19-3289; Rev 1; 6/05
IT
TION K
VALUA
E
BLE
AVAILA
3V to 28V Input, Low-Cost, Hysteretic
Synchronous Step-Down Controllers
General Description
Features
♦
3V to 28V Supply Voltage Range
♦
1.2% Accurate Over Temperature
♦
Adjustable Output Voltage Down to 0.6V
♦
200kHz to 500kHz Switching Frequency
♦
Adjustable Temperature-Compensated Hiccup
Current Limit
♦
Lossless Peak Current Sensing
♦
Monotonic Startup into Prebias Output
(MAX8576/MAX8578)
♦
Startup Overvoltage Protection
(MAX8577/MAX8579)
♦
Enable/Shutdown
♦
Adjustable Soft-Start
MAX8576–MAX8579
The MAX8576–MAX8579 synchronous PWM buck con-
trollers use a hysteretic voltage-mode control algorithm
to achieve a fast transient response without requiring
loop compensation. The MAX8576/MAX8577 contain an
internal LDO regulator allowing the controllers to func-
tion from only one 3V to 28V input supply. The
MAX8578/MAX8579 do not contain the internal LDO
and require a separate supply to power the IC when the
input supply is higher than 5.5V. The MAX8576–
MAX8579 output voltages are adjustable from 0.6V to
0.9 x V
IN
at loads up to 15A.
Nominal switching frequency is programmable over the
200kHz to 500kHz range. High-side MOSFET sensing is
used for adjustable hiccup current-limit and short-cir-
cuit protection. The MAX8576/MAX8578 can start up
into a precharged output without pulling the output volt-
age down. The MAX8577/MAX8579 have startup output
overvoltage protection (OVP), and will pull down a
precharged output.
Applications
Motherboard Power Supplies
AGP and PCI-Express Power Supplies
Graphic-Card Power Supplies
Set-Top Boxes
Point-of-Load Power Supplies
Ordering Information
PART
MAX8576EUB
MAX8577EUB
MAX8578EUB
MAX8579EUB
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
10 µMAX
®
10 µMAX
10 µMAX
10 µMAX
Typical Operating Circuit
INPUT
UP TO 28V
FB
OCSET
SS
IN
VL
MAX8576
MAX8577
DH
OUTPUT
0.6V TO 0.9 x
V
IN
LX
GND
DL
BST
µMAX is a registered trademark of Maxim Integrated Products, Inc.
Pin Configurations appear 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.
3V to 28V Input, Low-Cost, Hysteretic
Synchronous Step-Down Controllers
MAX8576–MAX8579
ABSOLUTE MAXIMUM RATINGS
IN to GND (MAX8576/MAX8577) ...........................-0.3V to +30V
VL to GND (MAX8576/MAX8577).............................-0.3V to +6V
IN to VL (MAX8576/MAX8577) ...............................-0.3V to +30V
V
CC
to GND (MAX8578/MAX8579) ..........................-0.3V to +6V
SS to GND (MAX8576/MAX8577) ...............-0.3V to (V
VL
+ 0.3)V
SS to GND (MAX8578/MAX8579)...............-0.3V to (V
CC
+ 0.3)V
DL to GND (MAX8576/MAX8577) ...............-0.3V to (V
VL
+ 0.3)V
DL to GND (MAX8578/MAX8579) ..............-0.3V to (V
CC
+ 0.3)V
BST to GND ............................................................-0.3V to +36V
BST to LX..................................................................-0.3V to +6V
LX to GND .....................-1V (-2.5V for <50ns Transient) to +30V
DH to LX..................................................-0.3V to +(V
BST
+ 0.3)V
FB to GND ................................................................-0.3V to +6V
EN to GND (MAX8578/MAX8679EUB) .....................-0.3V to +6V
OCSET to GND (MAX8576/MAX8677) ........-0.3V to (V
IN
+ 0.3)V
OCSET to GND (MAX8578/MAX8679) ...................-0.3V to +30V
OCSET to LX (MAX8576/MAX8677) ............-0.6V to (V
IN
+ 0.3)V
OCSET to LX (MAX8578/MAX8679) .......................-0.6V to +30V
