Rainbow Electronics MAX5068 User Manual

General Description

The MAX5068 is a high-frequency, current-mode,
pulse-width modulation (PWM) controller that integrates
all the building blocks necessary for implementing AC­DC or DC-DC fixed-frequency power supplies. Isolated
or nonisolated power supplies are easily constructed
using either primary- or secondary-side regulation.
Current-mode control with leading-edge blanking sim­plifies control-loop design, and a programmable inter­nal slope-compensation circuit stabilizes the current
loop when operating at duty cycles above 50%. The
MAX5068A/B limit the maximum duty cycle to 50% for
use in single-ended forward converters. The
MAX5068C/D/E/F allow duty cycles up to 75%. The
MAX5068 features an accurate externally programma­ble oscillator that simplifies system design.

An input undervoltage lockout (UVLO) programs the
input-supply startup voltage and ensures proper opera­tion during brownout conditions.

A single external resistor programs the output switching
frequency from 12.5kHz to 1.25MHz. The MAX5068A/
B/C/E provide a SYNC input for synchronization to an
external clock. The maximum FET-driver duty cycle is
50% for the MAX5068A/B and 75% for the MAX5068C/
D/E/F. Programmable hiccup current limit provides
additional protection under severe faults.

The MAX5068 is specified over the -40°C to +125°C
automotive temperature range and is available in a
16-pin thermally enhanced TSSOP-EP package. Refer to
the MAX5069 data sheet for dual FET-driver applications.

Warning: The MAX5068 is designed to work with high
voltages. Exercise caution.

Applications

Universal-Input AC Power Supplies
Isolated Telecom Power Supplies
Networking System Power Supplies
Server Power Supplies
Industrial Power Conversion

Features

♦ Current-Mode Control with 47µA (typ) Startup

Current

♦ Resistor-Programmable ±4.5% Accurate

Switching Frequency:

25kHz to 1.25MHz (MAX5068A/B)

12.5kHz to 625kHz (MAX5068C/D/E/F)

♦ Rectified 85VACto 265VACor 36VDCto 72V

DC

Input (MAX5068A/C/D)

♦ Input Directly Driven from 10.8V to 24V

(MAX5068B/E/F)

♦ Frequency Synchronization Input

(MAX5068A/B/C/E)

♦ Programmable Dead Time and Slope

Compensation

♦ Programmable Startup Voltage (UVLO)
♦ Programmable UVLO Hysteresis

(MAX5068A/B/D/F)

♦ Integrating Fault Protection (Hiccup)
♦ -40°C to +125°C Automotive Temperature Range
♦ 16-Pin Thermally Enhanced TSSOP-EP Package

MAX5068

High-Frequency, Current-Mode PWM Controller

with Accurate Programmable Oscillator

________________________________________________________________ Maxim Integrated Products 1

16

15

14

13

12

11

10

9

1

2

3

4

5

6

7

8

RT

REG5

IN

V

CC

NDRV

AGND

PGND

AGND

CS

TOP VIEW

MAX5068A/B

TSSOP-EP

SYNC

HYST

FB

DT

UVLO/EN

COMP

FLTINT

Pin Configurations

Ordering Information

19-3176; Rev 0; 2/04

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.

*Future product—contact factory for availability.
**EP = Exposed pad.

PART TEMP RANGE PIN-PACKAGE

MAX5068AAUE*

16 TSSOP-EP**

MAX5068BAUE

16 TSSOP-EP**

MAX5068CAUE

16 TSSOP-EP**

MAX5068DAUE*

16 TSSOP-EP**

MAX5068EAUE*

16 TSSOP-EP**

MAX5068FAUE*

16 TSSOP-EP**

Pin Configurations continued at end of data sheet.

Selector Guide appears at end of data sheet.

-40°C to +125°C

-40°C to +125°C

-40°C to +125°C

-40°C to +125°C

-40°C to +125°C

-40°C to +125°C

MAX5068

High-Frequency, Current-Mode PWM Controller
with Accurate Programmable Oscillator

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(V

IN

= +12V for the MAX5068B/E/F; VIN= +23.6V for the MAX5068A/C/D at startup, then reduces to +12V; CIN= C

REG5

= 0.1µF;

C

VCC

= 1µF; RRT= 100kΩ; NDRV = floating; TA= T

MIN

to T

MAX

, unless otherwise noted. Typical values are at TA= +25°C.) (Note 1)

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.

