19-3175; Rev 1; 7/04
High-Frequency, Current-Mode PWM Controller
with Accurate Oscillator and Dual FET Drivers
The MAX5069 is a high-frequency, current-mode,
pulse-width modulation (PWM) controller (with dual
MOSFET drivers) that integrates all the building blocks
necessary for implementing AC-DC or DC-DC fixed-frequency power supplies. Isolated or nonisolated pushpull and half/full-bridge 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%.
An input undervoltage lockout (UVLO) programs the
input-supply startup voltage and ensures proper operation during brownout conditions.
A single external resistor programs the oscillator frequency from 50kHz to 2.5MHz. The MAX5069A/D provide a
SYNC input for synchronization to an external clock. The
maximum FET-driver duty cycle for the MAX5069 is 50%.
Programmable dead time allows additional flexibility in
optimizing magnetic design and overcoming parasitic
effects. Programmable hiccup current limit provides
additional protection under severe faults.
The MAX5069 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 MAX5068 data sheet for single FET-driver applications.
Warning: The MAX5069 is designed to work with high
voltages. Exercise caution.
Features
♦ Current-Mode Control with 47µA (typ) Startup
Current
♦ Oscillator Frequency Programmable to 2.5MHz
♦ Resistor-Programmable ±4.5% Accurate
Switching Frequency
♦ Dual Gate-Drive Output for Half/Full-Bridge or
Push-Pull Applications
♦ Rectified 85VAC to 265VAC, or 36VDC to 72VDC
Input (MAX5069A/B)
♦ Input Directly Driven from 10.8V to 24V
(MAX5069C/D)
♦ Programmable Dead Time and Slope
Compensation
♦ Programmable Startup Voltage (UVLO)
♦ Programmable UVLO Hysteresis (MAX5069B/C)
♦ Frequency Synchronization Input (MAX5069A/D)
♦ -40°C to +125°C Automotive Temperature Range
♦ 16-Pin Thermally Enhanced TSSOP-EP Package
Ordering Information
TEMP RANGE
PIN-PACKAGE
MAX5069AAUE
PART
-40°C to +125°C
16 TSSOP-EP*
MAX5069BAUE
-40°C to +125°C
16 TSSOP-EP*
MAX5069CAUE
-40°C to +125°C
16 TSSOP-EP*
MAX5069DAUE
-40°C to +125°C
16 TSSOP-EP*
*EP = Exposed pad.
Applications
Universal-Input AC Power Supplies
Pin Configuration
Isolated Telecom Power Supplies
Networking System Power Supplies
TOP VIEW
Server Power Supplies
Industrial Power Conversion
RT 1
16 REG5
SYNC(HYST*) 2
15 IN
SCOMP 3
DT 4
14 VCC
MAX5069
13 NDRVA
12 NDRVB
UVLO/EN 5
FB 6
11 PGND
COMP 7
10 AGND
FLTINT 8
9
CS
TSSOP-EP
*MAX5069B/C.
Selector Guide appears at end of data sheet.
________________________________________________________________ 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.
1
MAX5069
General Description
MAX5069
High-Frequency, Current-Mode PWM Controller
with Accurate Oscillator and Dual FET Drivers
ABSOLUTE MAXIMUM RATINGS
IN to PGND ............................................................-0.3V to +30V
IN to AGND.............................................................-0.3V to +30V
VCC to PGND..........................................................-0.3V to +13V
VCC 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
NDRVA, NDRVB to PGND ..........................-0.3V to (VCC + 0.3V)
AGND to PGND .....................................................-0.3V to +0.3V
Continuous Power Dissipation (TA = +70°C)
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
(VIN = +12V for the MAX5069C/D, VIN = +23.6V for the MAX5069A/B at startup, then reduces to +12V, CIN = CREG5 = 0.1µF,
CVCC = 1µF, RRT = 100kΩ, NDRV_ = floating, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
UNDERVOLTAGE LOCKOUT/STARTUP
Bootstrap UVLO Wake-Up Level
VSUVR
VIN rising, MAX5069A/B
19.68
21.6
23.60
V
Bootstrap UVLO Shutdown Level
VSUVF
VIN falling, MAX5069A/B
9.05
9.74
10.43
V
UVLO/EN Wake-Up Threshold
VULR2
UVLO/EN rising
1.205
1.230
1.255
V
UVLO/EN Shutdown Threshold
VULF2
UVLO/EN falling
HYST FET On-Resistance
RDS(ON)_H
1.18
V
MAX5069B/C only, sinking 50mA,
VUVLO/EN = 0V
10
Ω
nA
HYST FET Leakage Current
ILEAK_H
VUVLO/EN = 2V, VHYST = 5V
3
IN Supply Current In
Undervoltage Lockout
ISTART
VIN = +19V, VUVLO/EN < VULF2
47
IN Range
VIN
10.8
90
µA
24.0
V
10.5
V
