (OPTIONAL) Figure 2.
PAGE 9
Current-Mode PWM Controllers with Integrated Startup Circuit V+ VDD VOUT CCC COUT CIN NP CDD VCC MAX5019 MAX5020 MAX5019/MAX5020 NT VIN NS M1 NDRV CS 100Ω SS_SHDN RSENSE R1 CSS GND FB R2 Figure 3. Nonisolated Flyback Converter NT VOUT VIN V+ VDD COUT CIN NP CDD NS R1 FB R2 MAX5019 MAX5020 VCC NDRV M1 CS CCC 100Ω RSENSE SS_SHDN GND CSS Figure 4. Isolated Flyback Converter to 2.4V, the internal voltage reference. Pull VSS_SHDN below 0.25V to disable the controller.
PAGE 10
MAX5019/MAX5020 Current-Mode PWM Controllers with Integrated Startup Circuit pass filter (Figures 2, 3). Select the current-sense resistor, RSENSE according to the following equation: RSENSE = 0.465V / ILimPrimary where ILimPrimary is the maximum peak primary-side current. When VCS > 465mV, the power MOSFET switches off. The propagation delay from the time the switch current reaches the trip level to the driver turn-off time is 180ns.
PAGE 11
Current-Mode PWM Controllers with Integrated Startup Circuit  R  VOUT ≅ VREF 1+ 1   R2  R1 // R2 << 50kΩ VREF = VSS_SHDN ≅ 2.4V where VREF is the reference voltage of the shunt regulator, and R1 and R2 are the resistors shown in Figures 2 and 3. 3) The turns ratio of the transformer is calculated based on the minimum input voltage and the lower limit of the maximum duty cycle for the MAX5020 (44%).
PAGE 12
MAX5019/MAX5020 Current-Mode PWM Controllers with Integrated Startup Circuit 14   VDSMAX ≥ 72V × 1 +  = 144V  14  Choose MOSFETs with appropriate avalanche power ratings. 5) Choose the tertiary winding turns ratio (NT/NP) so that the minimum input voltage provides the minimum operating voltage at VDD (13V). Use the following equation to calculate the tertiary winding turns ratio: VDDMIN + 0.7 × NP ≤ NT ≤ VIN_MIN VDDMAX + 0.7 × NP VIN_MAX where: VDDMIN is the minimum VDD supply voltage (13V).
PAGE 13
Current-Mode PWM Controllers with Integrated Startup Circuit Power FETS Current-Sense Resistors Diodes Capacitors Magnetics International Rectifier www.irf.com Fairchild www.fairchildsemi.com Vishay-Siliconix www.vishay.com/brands/siliconix/main.html Dale-Vishay www.vishay.com/brands/dale/main.html IRC www.irctt.com/pages/index.cfm On Semi www.onsemi.com General Semiconductor www.gensemi.com Central Semiconductor www.centralsemi.com Sanyo www.sanyo.com Taiyo Yuden www.t-yuden.
PAGE 14
Current-Mode PWM Controllers with Integrated Startup Circuit SOICN.EPS MAX5019/MAX5020 Package Information 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.