IN to PGND ............................................................-0.3V to +30V

IN to AGND.............................................................-0.3V to +30V

V

CC

to PGND..........................................................-0.3V to +13V

V

CC

to AGND..........................................................-0.3V to +13V

FB, COMP, CS, HYST, SYNC, REG5 to AGND ........-0.3V to +6V

UVLO/EN, RT, DT, SCOMP, FLTINT to AGND .........-0.3V to +6V

NDRV to PGND...........................................-0.3V to (V

CC

+ 0.3V)

AGND to PGND.....................................................-0.3V to +0.3V

Continuous Power Dissipation

16-Pin TSSOP-EP (derate 21.3mW/°C above +70°C)...1702mW

Operating Temperature Range..........................-40°C to +125°C

Maximum Junction Temperature .....................................+150°C

Storage Temperature Range .............................-60°C to +150°C

Lead Temperature (soldering, 10s) .................................+300°C

PARAMETER

CONDITIONS

UNITS

UNDERVOLTAGE LOCKOUT/STARTUP

Bootstrap UVLO Wake-Up Level

V

SUVR

VIN rising, MAX5068A/C/D only

V

Bootstrap UVLO Shutdown Level

V

SUVF

VIN falling, MAX5068A/C/D only

V

UVLO/EN Wake-Up Threshold V

ULR2

V

UVLO/EN

rising

V

UVLO/EN Shutdown Threshold V

ULF2

V

UVLO/EN

falling

V

HYST FET On-Resistance

MAX5068A/B/D/F only, sinking 50mA,
V

UVLO/EN

= 0V

Ω

HYST FET Leakage Current I

LEAK_HVUVLO/EN

= 2V, V

HYST

= 5V 3 nA

IN Supply Current In
Undervoltage Lockout

I

START

VIN = +19V, V

UVLO/EN

< V

ULF2

90 µA

IN Range V

IN

V

INTERNAL SUPPLIES (VCC and REG5)

VCC Regulator Set Point V

CCSP

V

REG5 Output Voltage V

REG5IREG5

= 0 to 1mA

V

REG5 Short-Circuit Current Limit

mA

f

SW

= 1.25MHz 5

IN Supply Current After Startup I

IN

VIN = +24V

f

SW

= 100kHz

mA

Shutdown Supply Current I

IN_SD

90 µA

GATE DRIVER (NDRV)

)

NDRV sinking 100mA 2 4

Driver Output Impedance

)

NDRV sourcing 25mA 3 6

Ω

Sinking

Driver Peak Output Current I

NDRV

Sourcing

mA

PWM COMPARATOR

Comparator Offset Voltage

V

COMP

- V

CS

V

Comparator Propagation Delay

VCS = 0.1V

ns

Minimum On-Time

)

Includes t

CS_BLANK

ns

CURRENT-LIMIT COMPARATOR

Current-Limit Trip Threshold V

CS

mV

SYMBOL

MIN TYP MAX

19.68 21.6 23.60

9.05 9.74 10.43

1.205 1.230 1.255

1.18

R

D S ( ON ) _H

Z

Z

V

I

REG5_SC

OUT(LOW

OUT(HIGH

OS_PWM

t

PD_PWM

t

ON(MIN

V

= + 10.8V to + 24V , V

IN

10.8 24.0

sour ci ng 1µA to 25m A 7.0 10.5

C C

4.85 5.00 5.15

1.30 1.60 2.00

298 314 330

10

47

18

2.5

1000

650

40

110

MAX5068

High-Frequency, Current-Mode PWM Controller

with Accurate Programmable Oscillator

_______________________________________________________________________________________ 3

PARAMETER

CONDITIONS

UNITS

CS Input Bias Current I

B_CS

VCS = 0V 0

µA

CS Blanking Time

ns

Propagation Delay from
Comparator Input to NDRV

50mV overdrive

ns

IN CLAMP VOLTAGE

IN Clamp Voltage

VIN sinking 2mA (Note 2)

V

ERROR AMPLIFIER (FB, COMP)

Voltage Gain A

V

R

COMP

= 100kΩ to AGND

dB

Unity-Gain Bandwidth BW

R

COMP

= 100kΩ to AGND,

C

LOAD

= 100pF to AGND

5

MHz

Phase Margin PM

R

COMP

= 100kΩ to AGND,

C

LOAD

= 100pF to AGND

degrees

FB Input Offset Voltage V

OS_FB

3mV

High

COMP Clamp Voltage V

COMP

Low

V

Error-Amplifier Output Current I

COMP

Sinking or sourcing

mA

+25°C † TA † +125°C (Note 3)