INTERNAL SUPPLIES (VCC and REG5)
VCC Regulator Set Point
VCCSP
VIN = +10.8V to +24V, VCC sourcing 1µA to 25mA
7.0
REG5 Output Voltage
VREG5
IREG5 = 0 to 1mA
4.85
REG5 Short-Circuit Current Limit
IREG5_SC
IN Supply Current After Startup
IIN
Shutdown Supply Current
5.00
5.15
18
VIN = +24V
fSW = 1.25MHz
7
fSW = 100kHz
3
IVIN_SD
V
mA
mA
90
µA
GATE DRIVER (NDRVA, NDRVB)
Driver Output Impedance
Driver Peak Output Current
NDRVA/NDRVB sinking 100mA
2
4
ZOUT(HIGH) NDRVA/NDRVB sourcing 25mA
ZOUT(LOW)
3
6
INDRV
Sinking
1000
Sourcing
650
Ω
mA
PWM COMPARATOR
Comparator Offset Voltage
VOS_PWM
VCOMP > VCS
Comparator Propagation Delay
tPD_PWM
VCS = 0.1V
1.30
1.60
40
2.00
ns
V
Minimum On-Time
tON(MIN)
Includes tCS_BLANK
110
ns
CURRENT-LIMIT COMPARATOR
Current-Limit Trip Threshold
2
VCS
298
314
_______________________________________________________________________________________
330
mV
High-Frequency, Current-Mode PWM Controller
with Accurate Oscillator and Dual FET Drivers
(VIN = +12V for the MAX5069C/D, VIN = +23.6V for the MAX5069A/B at startup, then reduces to +12V, CIN = CREG5 = 0.1µF,
CVCC = 1µF, RRT = 100kΩ, NDRV_ = floating, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1)
PARAMETER
CS Input Bias Current
CS Blanking Time
SYMBOL
IB_CL
CONDITIONS
VCS = 0V
MIN
0
tCS_BLANK
Propagation Delay from
Comparator Input to NDRV_
tPD_CL
TYP
50mV overdrive
MAX
UNITS
+2
µA
70
ns
40
ns
IN CLAMP VOLTAGE
IN Clamp Voltage
VIN_CLAMP
IN sinking 2mA (Note 2)
24.0
26.0
29.0
V
ERROR AMPLIFIER (FB, COMP)
Voltage Gain
AV
RCOMP = 100kΩ to AGND
80
dB
Unity-Gain Bandwidth
BW
RCOMP = 100kΩ to AGND,
CLOAD = 100pF to AGND
5
MHz
Phase Margin
PM
RCOMP = 100kΩ to AGND,
CLOAD = 100pF to AGND
65
Degrees
FB Input Offset Voltage
VOS_FB
COMP Clamp Voltage
VCOMP
Error-Amplifier Output Current
ICOMP
3
High
2.6
3.8
Low
0.4
1.1
Sinking or sourcing
0.5
mV
V
mA
+25°C ≤ TA ≤ +125°C (Note 3)
1.215
1.230
1.245
-40°C ≤ TA ≤ +125°C (Note 3)
1.205
1.230
1.242
300
Reference Voltage
VREF
Input Bias Current
IB_EA
100
ICOMP_SC
12
mA
TSD
+170
°C
THYST
25
°C
COMP Short-Circuit Current
V
nA
THERMAL SHUTDOWN
Thermal-Shutdown Temperature
Thermal Hysteresis
OSCILLATOR SYNC INPUT (MAX5069A/D only)
SYNC High-Level Voltage
VIH_SYNC
SYNC Low-Level Voltage
VIL_SYNC
SYNC Input Bias Current
IB_SYNC
Maximum SYNC Frequency
fSYNC
2.4
V
0.4
10
fOSC = 2.5MHz (Note 4)
V
nA
3.125
MHz
SYNC High-Level Pulse Width
tSYNC_HI
30
ns
SYNC Low-Level Pulse Width
tSYNC_LO
30
ns
DIGITAL SOFT-START
Soft-Start Duration
tSS
Reference-Voltage Step
(Note 5)
VSTEP
Reference-Voltage Steps During
Soft-Start
2047
Cycles
9.7
mV
127
Steps
OSCILLATOR
Oscillator Frequency Range
fOSC
fOSC = (1011 / RRT)
50
2500
kHz
_______________________________________________________________________________________
3
MAX5069
ELECTRICAL CHARACTERISTICS (continued)
MAX5069
High-Frequency, Current-Mode PWM Controller
with Accurate Oscillator and Dual FET Drivers
ELECTRICAL CHARACTERISTICS (continued)
(VIN = +12V for the MAX5069C/D, VIN = +23.6V for the MAX5069A/B at startup, then reduces to +12V, CIN = CREG5 = 0.1µF,
CVCC = 1µF, RRT = 100kΩ, NDRV_ = floating, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
NDRV_ Switching Frequency
fSW
fSW = 1011 / (2 x RRT)
RT Voltage
VRT
40kΩ < RRT < 500kΩ
TA = +25°C
Oscillator Accuracy
TA = -40°C to +125°C
Maximum Duty Cycle
DMAX
MIN
TYP
25
MAX
UNITS
1250
kHz
2.0
V
fOSC ≤ 500kHz
-2.5
+2.5
fOSC > 500kHz
-4
+4
fOSC ≤ 500kHz
-4.5
+4.5
fOSC > 500kHz
-6
%
+6
DT connected to REG5
100
%
RDT = 24.9kΩ
60
ns
DEAD-TIME CONTROL (DT)
Dead Time
Dead-Time Disable Voltage
Dead-Time Regulation Voltage
tDT
VREG5 0.5V
VDT_DISABLE
VDT
V
1.23
V
INTEGRATING FAULT PROTECTION (FLTINT)
FLTINT Source Current
IFLTINT
VFLTINT = 0V
60
µA
FLTINT Shutdown Threshold
VFLTINT_SD
VFLTINT rising
2.8
V
FLTINT Restart Threshold
VFLTINT_RS
VFLTINT falling
1.6
V
CSLOPE = 100pf, RT = 110kΩ
15
mV/µs
SLOPE COMPENSATION
Slope Compensation
VSLOPE
Slope-Compensation Range
VSLOPER
0
90
mV/µs
Slope-Compensation Voltage
Range
VSCOMP
0
2.7
V
Note 1: The MAX5069 is 100% tested at TA = +25°C. All limits over temperature are guaranteed by design.
