19-3176; Rev 1; 7/04
High-Frequency, Current-Mode PWM Controller
with Accurate Programmable Oscillator
General Description
The MAX5068 is a high-frequency, current-mode,
pulse-width modulation (PWM) controller that integrates
all the building blocks necessary for implementing AC-
DC 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 sim-
plifies control-loop design, and a programmable inter-
nal 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 programma-
ble oscillator that simplifies system design.
An input undervoltage lockout (UVLO) programs the
input-supply startup voltage and ensures proper opera-
tion 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.
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 85V
AC
to 265V
AC
or 36V
DC
to 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
Ordering Information
PART
MAX5068AAUE
MAX5068BAUE
MAX5068CAUE
MAX5068DAUE
MAX5068EAUE
MAX5068FAUE
*EP
= Exposed pad.
TEMP RANGE
-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
PIN-PACKAGE
16 TSSOP-EP*
16 TSSOP-EP*
16 TSSOP-EP*
16 TSSOP-EP*
16 TSSOP-EP*
16 TSSOP-EP*
Applications
Universal-Input AC Power Supplies
Isolated Telecom Power Supplies
Networking System Power Supplies
Server Power Supplies
Industrial Power Conversion
TOP VIEW
RT 1
SYNC 2
HYST 3
DT 4
UVLO/EN 5
FB 6
COMP 7
FLTINT 8
Pin Configurations
16 REG5
15 IN
14 V
CC
MAX5068A/B
13 NDRV
12 AGND
11 PGND
10 AGND
9
CS
Selector Guide appears at end of data sheet.
TSSOP-EP
Pin Configurations continued at end of data sheet.
1
________________________________________________________________
Maxim Integrated Products
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.
High-Frequency, Current-Mode PWM Controller
with Accurate Programmable Oscillator
MAX5068
ABSOLUTE MAXIMUM RATINGS
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
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.
ELECTRICAL CHARACTERISTICS
(V
IN
= +12V for the MAX5068B/E/F; V
IN
= +23.6V for the MAX5068A/C/D at startup, then reduces to +12V; C
IN
= C
REG5
= 0.1µF;
C
VCC
= 1µF; R
RT
= 100kΩ; NDRV = floating; T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
Bootstrap UVLO Wake-Up Level
Bootstrap UVLO Shutdown Level
UVLO/EN Wake-Up Threshold
UVLO/EN Shutdown Threshold
HYST FET On-Resistance
HYST FET Leakage Current
IN Supply Current In
Undervoltage Lockout
IN Range
V
CC
Regulator Set Point
REG5 Output Voltage
REG5 Short-Circuit Current Limit
IN Supply Current After Startup
Shutdown Supply Current
GATE DRIVER (NDRV)
Driver Output Impedance
Driver Peak Output Current
PWM COMPARATOR
Comparator Offset Voltage
Comparator Propagation Delay
Minimum On-Time
CURRENT-LIMIT COMPARATOR
Current-Limit Trip Threshold
V
CS
298
314
330
mV
V
OS_PWM
t
PD_PWM
t
ON(MIN)
V
COMP
- V
CS
V
CS
= 0.1V
Includes t
CS_BLANK
1.30
1.60
40
110
2.00
V
ns
ns
Z
OUT(LOW)
NDRV sinking 100mA
Sinking
Sourcing
2
3
1000
650
4
6
Z
OUT(HIGH)
NDRV sourcing 25mA
I
NDRV
Ω
mA
SYMBOL
V
SUVR
V
SUVF
V
ULR2
V
ULF2
R
DS(ON)_H
I
LEAK_H
I
START
V
IN
V
CCSP
V
REG5
I
REG5_SC
I
IN
I
IN_SD
V
IN
= +24V
f
SW
= 1.25MHz
f
SW
= 100kHz
V
IN
= +10.8V to +24V, V
CC
sourcing 1µA to 25mA
I
REG5
= 0 to 1mA
CONDITIONS
V
IN
rising, MAX5068A/C/D only
V
IN
falling, MAX5068A/C/D only
V
UVLO/EN
rising
V
UVLO/EN
falling
MAX5068A/B/D/F only, sinking 50mA,
V
UVLO/EN
= 0V
V
UVLO/EN
= 2V, V
HYST
= 5V
V
IN
= +19V, V
UVLO/EN
< V
ULF2
10.8
7.0
4.85
5.00
18
5
2.5
90
MIN
19.68
9.05
1.205
TYP
21.6
9.74
1.230
1.18
10
3
47
90
24.0
10.5
5.15
MAX
23.60
10.43
1.255
UNITS
V
V
V
V
Ω
nA
µA
V
V
V
mA
mA
µA
UNDERVOLTAGE LOCKOUT/STARTUP
INTERNAL SUPPLIES (V
CC
and REG5)
2
_______________________________________________________________________________________
High-Frequency, Current-Mode PWM Controller
with Accurate Programmable Oscillator
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= +12V for the MAX5068B/E/F; V
IN
= +23.6V for the MAX5068A/C/D at startup, then reduces to +12V; C
IN
= C
REG5
= 0.1µF;
C
VCC
= 1µF; R
RT
= 100kΩ; NDRV = floating; T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
CS Input Bias Current
CS Blanking Time
Propagation Delay from
Comparator Input to NDRV
IN CLAMP VOLTAGE
IN Clamp Voltage
ERROR AMPLIFIER (FB, COMP)
Voltage Gain
Unity-Gain Bandwidth
Phase Margin
FB Input Offset Voltage
COMP Clamp Voltage
Error-Amplifier Output Current
Reference Voltage
Input Bias Current
COMP Short-Circuit Current
THERMAL SHUTDOWN
Thermal-Shutdown Temperature
Thermal Hysteresis
SYNC High-Level Voltage
SYNC Low-Level Voltage
SYNC Input Bias Current
Maximum SYNC Frequency
SYNC High-Level Pulse Width
SYNC Low-Level Pulse Width
DIGITAL SOFT-START
Soft-Start Duration
Reference-Voltage Step
Reference-Voltage Steps During
Soft-Start
OSCILLATOR
Internal Oscillator Frequency
Range
f
OSC
f
OSC
= (10
11
/ R
RT
)
50
2500
kHz
t
SS
V
STEP
(Note 5)
2047
9.7
127
cycles
mV
steps
T
SD
T
HYST
V
IH_SYNC
V
IL_SYNC
I
B_SYNC
f
SYNC
t
SYNC_HI
t
SYNC_LO
f
OSC
= 2.5MHz (Note 4)
3.125
30
30
10
2.4
0.4
+170
+25
°C
°C
V
V
nA
MHz
ns
ns
A
V
BW
PM
V
OS_FB
V
COMP
I
COMP
V
REF
I
B_EA
I
COMP_SC
High
Low
Sinking or sourcing
+25°C
≤
T
A
≤
+125°C (Note 3)
-40°C
≤
T
A
≤
+125°C
2.6
0.4
0.5
1.215
1.205
1.230
1.230
100
12
1.245
1.242
300
R
COMP
= 100kΩ to AGND
R
COMP
= 100kΩ to AGND,
C
LOAD
= 100pF to AGND
R
COMP
= 100kΩ to AGND,
C
LOAD
= 100pF to AGND
80
5
65
3
3.8
1.1
dB
MHz
degrees
mV
V
mA
V
nA
mA
V
IN_CLAMP
V
IN
sinking 2mA (Note 2)
24.0
26.0
29.0
V
SYMBOL
I
B_CS
t
CS_BLANK
50mV overdrive
V
CS
= 0V
CONDITIONS
MIN
0
70
40
TYP
MAX
+2
UNITS
µA
ns
ns
MAX5068
OSCILLATOR SYNC INPUT (MAX5068A/B/C/E Only)
_______________________________________________________________________________________
3
High-Frequency, Current-Mode PWM Controller
with Accurate Programmable Oscillator
MAX5068
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= +12V for the MAX5068B/E/F; V
IN
= +23.6V for the MAX5068A/C/D at startup, then reduces to +12V; C
IN
= C
REG5
= 0.1µF;
C
VCC
= 1µF; R
RT
= 100kΩ; NDRV = floating; T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
f
SW
= 10
11
/(2 x R
RT
),
MAX5068A/B
NDRV Switching Frequency
f
SW
(Note 6)
f
SW
= 10
11
/(4 x R
RT
),
MAX5068C/D/E/F
f
OSC
≤
500kHz
f
OSC
> 500kHz
f
OSC
≤
500kHz
f
OSC
> 500kHz
MAX5068A/B
MAX5068C/D/E/F
MIN
25
12.5
2.0
-2.5
-4
-4.5
-6
50
75
60
V
REG5
- 0.5V
1.23
V
FLTINT
= 0
60
2.8
1.6
15
0
0
90
2.7
+2.5
+4
+4.5
+6
%
%
TYP
MAX
1250
625
UNITS
kHz
kHz
V
RT Voltage
V
RT
40kΩ < R
RT
< 500kΩ
T
A
= +25°C
Oscillator Accuracy
T
A
= -40°C to +125°C
Maximum Duty Cycle
DEAD-TIME CONTROL (DT)
Dead Time
Dead-Time Disable Voltage
Dead-Time Regulation Voltage
FLTINT Source Current
FLTINT Shutdown Threshold
FLTINT Restart Threshold
Slope Compensation
Slope-Compensation Range
Slope-Compensation Voltage
Range
t
DT
V
DT_DISABLE
V
DT
I
FLTINT
R
DT
= 24.9kΩ
D
MAX
DT connected to
REG5
ns
V
V
µA
V
V
mV/µs
mV/µs
V
INTEGRATING FAULT PROTECTION (FLTINT)
V
FLTINT_SD
V
FLTINT
rising
V
FLTINT_RS
V
FLTINT
falling
SLOPE COMPENSATION (SCOMP) MAX5068C/D/E/F Only
V
SLOPE
V
SLOPER
V
SCOMP
C
SLOPE
= 100pF, R
RT
= 110kΩ
Note 1:
The MAX5068 is 100% tested at T
A
= +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 external-
ly 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.
4
_______________________________________________________________________________________
High-Frequency, Current-Mode PWM Controller
with Accurate Programmable Oscillator
Typical Operating Characteristics
(V
IN
= +12V for the MAX5068B/E/F; V
IN
= +23.6V for MAX5068A/C/D at startup, then reduces to +12V; C
IN
= C
REG5
= 0.1µF;
C
VCC
= 1µF; R
RT
= 100kΩ; NDRV = floating; V
FB
= 0; V
COMP
= floating; V
CS
= 0; T
A
= +25°C, unless otherwise noted.)
BOOTSTRAP UVLO WAKE-UP LEVEL
vs. TEMPERATURE
MAX5068 toc01
MAX5068
BOOTSTRAP UVLO SHUTDOWN LEVEL
vs. TEMPERATURE
MAX5068 toc02
UVLO/EN WAKE-UP THRESHOLD
vs. TEMPERATURE
UVLO/EN RISING
MAX5068 toc03
21.6
MAX5068A/C/D
21.5
21.4
V
IN
(V)
21.3
21.2
21.1
21.0
-40
-15
10
35
60
85
110
TEMPERATURE (°C)
10.0
V
IN
FALLING
MAX5068A/C/D
9.9
1.245
1.240
UVLO/EN (V)
V
IN
(V)
9.8
1.235
9.7
1.230
9.6
1.225
9.5
-40
-15
10
35
60
85
110
TEMPERATURE (°C)
1.220
-40
-15
10
35
60
85
110
TEMPERATURE (°C)
UVLO/EN SHUTDOWN THRESHOLD
vs. TEMPERATURE
MAX5068 toc04
V
IN
SUPPLY CURRENT IN
UNDERVOLTAGE LOCKOUT vs. TEMPERATURE
MAX5068 toc05
VIN SUPPLY CURRENT AFTER STARTUP
vs. TEMPERATURE
V
IN
= 24V
f
SW
= 1.25MHz
5
MAX5068 toc06
1.20
1.19
1.18
1.17
UVLO/EN (V)
UVLO/EN FALLING
60
56
V
IN
= 19V
WHEN IN BOOTSTRAP UVLO (MAX5068A/C/D)
UVLO/EN (MAX5068B/E/F) IS LOW
6
I
IN
(mA)
1.16
1.15
1.14
1.13
1.12
1.11
1.10
-40
-15
10
35
60
85
110
TEMPERATURE (°C)
I
START
(µA)
52
4
f
SW
= 500kHz
f
SW
= 250kHz
48
3
44
2
f
SW
= 100kHz
f
SW
= 50kHz
35
60
85
110
40
-40
-15
10
35
60
85
110
TEMPERATURE (°C)
1
-40
-15
10
TEMPERATURE (°C)
V
CC
vs. TEMPERATURE
MAX5068 toc07
REG5 OUTPUT VOLTAGE
vs. OUTPUT CURRENT
MAX5068 toc08
REG5 vs. TEMPERATURE
4.99
4.98
4.97
REG5 (V)
4.96
4.95
4.94
1mA LOAD
V
IN
= 10.8V
100µA LOAD
MAX5068 toc09
10.0
9.7
9.4
9.1
V
IN
= 19V, I
IN
= 25mA
V
IN
= 19V, I
IN
= 10mA
4.980
R
RT
= 100kΩ
4.975
4.970
REG5 (V)
4.965
4.960
5.00
V
CC
(V)
8.8
8.5
8.2
7.9
7.6
7.3
7.0
-40
-15
10
35
60
85
110
TEMPERATURE (°C)
V
IN
= 10.8V, I
IN
= 25mA
V
IN
= 10.8V, I
IN
= 10mA
4.93
4.92
4.91
4.955
4.950
0
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
OUTPUT CURRENT (mA)
4.90
-40
-15
10
35
60
85
110
TEMPERATURE (°C)
_______________________________________________________________________________________
5
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