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General Description

The MAX17499/MAX17500 current-mode PWM con-

trollers contain all the control circuitry required for the

design of wide-input-voltage isolated and nonisolated

power supplies. The MAX17499 is well suited for low

input voltage (9.5V DC to 24V DC) power supplies. The

MAX17500 is well suited for universal input (rectified

85V AC to 265V AC) or telecom (-36V DC to -72V DC)

power supplies.

The ICs contain an internal error amplifier that regulates

the tertiary winding output voltage that is used in prima-

ry-side-regulated isolated power supplies. Primary-side

regulation eliminates the need for an optocoupler. An

input undervoltage lockout (UVLO) is provided for pro-

gramming the input-supply start voltage and to ensure

proper operation during brownout conditions. An open-

drain UVLO flag output, with 210μs internal delay,

allows the sequencing of a secondary-side controller.

The input-supply start voltage is externally programma-

ble with a voltage-divider. A UVLO/EN input is used to

shut down the devices. Internal digital soft-start elimi-

nates output voltage overshoot.

The MAX17500 has an internal bootstrap UVLO with

large hysteresis that requires a minimum 23.6V for start-

up. The MAX17499 does not have the internal bootstrap

UVLO and can be biased directly from a minimum volt-

age of 9.5V.

The switching frequency for the ICs is programmable

with an external resistor. The MAX17499A/MAX17500A

provide a 50% maximum duty-cycle limit, while the

MAX17499B/MAX17500B provide a 75% maximum

duty-cycle limit. These devices are available in 10-pin

μMAX

packages and are rated for operation over the

-40°C to +125°C temperature range.

Features

o Current-Mode Control

o Programmable Switching Frequency Up to 625kHz

o Accurate UVLO Threshold (1%)

o Open-Drain UVLO Flag Output with Internal Delay

o 36V to 72V Telecom Voltage Range

o Universal Offline Input Voltage Range

Rectified 85V AC to 265V AC (MAX17500)

o 9.5V to 24V Input (MAX17499)

o Digital Soft-Start

o Internal Bootstrap UVLO with Large Hysteresis

(MAX17500)

o Internal Error Amplifier with 1.5% Accurate

Reference

o 50µA (typ) Startup Supply Current

o 50% Maximum Duty-Cycle Limit

(MAX17499A/MAX17500A)

o 75% Maximum Duty-Cycle Limit

(MAX17499B/MAX17500B)

o 60ns Cycle-by-Cycle Current-Limit Propagation

Delay

o Available in Tiny 10-Pin µMAX Packages

Applications

1/2, 1/4, and 1/8 Brick Power Modules

High-Efficiency, Isolated Telecom Power

Supplies

Networking/Servers

Isolated Keep-Alive Power Supplies

12V Boost and SEPIC Regulators

Isolated and Nonisolated High-Brightness LED

Power Supplies

Industrial Power Conversion

MAX17499/MAX17500

Current-Mode PWM Controllers with

Programmable Switching Frequency

________________________________________________________________

Maxim Integrated Products

Ordering Information

19-5485; Rev 1; 7/11

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.

Warning: The ICs are designed to work with high voltages. Exercise caution.

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

EVALUATION KIT

AVAILABLE

Selector Guide appears at end of data sheet.

PART D

MAX

(%) STARTUP VOLTAGE (V) TEMP RANGE PIN-PACKAGE

MAX17499AAUB+ 50 9.5 -40°C to +125°C 10 μMAX

MAX17499BAUB+ 75 9.5 -40°C to +125°C 10 μMAX

MAX17500AAUB+ 50 22 -40°C to +125°C 10 μMAX

MAX17500BAUB+ 75 22 -40°C to +125°C 10 μMAX

μMAX is a registered trademark of Maxim Integrated Products, Inc.

Summary of content (18 pages)