Note 2: The MAX5069A/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 VIN (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 VIN. For the MAX5069C/D, do not exceed the 24V maximum operating voltage of the device.
Note 3: Reference voltage (VREF) 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.
4
_______________________________________________________________________________________
High-Frequency, Current-Mode PWM Controller
with Accurate Oscillator and Dual FET Drivers
MAX5069A/B
21.5
UVLO/EN WAKE-UP THRESHOLD
vs. TEMPERATURE
MAX5069A/B
1.245
9.9
MAX5069 toc03
10.0
MAX5069 toc01
21.6
BOOTSTRAP UVLO SHUTDOWN LEVEL
vs. TEMPERATURE
MAX5069 toc02
BOOTSTRAP UVLO WAKE-UP LEVEL
vs. TEMPERATURE
UVLO/EN RISING
1.240
21.4
UVLO/EN (V)
VIN (V)
VIN (V)
9.8
21.3
9.7
1.235
1.230
21.2
9.6
21.0
9.5
10
35
60
85
110
1.220
-40
-15
10
35
60
85
110
-40
60
85
110
UVLO/EN SHUTDOWN THRESHOLD
vs. TEMPERATURE
VIN SUPPLY CURRENT IN UNDERVOLTAGE
LOCKOUT vs. TEMPERATURE
VIN SUPPLY CURRENT AFTER STARTUP
vs. TEMPERATURE
UVLO/EN FALLING
60
VIN = 19V
WHEN IN BOOTSTRAP UVLO (MAX5069A/B)
UVLO/EN (MAX5069C/D) IS LOW
56
8
fSW = 1.25MHz
VIN = 24V
7
6
1.15
1.14
52
IIN (mA)
1.16
ISTART (µA)
48
1.13
fSW = 500kHz
5
fSW = 250kHz
4
3
1.12
44
2
1.11
fSW = 100kHz
fSW = 50kHz
1.10
40
10
35
60
85
110
-15
10
35
60
85
TEMPERATURE (°C)
VCC vs. TEMPERATURE
REG5 OUTPUT VOLTAGE
vs. OUTPUT CURRENT
10.0
9.7
VIN = 19V, IIN = 10mA
VIN = 19V, IIN = 25mA
9.4
-40
TEMPERATURE (°C)
4.980
RRT = 100kΩ
4.975
9.1
110
-40
4.99
-40
-15
10
35
60
TEMPERATURE (°C)
85
110
100µA LOAD
1mA LOAD
4.95
4.94
4.92
4.955
4.91
4.90
4.950
7.0
110
4.93
VIN = 10.8V, IIN = 10mA
VIN = 10.8V, IIN = 25mA
85
VIN = 10.8V
4.96
4.965
4.960
7.3
60
4.97
8.2
7.6
35
4.98
REG5 (V)
REG5 (V)
8.5
10
REG5 vs. TEMPERATURE
5.00
4.970
8.8
-15
TEMPERATURE (°C)
MAX5069 toc08
-15
MAX5069 toc07
-40
1
MAX5069 toc09
UVLO/EN (V)
35
TEMPERATURE (°C)
1.17
VCC (V)
10
TEMPERATURE (°C)
1.18
7.9
-15
TEMPERATURE (°C)
MAX5069 toc05
1.19
-15
MAX5069 toc04
-40
1.20
1.225
MAX5069 toc06
21.1
0
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
OUTPUT CURRENT (mA)
-40
-15
10
35
60
85
110
TEMPERATURE (°C)
_______________________________________________________________________________________
5
MAX5069
Typical Operating Characteristics
(VIN = +23.6V for MAX5069A/B at startup, then reduces to +12V, VIN = +12V for the MAX5069C/D, CIN = CREG5 = 0.1µF, CVCC = 1µF,
RRT = 100kΩ, NDRV_ = floating, VFB = 0V, VCOMP = floating, VCS = 0V, TA = +25°C, unless otherwise noted.)
Typical Operating Characteristics (continued)
(VIN = +23.6V for MAX5069A/B at startup, then reduces to +12V, VIN = +12V for the MAX5069C/D, CIN = CREG5 = 0.1µF, CVCC = 1µF,
RRT = 100kΩ, NDRV_ = floating, VFB = 0V, VCOMP = floating, VCS = 0V, TA = +25°C, unless otherwise noted.)
CS TRIP THRESHOLD
vs. TEMPERATURE
4.982
4.981
4.980
4.979
4.978
318
315
312
309
fSW = 500kHz
525
+3σ
510
505
MEAN
500
-3σ
495
306
4.976
303
485
4.975
300
-40
480
-40
12
14
16
18
20
22
-15
10
35
60
85
490
110
10
-15
35
60
110
85
VIN (V)
TEMPERATURE (°C)
TEMPERATURE (°C)
PROPAGATION DELAY FROM CS COMPARATOR
INPUT TO NDRV vs. TEMPERATURE
INPUT CURRENT
vs. INPUT CLAMP VOLTAGE
INPUT CLAMP VOLTAGE
vs. TEMPERATURE
INPUT CURRENT (mA)
46
12
44
42
40
38
36
10
8
6
4
34
26.6
26.4
26.2
26.0
25.8
25.6
-40
-15
10
35
60
85
25.2
25.0
0
110
-40
10.0 12.5 15.0 17.5 20.0 22.5 25.0 27.5 30.0
-15
10
35
60
85
110
INPUT CLAMP VOLTAGE (V)
TEMPERATURE (°C)
NDRVA/NDRVB OUTPUT IMPEDANCE
vs. TEMPERATURE
NDRVA/NDRVB OUTPUT IMPEDANCE
vs. TEMPERATURE
ERROR AMPLIFIER OPEN-LOOP GAIN
AND PHASE vs. FREQUENCY
4.0
MAX5069 toc16
2.6
3.8
3.6
3.4
2.2
3.2
RON (Ω)
2.4
2.0
1.8
VIN = 24V
SOURCING 25mA
2.8
2.6
1.4
2.4
1.2
2.2
2.0
1.0
-40
-15
10
35
60
TEMPERATURE (°C)
85
110
100
-30
GAIN
-60
60
40
-90
PHASE
20
-120
0
-150
-20
-180
-40
-40
-15
10
35
60
TEMPERATURE (°C)
85
110
30
0
80
3.0
1.6
MAX5069 toc18
120
GAIN (dB)
VIN = 24V
SINKING 100mA
MAX5069 toc17
TEMPERATURE (°C)
-210
0.1
10
1k
100k
FREQUENCY (Hz)
_______________________________________________________________________________________
10M
PHASE (DEGREES)
30
2.8
ISINK = 2mA
26.8
25.4
2
32
3.0
27.0
MAX5069 toc15
48
INPUT CLAMP VOLTAGE (V)
14
MAX5069 toc13
50
PROPAGATION DELAY (ns)
24
TOTAL NUMBER OF
DEVICES = 200
520
515
4.977
10
6
530
MAX5069 toc12
324
321
MAX5069 toc14
REG5 (V)
327
CS TRIP THRESHOLD (mV)
4.983
MAX5069 toc11
IREG5 = 100µA
4.984
330
MAX5069 toc10
4.985
SWITCHING FREQUENCY
vs. TEMPERATURE
SWITCHING FREQUENCY (kHz)
REG5 OUTPUT VOLTAGE vs. VIN
RON (Ω)
MAX5069
High-Frequency, Current-Mode PWM Controller
with Accurate Oscillator and Dual FET Drivers
High-Frequency, Current-Mode PWM Controller
with Accurate Oscillator and Dual FET Drivers
VIN = 24V
SINKING 50mA
12.0
11.0
62.5
62.4
10.5
10.0
62.3
9.5
62.2
9.0
62.1
8.5
8.0
62.0
-15
10
35
60
85
-15
10
60
85
TEMPERATURE (°C)
TEMPERATURE (°C)
35
110
0.03
50.8
50.4
50.0
49.6
49.2
48.8
504
MAX5069 toc23
51.2
NDRV SWITCHING FREQUENCY (kHz)
fSW = 50kHz
1
2
NDRV SWITCHING FREQUENCY
vs. TEMPERATURE
505
MAX5069 toc22
52.0
0.1
RRT (MΩ)
NDRV SWITCHING FREQUENCY
vs. TEMPERATURE
NDRV SWITCHING FREQUENCY
vs. TEMPERATURE
51.6
0.1
0.01
-40
110
fSW = 500kHz
503
502
501
500
499
498
497
1.40
NDRV SWITCHING FREQUENCY (kHz)
-40
fSW = 1.25MHz
1.35
1.30
1.25
1.20
1.15
496
48.4
495
48.0
-15
10
35
60
85
1.10
-50
110
TEMPERATURE (°C)
-25
0
25
50
75
TEMPERATURE (°C)
125
100
DEAD TIME vs. TEMPERATURE
65
VIN = 24V
RDT = 24.9kΩ
RRT = 100kΩ
-15
10
35
60
85
110
DEAD TIME vs. RDT
200
MAX5069 toc26
70
-40
TEMPERATURE (°C)
MAX5069 toc25
180
160
140
60
TIME (ns)
-40
TIME (ns)
NDRV SWITCHING FREQUENCY (kHz)
1
MAX5069 toc24
11.5
62.6
RON (Ω)
62.7
2
fSW (MHz)
62.8
12.5
MAX5069 toc20
62.9
FLTINT CURRENT (µA)
13.0
MAX5069 toc19
63.0
NDRVA SWITCHING FREQUENCY (fSW)
vs. RRT
HYST RON vs. TEMPERATURE
MAX5069 toc21
FLTINT CURRENT vs. TEMPERATURE
55
50
120
100
80
60
40
45
20
40
0
-40
-15
10
35
60
TEMPERATURE (°C)
85
110
1
10
100
RDT (kΩ)
_______________________________________________________________________________________
7
MAX5069
Typical Operating Characteristics (continued)
(VIN = +23.6V for MAX5069A/B at startup, then reduces to +12V, VIN = +12V for the MAX5069C/D, CIN = CREG5 = 0.1µF, CVCC = 1µF,
RRT = 100kΩ, NDRV_ = floating, VFB = 0V, VCOMP = floating, VCS = 0V, TA = +25°C, unless otherwise noted.)
MAX5069
High-Frequency, Current-Mode PWM Controller
with Accurate Oscillator and Dual FET Drivers
Pin Description
PIN
MAX5069A
MAX5069D
MAX5069B
MAX5069C
NAME
FUNCTION
1
1
RT
Oscillator-Timing Resistor. Connect a resistor from RT to AGND to set the internal oscillator
frequency.
2
—
SYNC
8
External-Clock Sync Input. Connect SYNC to AGND when not using an external clock.
—
2
HYST
3
3
SCOMP
Hysteresis Input
4
4
DT
5
5
UVLO/EN
6
6
FB
7
7
COMP
Error-Amplifier Output
Fault-Integration Input. A capacitor connected to FLTINT charges with an internal 60µA
current source during persistent current-limit faults. Switching terminates when VFLTINT is
2.8V. An external resistor connected in parallel discharges the capacitor. Switching
resumes when VFLTINT drops to 1.6V.
Slope-Compensation Capacitor Connection
Dead-Time Resistor Connection. Connect a resistor from DT to AGND to program the
output dead time. Connect to REG5 for NDRVA and NDRVB maximum 50% duty cycle.
Externally Programmable Undervoltage Lockout. UVLO/EN programs the input start
voltage. Connect UVLO/EN to AGND to disable the output.
Error-Amplifier Inverting Input
8
8
FLTINT
9
9
CS
Current-Sense Resistor Connection
10
10
AGND
Analog Ground. Connect to PGND.
11
11
PGND
Power Ground. Connect to AGND through a ground plane.
12
12
NDRVB
Gate-Driver Output B. Connect NDRVB to the gate of the external N-channel FET.
13
13
NDRVA
Gate-Driver Output A. Connect NDRVA to the gate of the external N-channel FET.
14
14
VCC
9V Linear-Regulator Output. Decouple VCC with a minimum 1µF ceramic capacitor to
AGND; also internally connected to the FET drivers.
15
15
IN
Power-Supply Input. IN provides power for all internal circuitry except the gate driver.
Decouple IN with 0.1µF to AGND (see the Typical Operating Circuit).
16
16
REG5
5V Linear-Regulator Output. Decouple REG5 to AGND with 0.1µF ceramic capacitor.
EP
EP
PAD
Exposed Paddle. Connect to GND.
_______________________________________________________________________________________
High-Frequency, Current-Mode PWM Controller
with Accurate Oscillator and Dual FET Drivers
The MAX5069 is a current-mode, dual MOSFET driver,
PWM controller designed for isolated and nonisolated
push-pull or half-/full-bridge power-supply applications.
A bootstrap UVLO with a programmable hysteresis,
very low startup, and low operating current result in
high-efficiency universal-input power supplies. In addition to the internal bootstrap UVLO, the device also
offers programmable input startup and turn-off voltages, programmed through the UVLO/EN pin.
The MAX5069 includes a cycle-by-cycle current limit
that turns off the gate drive to the external MOSFET
during an overcurrent condition. The MAX5069 integrating fault protection reduces average power dissipation
during persistent fault conditions (see the Integrating
Fault Protection section).
The MAX5069 features a very accurate, wide-range,
programmable oscillator that simplifies and optimizes
the design of the magnetics. The MAX5069A/B are well
suited for universal-input (rectified 85VAC to 265VAC)
or telecom (-36VDC to -72VDC) power supplies. The
MAX5069C/D are well suited for low-input voltage
(10.8VDC to 24VDC) power supplies.
The MAX5069 high-frequency, universal input,
offline/telecom, current-mode PWM controller integrates
all the building blocks necessary for implementing ACDC and DC-DC fixed-frequency power supplies. Pushpull and half-/full-bridge 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 the programmable slope compensation stabilizes
the current loop when operating both FET drivers at a
combined 100% duty cycle.
An input UVLO programs the input-supply startup voltage and ensures proper operation during brownout conditions. An external voltage-divider programs the supply
startup voltage. The MAX5069B/C feature a programmable UVLO hysteresis. The MAX5069A/B feature an additional internal bootstrap UVLO with large hysteresis that
requires a minimum startup voltage of 23.6V. The
MAX5069A/D start up from a minimum voltage of 10.8V.
Internal digital soft-start reduces output-voltage overshoot at startup.
A single external resistor programs the switching frequency of each MOSFET driver from 25kHz to
1.25MHz. The MAX5069A/D provide a SYNC input for
synchronization to an external clock. The maximum FET
driver duty cycle for each driver is limited to 50%.
Programmable dead time allows additional flexibility in
optimizing magnetic design and overcoming parasitic
effects. Integrating fault protection ignores transient
overcurrent conditions for a set length of time. The
length of time is programmed by an external capacitor.
The internal thermal-shutdown circuit protects the
device should the junction temperature exceed
+170°C.
Power supplies designed with the MAX5069A/B use a
high-value startup resistor, R1, which charges a reservoir capacitor, C1 (Figure 1). During this initial period,
while the voltage is less than the internal bootstrap
UVLO threshold, the device typically consumes only
47µA of quiescent current. This low startup current and
the large bootstrap UVLO hysteresis help to minimize
the power dissipation across R1 even at the high end of
the universal AC input voltage (265VAC).
The MAX5069 includes a cycle-by-cycle current limit
that turns off the gates to both external MOSFETs during an overcurrent condition. When using the
MAX5069A/B in the bootstrap mode (if the power-supply output is shorted), the tertiary winding voltage
drops below the 9.74V threshold, causing the UVLO to
turn off the gate to the external power MOSFETs. This
reinitiates a startup sequence with soft-start.
Current-Mode Control
The MAX5069 offers a current-mode control operation
feature, such as leading-edge blanking with a dual
internal path that only blanks the sensed current signal
applied to the input of the PWM controller. The currentlimit comparator monitors CS at all times and provides
cycle-by-cycle current limit without being blanked. The
leading-edge blanking of the CS signal prevents the
PWM comparator from prematurely terminating the on
cycle. The CS signal contains a leading-edge spike
that results from the MOSFET’s gate charge current,
and the capacitive and diode reverse-recovery current
of the power circuit. Since this leading-edge spike is
normally lower than the current-limit comparator threshold, current limiting is provided under all conditions.
Use the MAX5069 in push-pull and half-/full-bridge applications where a large duty cycle is desired. The large
duty cycle results in much lower operating primary RMS
currents through the MOSFET switches, and in most
cases it results in a smaller inductor and output filter
capacitor. The MAX5069 adjusted slope compensation
allows for easy stabilization of the inner current loop.
_______________________________________________________________________________________
9
MAX5069
Detailed Description
MAX5069
High-Frequency, Current-Mode PWM Controller
with Accurate Oscillator and Dual FET Drivers
D3
D1
VOUT
C7
VIN
R1
C1
R6
R2
IN
D2
UVLO/EN
C2
FLTINT
RHYST
C3
HYST
VCC
C4
R9
R7
MAX5069B
REG5
R3
RT
NDRVB
Q2
NDRVA
R4
R10
Q1
DT
CS
C5
SCOMP
FB
R8
AGND PGND COMP
R5
C6
Figure 1. Nonisolated Power Supply with Programmable Input Supply Voltage
Undervoltage Lockout
The MAX5069 features an input voltage UVLO/EN function to enable the PWM controller before any operation
can begin. The MAX5069A/D shut down if the voltage
at UVLO/EN falls below its 1.18V threshold. The
MAX5069B/C also incorporate a UVLO hysteresis input
to set the desired turn-off voltage.
MAX5069A/D UVLO Adjustment
The MAX5069A/D have an input voltage UVLO/EN with
a 1.231V threshold. Before any operation can commence, the UVLO/EN voltage must exceed the 1.231V
threshold. The UVLO circuit keeps the PWM comparator, ILIM comparator, oscillator, and output drivers shutdown to reduce current consumption (see the
Functional Diagram).
10
Calculate R6 in Figure 2 by using the following formula:
⎛ V
⎞
R6 = ⎜ ON − 1⎟ × R7
V
⎝ ULR2
⎠
where VULR2 is the UVLO/EN’s 1.231V rising threshold
and VON is the desired startup voltage. Choose an R7
value in the 20kΩ range.
After a successful startup, the MAX5069A/D shut down
if the voltage at UVLO/EN drops below its 1.18V falling threshold.
MAX5069B/C UVLO with
Programmable Hysteresis
In addition to programmable undervoltage lockout during startup, the MAX5069B/C incorporate a UVLO/EN
______________________________________________________________________________________
High-Frequency, Current-Mode PWM Controller
with Accurate Oscillator and Dual FET Drivers
MAX5069
VIN
MAX5069A/D
R6
UVLO/EN
VHYST = VON - VOFF
R7
1.23V
1.18V
VOFF
Figure 2. Setting the MAX5069A/D Undervoltage Lockout
Threshold
hysteresis that allows the user to set a voltage (VOFF) to
disable the controller (see Figure 3).
At the beginning of the startup sequence, UVLO/EN is
below the 1.23V threshold, and Q1 turns on connecting
RHYST to GND (Figure 4). Once the UVLO 1.23V threshold is crossed, Q1 turns off, resulting in the series combination of R6, RHYST, and R7, placing the MAX5069 in
normal operating condition.