DH and DL Continuous Current ............................±250mA RMS
Continuous Power Dissipation (T
A
= +70°C)
10-Pin µMAX (derate 5.6mW/°C above +70°C) ...........444mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°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 (MAX8576/MAX8577 only), 4.7µF capacitor from VL (MAX8576/MAX8577 only) or V
CC
(MAX8578/MAX8579 only) to GND;
V
CC
= V
EN
= 5V (MAX8578/MAX8579 only); 0.01µF capacitor from SS to GND; V
FB
= 0.65V; V
BST
= 5V; V
LX
= V
GND
= 0V; V
OCSET
=
11.5V; DH = unconnected; DL = unconnected;
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
SUPPLY VOLTAGES
IN Supply Voltage
V
CC
Input Voltage
VL Output Voltage
VL Maximum Output Current
VL or V
CC
Undervoltage Lockout
(UVLO)
MAX8576/MAX8577
IN = VL (MAX8576/MAX8577)
MAX8576/MAX8577
I
VL
= 10mA (MAX8576/MAX8577)
MAX8576/MAX8577
Rising
Falling
Hysteresis
No switching, V
FB
= 0.65V
(MAX8576/MAX8577)
Supply Current
V
EN
= 0V or V
FB
= 0.65V, no
switching (MAX8578/MAX8579)
REGULATOR
Output Regulation Accuracy
Output Regulation Hysteresis
FB Propagation Delay
Overvoltage-Protection (OVP)
Threshold
High-Side Current-Sense
Program Current (Note 2)
T
A
= +85°C
T
A
= +25°C
42.5
V
FB
peak
(Note 1)
FB falling to DL falling
FB rising to DH falling
0.70
0.593
12.5
0.6
20
50
70
0.75
60
50
57.5
0.80
0.607
28.0
V
mV
ns
V
µA
V
IN
= 12V
V
IN
= V
VL
= 5V
V
IN
= V
VL
= 3.3V
V
CC
= 5V
V
CC
= 3.3V
5.5
3.0
3.0
4.75
20
2.75
2.4
2.8
2.45
350
0.6
1.1
0.6
0.6
0.6
2
3
2
2
2
mA
2.90
2.5
5.0
28.0
5.5
5.5
5.25
V
V
V
mA
V
mV
CONDITIONS
MIN
TYP
MAX
UNITS
2
_______________________________________________________________________________________
3V to 28V Input, Low-Cost, Hysteretic
Synchronous Step-Down Controllers
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= 12V (MAX8576/MAX8577 only), 4.7µF capacitor from VL (MAX8576/MAX8577 only) or V
CC
(MAX8578/MAX8579 only) to GND;
V
CC
= V
EN
= 5V (MAX8578/MAX8579 only); 0.01µF capacitor from SS to GND; V
FB
= 0.65V; V
BST
= 5V; V
LX
= V
GND
= 0V; V
OCSET
=
11.5V; DH = unconnected; DL = unconnected;
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
High-Side Current-Sense
Overcurrent Trip Adjustment
Range
Soft-Start Internal Resistance
Fault Hiccup Internal SS Pulldown
V
LX
< V
OCSET
and V
FB
< V
SS
Current
DRIVER SPECIFICATIONS
DH Driver Resistance
DL Driver Resistance
Dead Time
DH Minimum On-Time
DL Minimum On-Time
BST Current
EN
Input Voltage Low
Input Voltage High
THERMAL SHUTDOWN
Thermal Shutdown
Rising temperature, hysteresis = 20°C (typ)
+160
°C
V
CC
= 3V (MAX8578/MAX8579)
V
CC
= 5.5V (MAX8578/MAX8579)
1.5
0.7
V
V
Normal operation
Current fault
V
BST
- V
LX
= 5.5V, V
LX
= 28V, V
FB
< V
SS
Sourcing current
Sinking current
Sourcing current
Sinking current
DH low to DL high and DL low to DH high
(adaptive)
2.6
1.9
2.6
1.1
40
140
120
580
1.65
245
220
4.0
3.0
4.0
2.0
Ω
Ω
ns
ns
ns
mA
V
IN
- V
OCSET
CONDITIONS
MIN
0.05
45
80
250
TYP
MAX
0.40
125
UNITS
V
kΩ
nA
MAX8576–MAX8579
ELECTRICAL CHARACTERISTICS
(V
IN
= 12V (MAX8576/MAX8577 only), 4.7µF capacitor from VL (MAX8576/MAX8577 only) or V
CC
(MAX8578/MAX8579 only) to GND;
V
CC
= V
EN
= 5V (MAX8578/MAX8579 only); 0.01µF capacitor from SS to GND; V
FB
= 0.65V; V
BST
= 5V; V
LX
= V
GND
= 0V; V
OCSET
=
11.5V; DH = unconnected; DL = unconnected;
T
A
= -40°C to +85°C,
unless otherwise noted. Note 3)
PARAMETER
SUPPLY VOLTAGES
IN Supply Voltage
V
CC
Input Voltage
VL Output Voltage
VL Maximum Output Current
MAX8576/MAX8577
IN = VL, MAX8576/MAX8577
MAX8576/MAX8577
I
VL
= 10mA, MAX8576/MAX8577
MAX8576/MAX8577
5.5
3.0
3.0
4.75
20
28.0
5.5
5.5
5.25
V
V
V
mA
CONDITIONS
MIN
TYP
MAX
UNITS
_______________________________________________________________________________________
3
3V to 28V Input, Low-Cost, Hysteretic
Synchronous Step-Down Controllers
MAX8576–MAX8579
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= 12V (MAX8576/MAX8577 only), 4.7µF capacitor from VL (MAX8576/MAX8577 only) or V
CC
(MAX8578/MAX8579 only) to GND;
V
CC
= V
EN
= 5V (MAX8578/MAX8579 only); 0.01µF capacitor from SS to GND; V
FB
= 0.65V; V
BST
= 5V; V
LX
= V
GND
= 0V; V
OCSET
=
11.5V; DH = unconnected; DL = unconnected;
T
A
= -40°C to +85°C,
unless otherwise noted. Note 3)
PARAMETER
VL or V
CC
Undervoltage Lockout
(UVLO)
Rising
Falling
No switching, V
FB
= 0.65V
(MAX8576/MAX8577)
Supply Current
V
EN
= 0V or V
FB
= 0.65V, no
switching (MAX8578/MAX8579)
REGULATOR
Output Regulation Accuracy
Overvoltage-Protection (OVP)
Threshold
High-Side Current-Sense Over-
Current Trip Adjustment Range
DRIVER SPECIFICATIONS
DH Driver Resistance
DL Driver Resistance
DH Minimum On-Time
DL Minimum On-Time
EN
Input Voltage Low
Input Voltage High
V
CC
= 3V, MAX8578/MAX8579
V
CC
= 5.5V, MAX8578/MAX8579
1.5
0.7
V
V
Normal operation
Sourcing current
Sinking current
Sourcing current
Sinking current
4
3.0
4.0
2.0
245
220
Ω
Ω
ns
ns
V
IN
- V
OCSET
V
FB
peak
0.591
0.70
0.05
0.607
0.80
0.40
V
V
V
V
IN
= 12V
V
IN
= V
VL
= 5V
V
IN
= V
VL
= 3.3V
V
CC
= 5V
V
CC
= 3.3V
CONDITIONS
MIN
2.75
2.40
TYP
MAX
2.90
2.55
2
3.5
2
2
2
mA
UNITS
V
Note 1:
Guaranteed by design.
Note 2:
This current linearly compensates for the MOSFET temperature coefficient.
Note 3:
Specifications to -40°C
are guaranteed by design and not production tested.
4
_______________________________________________________________________________________
3V to 28V Input, Low-Cost, Hysteretic
Synchronous Step-Down Controllers
MAX8576–MAX8579
Typical Operating Characteristics
(T
A
= +25°C, unless otherwise noted.)
EFFICIENCY vs. LOAD CURRENT
(CIRCUIT OF FIGURE 2)
MAX8576-79 toc01
EFFICIENCY vs. LOAD CURRENT
(CIRCUIT OF FIGURE 3)
MAX8576-79 toc02
LOAD REGULATION
(CIRCUIT OF FIGURE 2)
1.83
1.82
OUTPUT VOLTAGE (V)
1.81
1.80
1.79
1.78
1.77
MAX8576-79 toc03
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0.1
1
10
LOAD CURRENT (A)
V
OUT
= 1.5V
V
OUT
= 3.3V
V
OUT
= 2.5V
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
V
OUT
= 1.5V
V
OUT
= 2.5V
V
OUT
= 3.3V
V
OUT
= 1.8V
1.84
V
OUT
= 1.8V
V
IN
= 12V
100
V
IN
= 12V
0.1
1
LOAD CURRENT (A)
10
1.76
1.75
0
5
10
15
LOAD CURRENT (A)
0
LINE REGULATION
(CIRCUIT OF FIGURE 2)
MAX8576-79 toc04
LINE REGULATION
(CIRCUIT OF FIGURE 3)
MAX8576-79 toc05
SWITCHING FREQUENCY vs. INPUT
VOLTAGE (CIRCUIT OF FIGURE 3)
550
SWITCHING FREQUENCY (kHz)
500
450
400
350
300
250
200
MAX8576-79 toc06
1.85
1.84
OUTPUT VOLTAGE (V)
1.83
1.82
1.81
15A LOAD
1.80
1.79
5
10
15
INPUT VOLTAGE (V)
20
0A LOAD
1.86
1.84
OUTPUT VOLTAGE (V)
1.82
1.80
1.78
1.76
1.74
1.72
1.70
5A LOAD
NO LOAD
600
25
5
10
15
INPUT VOLTAGE (V)
20
25
5
10
15
INPUT VOLTAGE (V)
20
25
LOAD TRANSIENT
(CIRCUIT OF FIGURE 2)
MAX8576-79 toc07
LOAD TRANSIENT
(CIRCUIT OF FIGURE 3)
MAX8576-79 toc08
5A
I
OUT
I
OUT
12A
6A
2.5A
V
OUT
50mV/div
AC-COUPLED
V
OUT
50mV/div
AC-COUPLED
40μs/div
40μs/div
_______________________________________________________________________________________
5
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