PAGE 1
9-5485; Rev 1; 7/11 KIT ATION EVALU E L B AVAILA Current-Mode PWM Controllers with Programmable Switching Frequency Features The MAX17499/MAX17500 current-mode PWM controllers contain all the control circuitry required for the design of wide-input-voltage isolated and nonisolated power supplies. The MAX17499 is well suited for low input voltage (9.5V DC to 24V DC) power supplies. The MAX17500 is well suited for universal input (rectified 85V AC to 265V AC) or telecom (-36V DC to -72V DC) power supplies.
PAGE 2
MAX17499/MAX17500 Current-Mode PWM Controllers with Programmable Switching Frequency ABSOLUTE MAXIMUM RATINGS IN to GND ...............................................................-0.3V to +30V IN Clamp (internal shunt) Current .........................................5mA VCC to GND ............................................................-0.3V to +13V FB, COMP, UVLO/EN, RT, CS to GND .....................-0.3V to +6V UFLG to GND .........................................................-0.
PAGE 3
Current-Mode PWM Controllers with Programmable Switching Frequency (VIN = +12V (for MAX17500, bring VIN up to 23.6V for startup), 10nF bypass capacitors at IN and VCC, R12 = 15kΩ (MAX17499A/ MAX17500A), R12 = 7.5kΩ (MAX17499B/MAX17500B), R15 = 1kΩ, C6 = 100nF (see the Typical Application Circuit), NDRV = open, VUVLO/EN = +1.4V, VFB = +1.0V, COMP = open, VCS = 0V, TA = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.
PAGE 4
ELECTRICAL CHARACTERISTICS (continued) (VIN = +12V (for MAX17500, bring VIN up to 23.6V for startup), 10nF bypass capacitors at IN and VCC, R12 = 15kΩ (MAX17499A/ MAX17500A), R12 = 7.5kΩ (MAX17499B/MAX17500B), R15 = 1kΩ, C6 = 100nF (see the Typical Application Circuit), NDRV = open, VUVLO/EN = +1.4V, VFB = +1.0V, COMP = open, VCS = 0V, TA = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.
PAGE 5
Current-Mode PWM Controllers with Programmable Switching Frequency VIN = 19V MAX17500 WHEN IN BOOTSTRAP UVLO 60 MAX17499/500 toc06 1.175 2.0 MAX17499/500 toc05 UVLO/EN FALLING VIN = 24V fSW = 350kHz 1.9 1.165 IIN (mA) 1.170 ISTART (µA) VUVLO/EN (V) 65 MAX17499/500 toc04 1.180 VIN SUPPLY CURRENT AFTER STARTUP vs. TEMPERATURE VIN SUPPLY CURRENT IN UVLO vs. TEMPERATURE UVLO/EN SHUTDOWN THRESHOLD vs. TEMPERATURE 55 1.8 1.7 1.160 50 1.6 1.
PAGE 6
Current-Mode PWM Controllers with Programmable Switching Frequency Typical Operating Characteristics (continued) (VUVLO/EN = +1.4V, VFB = +1V, COMP = open, VCS = 0V, TA = +25°C, unless otherwise noted.) PROPAGATION DELAY FROM CURRENT-LIMIT COMPARATOR INPUT TO NDRV vs. TEMPERATURE 50 UVLO/EN RISING 4 3 2 45 206μs 1 40 10 1 10 100 UVLO/EN FALLING 0 -15 -40 1000 10 35 60 85 -15 -40 10 35 60 TIMING RESISTOR (kΩ) TEMPERATURE (°C) TEMPERATURE (°C) UVLO/EN-TO-UFLG PROPAGATION DELAY vs.
PAGE 7
Current-Mode PWM Controllers with Programmable Switching Frequency ERROR AMPLIFIER OPEN-LOOP GAIN AND PHASE vs. FREQUENCY NDRV HIGH-OUTPUT IMPEDANCE vs. TEMPERATURE 40 GAIN 40 4.2 3.8 120 80 60 GAIN (dB) RON (Ω) 4.6 80 0 -40 20 0 -80 PHASE -20 PHASE (DEGREES) SOURCING 20mA MAX17499/500 toc22 100 MAX17499/500 toc21 5.0 -120 3.4 -40 -160 -60 3.0 -15 -40 10 35 60 0.
PAGE 8
MAX17499/MAX17500 Current-Mode PWM Controllers with Programmable Switching Frequency Pin Description (continued) PIN NAME 7 GND Ground Connection FUNCTION 8 NDRV External n-Channel MOSFET Gate Connection 9 VCC 10 IN Gate-Drive Supply. Internally generated supply from IN. Decouple VCC with a 10nF or larger capacitor to GND. IN Supply. Decouple with a 10nF or larger capacitor to GND. For bootstrapped operation (MAX17500), connect a startup resistor from the input supply line to IN.
PAGE 9
Current-Mode PWM Controllers with Programmable Switching Frequency Current-Mode Control Loop The advantages of current-mode control over voltagemode control are twofold. First, there is the feed-forward characteristic brought on by the controller’s ability to adjust for variations in the input voltage on a cycle-by-cycle basis. Secondly, the stability requirements of the current-mode controller are reduced to that of a single-pole system unlike the double pole in voltage-mode control.