Calculate the turn-on voltage (V ON) by using the following formula:
⎛ V
⎞
R6 = ⎜ ON − 1⎟ × RHYST
⎝ VULR2
⎠
VON
Figure 3. MAX5069 Hysteresis
VIN
MAX5069B/C
R6
UVLO/EN
RHYST
1.23V
1.18V
HYST
Q1
R7
where VULR2 is the UVLO/EN’s 1.23V rising threshold.
Choose an RHYST value in the 20kΩ range.
The MAX5069 turns off when the MAX5069 UVLO/EN
falls below the 1.18V falling threshold. The turn-off voltage (VOFF) is then defined as:
⎛ V
⎞
R7 = R6 / ⎜ OFF − 1⎟ − RHYST
⎝ VULF2
⎠
where VULF2 is the 1.18V UVLO/EN falling threshold.
Bootstrap Undervoltage Lockout
(MAX5069A/B)
In addition to the externally programmable UVLO function offered by the MAX5069, the MAX5069A/B feature
an additional internal bootstrap UVLO for use in highvoltage power supplies (see the Functional Diagram).
This allows the device to bootstrap itself during initial
Figure 4. Setting the MAX5069B/C Turn-On/Turn-Off Voltages
power-up. The MAX5069A/B start when VIN exceeds
the bootstrap UVLO threshold of 23.6V.
During startup, the UVLO circuit keeps the PWM comparator, ILIM comparator, oscillator, and output drivers
shut down to reduce current consumption. Once V IN
reaches 23.6V, the UVLO circuit turns on both the PWM
and ILIM comparators, as well as the oscillator, and
allows the output driver to switch. If VIN drops below
9.7V, the UVLO circuit shuts down the PWM comparator, ILIM comparator, oscillator, and output drivers,
returning the MAX5069A/B to the startup mode.
______________________________________________________________________________________
11
MAX5069
High-Frequency, Current-Mode PWM Controller
with Accurate Oscillator and Dual FET Drivers
MAX5069A/B Startup Operation
Normally, VIN is derived from the tertiary winding of the
transformer. However, at startup there is no energy
delivered through the transformer; hence, a special
bootstrap sequence is required. Figure 5 shows the
voltages on VIN and VCC during startup. Initially, both
VIN and VCC are 0V. After the input voltage is applied,
C1 charges through the startup resistor, R1, to an intermediate voltage (see Figure 1). At this point, the internal regulator begins charging C3 (see Figure 5). Only
47µA of the current supplied by R1 is used by the
MAX5069A/B. The remaining input current charges C1
and C3. The charging of C3 stops when the VCC voltage reaches approximately 9.5V. The voltage across
C1 continues rising until it reaches the wake-up level of
23.6V. Once VIN exceeds the bootstrap UVLO threshold, NDRVA/NDRVB begin switching the MOSFETs and
energy is transferred to the secondary and tertiary outputs. If the voltage on the tertiary output builds to higher than 9.74V (the bootstrap UVLO lower threshold),
startup ends and sustained operation commences.
If VIN drops below 9.74V before startup is complete, the
device goes back to low-current UVLO. If this occurs,
increase the value of C1 to store enough energy to
allow for the voltage at the tertiary winding to build up.
Startup Time Considerations for
Power Supplies Using the MAX5069A/B
The VIN bypass capacitor, C1, supplies current immediately after wakeup (see Figure 1). The size of C1 and
the connection configuration of the tertiary winding
determine the number of cycles available for startup.
Large values of C1 increase the startup time and also
supply extra gate charge for more cycles during initial
startup. If the value of C1 is too small, VIN drops below
9.74V because NDRVA/NDRVB do not have enough
time to switch and build up sufficient voltage across the
tertiary output that powers the device. The device goes
back into UVLO and does not start. Use low-leakage
capacitors for C1 and C3.
Generally, offline power supplies keep typical startup
times to less than 500ms, even in low-line conditions
(85VAC input for universal offline applications or
36VDC for telecom applications). Size the startup resistor, R1, to supply both the maximum startup bias of the
device (90µA) and the charging current for C1 and C3.
The bypass capacitor, C3, must charge to 9.5V, and
C1 must charge to 24V, within the desired time period
of 500ms. Because of the internal soft-start time of the
MAX5069, C1 must store enough charge to deliver current to the device for at least 2047 oscillator clock
cycles. To calculate the approximate amount of capacitance required, use the following formula:
12
VCC
2V/div
MAX5069
VIN PIN
5V/div
0V
100ms/div
Figure 5. V IN and V CC During Startup When Using the
MAX5069 in Bootstrapped Mode (See Figure 1)
Ig = Qgtot x fSW
(IIN + Ig ) x t SS
C1 =
VHYST
where IIN is the MAX5069’s internal supply current after
startup (3.3mA, typ), Qgtot is the total gate charge for
Q1 and Q2, fSW is the MAX5069’s programmed output
switching frequency, VHYST is the bootstrap UVLO hysteresis (12V), and tss is the internal soft-start time (2047
clock cycles x 1 / fOSC).
Example:
Ig = (16nC) (250kHz) ≅ 4mA
fOSC = 500kHz
tSS = 2047 x (1 / fOSC) = 4.1ms
C1 =
(3.3mA + 4mA) (4.1ms)
= 2.5µF
12V
Use a 4.7µF ceramic capacitor for C1.
Assuming C1 > C3, calculate the value of R1 as follows:
VSUVR × C1
500ms
VIN(MIN) − 0.5 x VSUVR
IC1 ≅
R1 ≅
IC1 + ISTART
where V SUVR is the bootstrap UVLO wakeup level
(23.6V max), VIN(MIN) is the minimum input supply voltage for the application (36V for telecom), and ISTART is
the VIN supply current at startup (90µA, max).
______________________________________________________________________________________
High-Frequency, Current-Mode PWM Controller
with Accurate Oscillator and Dual FET Drivers
MAX5069
VOUT
C7
VIN
R1
C1
R6
R2
IN
C2
UVLO/EN
FLTINT
C3
VCC
RHYST
MAX5069B
HYST
R7
C4
REG5
NDRVB
R3
Q2
RT
NDRVA
Q1
R4
DT
CS
SCOMP
FB
C5
AGND
R12
R8
C8
VCC
PGND COMP
R5
C10
C6
R13
PS2913
R10
R9
R11
MAX8515
R14
Figure 6. Secondary-Side, Regulated, Isolated Power Supply
For example:
24V x 4.7µF
= 225µA
500ms
36V − 12V
R1 ≅
= 76kΩ
225µA + 90µA
IC1 =
To minimize power loss on this resistor, choose a higher value for R1 than the one calculated above (if a
longer startup time can be tolerated).
The above startup method applies to a circuit similar to
the one shown in Figure 1. In this circuit, the tertiary
winding has the same phase as the secondary windings. Thus, the voltage on the tertiary winding at any
given time is proportional to the output voltage. The
minimum discharge time of C1 from 22V to 10V must
be greater than the soft-start time (tSS).
______________________________________________________________________________________
13
MAX5069
High-Frequency, Current-Mode PWM Controller
with Accurate Oscillator and Dual FET Drivers
Oscillator/Switching Frequency
Use an external resistor at RT to program the MAX5069
internal oscillator frequency from 50kHz to 2.5MHz. The
MAX5069 NDRVA/NDRVB switching frequency is one
half of the programmed oscillator frequency with a
maximum 50% duty cycle.
Use the following formula to calculate the internal oscillator frequency:
fosc =
Dead time =
11
10
RRT
60
× RDT (ns)
29.4
where RDT is in kΩ and the dead time is in ns.
where fOSC is the oscillator frequency and RRT is a
resistor connected from RT to AGND.
Choose the appropriate resistor at RT to calculate the
desired switching frequency (fSW):
RRT =
shorting out the transformer’s primary. The MAX5069
allows the dead-time delay required to turn on the
NDRVB FET after the NDRVA FET turns off. The dead
time can be programmed to a minimum of 30ns to 1 / (0.5
x fSW). Connect a resistor between DT and AGND to set
the desired dead time. Calculate the dead time using the
following formula:
1011
2fSW
For the maximum 50% duty cycle at NDRVA/NDRVB,
connect DT to REG5.
Dual N-Channel MOSFET Switch Driver
The MAX5069 drives two external N-channel MOSFETs
in push-pull isolated power supplies. Each MOSFET
driver operates with a maximum 50% duty cycle. The
NDRV_ outputs are supplied by the internal regulator
(VCC), which is internally set to approximately 9.5V. For
the universal input voltage range, the MOSFETs used
must be able to withstand at least twice the DC level of
the high-line input voltage. Both NDRVA and NDRVB
can source and sink in excess of 650mA and 1000mA
peak current, respectively.
Dead-Time Control
In typical push-pull designs, it is desirable to add some
extra delay between the turning off of one MOSFET and
the turning on of the next MOSFET (Figure 7). The extra
time ensures that the first MOSFET is fully off when the
other MOSFET starts to turn on. This prevents both
MOSFETs from being on simultaneously, thus avoiding
External Synchronization (MAX5069A/D)
The MAX5069A/D can be synchronized using an external clock at the SYNC input. For proper frequency synchronization, the SYNC’s input frequency must be at
least 25% higher than the MAX5069A/D programmed
internal oscillator frequency. Connect SYNC to AGND
when not using an external clock.
Integrating Fault Protection
The integrating fault-protection feature allows transient
overcurrent conditions to be ignored for a programmable amount of time, giving the power supply time to
behave like a current source to the load. For example,
this can occur under load-current transients when the
control loop requests maximum current to keep the output voltage from going out of regulation. Program the
fault-integration time by connecting an external suitably
sized capacitor to the FLTINT. Under sustained overcurrent faults, the voltage across this capacitor ramps
up towards the FLTINT shutdown threshold (typically
2.8V). Once the threshold is reached, the power supply
shuts down. A high-value bleed resistor connected in
parallel with the FLTINT capacitor allows it to discharge
towards the restart threshold (typically 1.6V). Once this
threshold is reached, the supply restarts with a new
soft-start cycle.
SYNC
MAX5069A/D
tDT
DEAD TIME
NDRVA
NDRVB
RT
工商网监
湘ICP备2023018690号