Reference Voltage V

REF

-40°C † TA † +125°C

V

Input Bias Current I

B_EA

nA

COMP Short-Circuit Current

mA

THERMAL SHUTDOWN

Thermal-Shutdown Temperature

T

SD

°C

Thermal Hysteresis T

HYST

°C

OSCILLATOR SYNC INPUT (MAX5068A/B/C/E Only)

SYNC High-Level Voltage

V

SYNC Low-Level Voltage

V

SYNC Input Bias Current

nA

Maximum SYNC Frequency f

SYNC

f

OSC

= 2.5MHz (Note 4)

MHz

SYNC High-Level Pulse Width

ns

SYNC Low-Level Pulse Width

ns

DIGITAL SOFT-START

Soft-Start Duration t

SS

(Note 5)

cycles

Reference-Voltage Step V

STEP

mV

Reference-Voltage Steps During
Soft-Start

steps

OSCILLATOR

Internal Oscillator Frequency
Range

f

OSC

f

OSC

= (10

11

/ R

RT

)

kHz

ELECTRICAL CHARACTERISTICS (continued)

(V

IN

= +12V for the MAX5068B/E/F; VIN= +23.6V for the MAX5068A/C/D at startup, then reduces to +12V; CIN= C

REG5

= 0.1µF;

C

VCC

= 1µF; RRT= 100kΩ; NDRV = floating; TA= T

MIN

to T

MAX

, unless otherwise noted. Typical values are at TA= +25°C.) (Note 1)

SYMBOL

t

CS_BLANK

V

I

V

t

IN_CLAMP

COMP_SC

IH_SYNC

V

IL_SYNC

I

B_SYNC

t

SYNC_HI

SYNC_LO

MIN TYP MAX

+2

70

40

24.0 26.0 29.0

80

65

2.6 3.8

0.4 1.1

0.5

1.215 1.230 1.245

1.205 1.230 1.242
100 300

12

+170

+25

10

0.4

2.4

3.125

30
30

2047

9.7

127

50 2500

MAX5068

High-Frequency, Current-Mode PWM Controller
with Accurate Programmable Oscillator

4 _______________________________________________________________________________________

Note 1: The MAX5068 is 100% tested at TA= +25°C. All limits over temperature are guaranteed by design.
Note 2: The MAX5068A/B are intended for use in universal-input power supplies. The internal clamp circuit is used to prevent the

bootstrap capacitor (C1 in Figure 1) from charging to a voltage beyond the absolute maximum rating of the device when
UVLO/EN is low. The maximum current to V

IN

(hence to clamp) when UVLO is low (device is in shutdown) must be external­ly limited to 2mA. Clamp currents higher than 2mA may result in clamp voltages higher than 30V, thus exceeding the
absolute maximum rating for V

IN

. For the MAX5068C/D, do not exceed the 24V maximum operating voltage of the device.

Note 3: Reference voltage (V

REF

) is measured with FB connected to COMP (see the Functional Diagram).

Note 4: The SYNC frequency must be at least 25% higher than the programmed oscillator frequency.
Note 5: The internal oscillator clock cycle.
Note 6: The MAX5068A/B driver switching frequency is one-half of the oscillator frequency. The MAX5068C/D/E/F driver switching

frequency is one-quarter of the oscillator frequency.

PARAMETER

SYMBOL

CONDITIONS

MIN

TYP

MAX

UNITS

fSW = 1011/(2 x RRT),
MAX5068A/B

kHz

NDRV Switching Frequency f

SW

(Note 6)

f

SW

= 1011/(4 x RRT),

MAX5068C/D/E/F

kHz

RT Voltage V

RT

40kΩ < R

RT

< 500kΩ

V

f

OSC

≤ 500kHz

TA = +25°C

f

OSC

> 500kHz -4

f

OSC

≤ 500kHz

Oscillator Accuracy

f

OSC

> 500kHz -6

%

MAX5068A/B

Maximum Duty Cycle D

MAX

DT connected to
REG5

MAX5068C/D/E/F

%

DEAD-TIME CONTROL (DT)

Dead Time t

DT

RDT = 24.9kΩ

ns

Dead-Time Disable Voltage

V

REG5

V

Dead-Time Regulation Voltage V

DT

V

INTEGRATING FAULT PROTECTION (FLTINT)

FLTINT Source Current I

FLTINT

V

FLTINT

= 0

µA

FLTINT Shutdown Threshold

V

FLTINT

rising

V

FLTINT Restart Threshold

V

FLTINT

falling

V

SLOPE COMPENSATION (SCOMP) MAX5068C/D/E/F Only

Slope Compensation V

SLOPE

C

SLOPE

= 100pF, RRT = 110kΩ

mV/µs

Slope-Compensation Range

090

mV/µs

Slope-Compensation Voltage
Range

0

V

ELECTRICAL CHARACTERISTICS (continued)

(V

IN

= +12V for the MAX5068B/E/F; VIN= +23.6V for the MAX5068A/C/D at startup, then reduces to +12V; CIN= C

REG5

= 0.1µF;

C

VCC

= 1µF; RRT= 100kΩ; NDRV = floating; TA= T

MIN

to T

MAX

, unless otherwise noted. Typical values are at TA= +25°C.) (Note 1)

V

D T_D IS ABLE

TA = - 40° C to + 125° C

25 1250

12.5 625

2.0

-2.5 +2.5

-4.5 +4.5

50
75

60

- 0.5V

1.23

+4

+6

V

FLTINT_SD

V

FLTINT_RS

V

SLOPER

V

SCOMP

60

2.8

1.6

15

2.7

MAX5068

High-Frequency, Current-Mode PWM Controller

with Accurate Programmable Oscillator

_______________________________________________________________________________________ 5

BOOTSTRAP UVLO WAKE-UP LEVEL

vs. TEMPERATURE

MAX5068 toc01

TEMPERATURE (°C)

V

IN

(V)

85603510-15

21.1

21.2

21.3

21.4

21.5

21.6

21.0

-40 110

MAX5068A/C/D

BOOTSTRAP UVLO SHUTDOWN LEVEL

vs. TEMPERATURE

MAX5068 toc02

TEMPERATURE (°C)

V

IN

(V)

85603510-15

9.6

9.7

9.8

9.9

10.0

9.5

-40 110

VIN FALLING
MAX5068A/C/D

UVLO/EN WAKE-UP THRESHOLD

vs. TEMPERATURE

MAX5068 toc03

TEMPERATURE (°C)

UVLO/EN (V)

85603510-15

1.225

1.230

1.235

1.240

1.245

1.220

-40 110

UVLO/EN RISING

UVLO/EN SHUTDOWN THRESHOLD

vs. TEMPERATURE

MAX5068 toc04

TEMPERATURE (°C)

UVLO/EN (V)

85603510-15

1.12

1.11

1.14

1.13

1.16

1.15

1.18

1.17

1.19

1.20

1.10

-40 110

UVLO/EN FALLING

VIN SUPPLY CURRENT IN

UNDERVOLTAGE LOCKOUT vs. TEMPERATURE

MAX5068 toc05

TEMPERATURE (°C)

I

START

(µA)

85603510-15

44

48

52

56

60

40

-40 110

VIN = 19V
WHEN IN BOOTSTRAP UVLO (MAX5068A/C/D)
UVLO/EN (MAX5068B/E/F) IS LOW

VIN SUPPLY CURRENT AFTER STARTUP

vs. TEMPERATURE

MAX5068 toc06

TEMPERATURE (°C)

I

IN

(mA)

85603510-15

2

3

4

5

6

1

-40 110

VIN = 24V

fSW = 1.25MHz

fSW = 500kHz

fSW = 250kHz

fSW = 100kHz

fSW = 50kHz

VCC vs. TEMPERATURE

MAX5068 toc07

TEMPERATURE (°C)

V

CC

(V)

85603510-15

7.6

7.3

8.2

7.9

8.8

8.5

9.4

9.1

9.7

10.0

7.0

-40 110

VIN = 19V, IIN = 25mA

VIN = 19V, IIN = 10mA

VIN = 10.8V, IIN = 10mA

VIN = 10.8V, IIN = 25mA

REG5 OUTPUT VOLTAGE

vs. OUTPUT CURRENT

MAX5068 toc08

OUTPUT CURRENT (mA)

REG5 (V)

1.81.61.41.21.00.80.60.40.2

4.955

4.960

4.965

4.970

4.975

4.980

4.950
0 2.0

RRT = 100kΩ

REG5 vs. TEMPERATURE

MAX5068 toc09

TEMPERATURE (°C)

REG5 (V)

85603510-15

4.92

4.91

4.94

4.93

4.96

4.95

4.98

4.97

4.99

5.00

4.90

-40 110

VIN = 10.8V

100µA LOAD

1mA LOAD

Typical Operating Characteristics

(V

IN

= +12V for the MAX5068B/E/F; VIN= +23.6V for MAX5068A/C/D at startup, then reduces to +12V; CIN= C

REG5

= 0.1µF;

C

VCC

= 1µF; RRT= 100kΩ; NDRV = floating; VFB= 0; V

COMP

= floating; VCS= 0; TA= +25°C, unless otherwise noted.)

MAX5068

High-Frequency, Current-Mode PWM Controller
with Accurate Programmable Oscillator

6 _______________________________________________________________________________________

Typical Operating Characteristics (continued)

(V

IN

= +12V for the MAX5068B/E/F; VIN= +23.6V for MAX5068A/C/D at startup, then reduces to +12V; CIN= C

REG5

= 0.1µF;

C

VCC

= 1µF; RRT= 100kΩ; NDRV = floating; VFB= 0; V

COMP

= floating; VCS= 0; TA= +25°C, unless otherwise noted.)

REG5 OUTPUT VOLTAGE vs. V

IN

MAX5068 toc10

VIN (V)

REG5 (V)

222016 18141210 24

4.976

4.977

4.978

4.979

4.980

4.981

4.982

4.983

4.984

4.985

4.975

I

REG5

= 100µA

CS TRIP THRESHOLD

vs. TEMPERATURE

MAX5068 toc11

TEMPERATURE (°C)

CS TRIP THRESHOLD (mV)

110

85603510-15

306

303

309

315

312

321

318

327
324

330

300

-40

SWITCHING FREQUENCY

vs. TEMPERATURE

MAX5068 toc12

TEMPERATURE (°C)

SWITCHING FREQUENCY (kHz)

110

856035-15

10

480

475

485

495

490

505

500

515
510

520

470

-40

fSW = 500kHz

TOTAL NUMBER OF
DEVICES = 200

MEAN

-3σ

+3σ

PROPAGATION DELAY FROM CS COMPARATOR

INPUT TO NDRV vs. TEMPERATURE

MAX5068 toc13

TEMPERATURE (°C)

PROPAGATION DELAY (ns)

1108535 6010-15

32

34

36

38

40

42

44

46

48

50

30

-40

INPUT CURRENT

vs. INPUT CLAMP VOLTAGE

MAX5068 toc14

INPUT CLAMP VOLTAGE (V)

INPUT CURRENT (mA)

27.525.022.520.017.515.012.5

2

4

6

8

10

12

14

0

10.0 30.0

INPUT CLAMP VOLTAGE

vs. TEMPERATURE

MAX5068 toc15

TEMPERATURE (°C)

INPUT CLAMP VOLTAGE (V)

1108535 6010-15

25.2

25.4

25.6

25.8

26.0

26.2

26.4

26.6

26.8

27.0

25.0

-40

I

SINK

= 2mA

NDRV OUTPUT IMPEDANCE

vs. TEMPERATURE

MAX5068 toc16

TEMPERATURE (°C)

R

ON

(Ω)

85603510-15

1.4

1.2

1.8

1.6

2.2

2.0

2.6

2.4

2.8

3.0

1.0

-40 110

VIN = 24V
SINKING 100mA

NDRV OUTPUT IMPEDANCE

vs. TEMPERATURE

MAX5068 toc17

TEMPERATURE (°C)

R

ON

(Ω)

85603510-15

2.4

2.2

2.8

2.6

3.2

3.0

3.6

3.4

3.8

4.0

2.0

-40 110

VIN = 24V
SOURCING 25mA

ERROR AMPLIFIER OPEN-LOOP GAIN

AND PHASE vs. FREQUENCY

MAX5068 toc18

FREQUENCY (Hz)

GAIN (dB)

PHASE (DEGREES)

10M10 100k1k

-20

0

20

40

60

80

100

120

-40

-180

-150

-120

-90

-60

-30

0

30

-210

0.1

GAIN

PHASE