PAGE 10
MAX17499/MAX17500 Current-Mode PWM Controllers with Programmable Switching Frequency point, the internal regulator begins charging C2 (see Figure 1). Only 50μA of the current supplied through R1 is used by the MAX17500; the remaining input current charges C1 and C2. The charging of C2 stops when the VCC voltage reaches approximately 9.5V, while the voltage across C1 continues rising until it reaches the wake-up level of 21.6V.
PAGE 11
Current-Mode PWM Controllers with Programmable Switching Frequency tSS = 1984 fNDRV where fNDRV is the switching frequency at the NDRV output. Figure 4 shows the soft-start regulated output of a power supply using the MAX17500 during startup. n-Channel MOSFET Switch Driver The NDRV output drives an external n-channel MOSFET. The internal regulator output (VCC), set to approximately 9V, drives NDRV.
PAGE 12
MAX17499/MAX17500 Current-Mode PWM Controllers with Programmable Switching Frequency circuit in Figure 6, calculate the output voltage using the following equation: VOUT = NS NT ⎡⎛ ⎤ R1 ⎞ VREF + VD6 ⎥ − VD2 ⎢⎜ 1 + ⎟ ⎣⎝ R2 ⎠ ⎦ where NS is the number of secondary winding turns, NT is the number of tertiary winding turns, and both VD6 and VD2 are the diode drops at the respective outputs. the maximum startup bias of the device (90μA) and the charging current for C1 and C2.
PAGE 13
Current-Mode PWM Controllers with Programmable Switching Frequency Another method for bootstrapping the power supply is to use a bias winding that is in-phase with the MOSFET on-time (see Figure 5). In this case, the amount of capacitance required at IN (C1) is much smaller. However, the input voltage cannot have a range greater than approximately 2:1 (primary-winding voltage to bias-winding voltage ratio).
PAGE 14
MAX17499/MAX17500 Current-Mode PWM Controllers with Programmable Switching Frequency FB_P IN D8 C16 1μF 35V R6 33kΩ 36V TO 72V +VIN +VIN D6 C12 15μF 35V R7 1.2kΩ D7 OPEN R12 1.2kΩ 4 R8 OPEN 28T 35μH C10 OPEN C3 68μF 6.3V 5T 2 6 1 FB_P L1 D1 7 SGND C13 1μF D4 VOUT1 5V/1.5A C4 22μF SGND 6.3V C6 0.0047μF 250V AC D3 OPEN R1 22.6kΩ 1% C15 1μF D5 8 C2 1μF 100V C1 1μF 100V 15V/100mA C5 47μF 25V 10 12T 15T VOUT2 D2 5 T1 9 3 -VIN IN 3 R2 +VIN 2.49kΩ 1% R9 75kΩ 1% R3 1.
PAGE 15
Current-Mode PWM Controllers with Programmable Switching Frequency D1 MAX17499/MAX17500 L1 12V 15V R2 UFLG R5 IN Q1 NDRV VCC MAX17499 CS C4 C3 C1 C2 GND COMP R1 FB UVLO/EN RT R6 C6 R3 R12 R15 0V Figure 8. 12V to 15V Output Boost Regulator Figure 8 shows the 12V to 15V output boost regulator. Layout Recommendations Typically, there are two sources of noise emission in a switching power supply: high di/dt loops and high dV/dt surfaces.
PAGE 16
MAX17499/MAX17500 Current-Mode PWM Controllers with Programmable Switching Frequency Typical Application Circuit D2 T1 D1 R5 R2 C4 R1 UVLO/EN UFLG FB C2 + COMP 36V TO 72V C5 - R11 R3 CS 1 2 10 MAX17500 9 3 8 4 7 5 6 IN VCC NDRV Q1 GND RT R6 C6 C2 R15 16 R12 C1 R4 ______________________________________________________________________________________ VOUT
PAGE 17
Current-Mode PWM Controllers with Programmable Switching Frequency IN IN IN CLAMP 26.1V VCC VCC REGULATOR DIGITAL SOFT-START BOOTSTRAP UVLO REFERENCE 1.23V REG_OK * VL (INTERNAL 5.25V SUPPLY) 21.6V 9.74V 210μs DELAY UFLG UVLO UVLO/EN N 1.23V 1.17V COMP DRIVER S FB NDRV Q ERROR AMP R CPWM OSCILLATOR 1.4V CS GND VCS 1V MAX17499 MAX17500 ILIM RT *MAX17500 ONLY Chip Information Selector Guide PART* BOOTSTRAP STARTUP UVLO VOLTAGE (V) MAX DUTY CYCLE (%) MAX17499A No 9.
PAGE 18
Current-Mode PWM Controllers with Programmable Switching Frequency MAX17499/MAX17500 Revision History REVISION NUMBER REVISION DATE 0 9/10 Initial release 1 7/11 Changed operating temperature from -40°C to +85°C to -40°C to +125°C DESCRIPTION PAGES CHANGED — 1–4 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied.