19-3656; Rev 1; 2/07
1A, 40V, MAXPower Step-Down
DC-DC Converters
General Description
The MAX5080/MAX5081 are 250kHz PWM step-down
DC-DC converters with an on-chip, 0.3Ω high-side
switch. The input voltage range is 4.5V to 40V for the
MAX5080 and 7.5V to 40V for the MAX5081. The output
is adjustable from 1.23V to 32V and can deliver up to
1A of load current.
Both devices utilize a voltage-mode control scheme for
good noise immunity in the high-voltage switching envi-
ronment and offer external compensation allowing for
maximum flexibility with a wide selection of inductor val-
ues and capacitor types. The switching frequency is
internally fixed at 250kHz and can be synchronized to
an external clock signal through the SYNC input. Light
load efficiency is improved by automatically switching
to a pulse-skip mode.
All devices include programmable undervoltage lock-
out and soft-start. Protection features include cycle-by-
cycle current limit, hiccup-mode output short-circuit
protection, and thermal shutdown. Both devices are
available in a space-saving, high-power (2.7W), 16-pin
TQFN package and are rated for operation over the
-40°C to +125°C temperature range.
Features
♦
4.5V to 40V (MAX5080) or 7.5V to 40V (MAX5081)
Input Voltage Range
♦
1A Output Current
♦
V
OUT
Range From 1.23V to 32V
♦
Internal High-Side Switch
♦
Fixed 250kHz Internal Oscillator
♦
Automatic Switchover to Pulse-Skip Mode at
Light Loads
♦
External Frequency Synchronization
♦
Thermal Shutdown and Short-Circuit Protection
♦
Operates Over the -40°C to +125°C Temperature
Range
♦
Space-Saving (5mm x 5mm) High-Power 16-Pin
TQFN Package
MAX5080/MAX5081
Ordering Information
PART
MAX5080ATE
MAX5081ATE
TEMP RANGE
-40°C to +125°C
-40°C to +125°C
PIN-
PACKAGE
16 TQFN-EP*
16 TQFN-EP*
PKG
CODE
T1655-2
T1655-2
Applications
FireWire
®
Power Supplies
Distributed Power
Automotive
Industrial
*EP
= Exposed pad.
Pin Configurations appear at end of data sheet.
FireWire is a registered trademark of Apple Computer, Inc.
Typical Operating Circuits
V
IN
4.5V TO 40V
C
F
D1
IN
R1
DVREG
C-
C+
BST
LX
C
BST
L1
V
OUT
C6
C1
REG
MAX5080
ON/OFF
SYNC SGND PGND
C2
PGND
SS
C
SS
FB
D2
C5
R6
R3
C8
R2
COMP
R5
C7
R4
PGND
Typical Operating Circuits continued at end of data sheet.
________________________________________________________________
Maxim Integrated Products
1
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.
1A, 40V, MAXPower Step-Down
DC-DC Converters
MAX5080/MAX5081
ABSOLUTE MAXIMUM RATINGS
IN, ON/OFF
to SGND..............................................-0.3V to +45V
LX to SGND .................................................-0.3V to (V
IN
+ 0.3V)
BST to SGND ................................................-0.3V to (V
IN
+ 12V)
BST to LX................................................................-0.3V to +12V
PGND to SGND .....................................................-0.3V to +0.3V
REG, DVREG, SYNC to SGND ...............................-0.3V to +12V
FB, COMP, SS to SGND ...........................-0.3V to (V
REG
+ 0.3V)
C+ to PGND (MAX5080 only)................(V
DVREG
- 0.3V) to +12V
C- to PGND (MAX5080 only) ................-0.3V to (V
DVREG
+ 0.3V)
Continuous current through internal power MOSFET (pins 11/12
connected together and pins 13/14 connected together)
T
J
= +125°C.........................................................................3A
T
J
= +150°C.........................................................................2A
Continuous Power Dissipation
*
(T
A
= +70°C)
16-Pin TQFN (derate 33.3mW/°C above +70°C) ...2666.7mW
16-Pin TQFN (θ
JA
)........................................................30°C/W
16-Pin TQFN (θ
JC
).......................................................1.7°C/W
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
*As
per JEDEC 51 Standard
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
= V
ON/OFF
= 12V, V
REG
= V
DVREG
, V
SYNC
= PGND = SGND, T
A
= T
J
= -40°C to +125°C, unless otherwise noted. Typical values
are at T
A
= + 25°C.) (Note 1)
PARAMETER
Input Voltage Range
Undervoltage Lockout Threshold
Undervoltage Lockout Hysteresis
Switching Supply Current (PWM
Operation)
Efficiency
No-Load Supply Current
(PFM Operation)
Shutdown Current
ON/OFF CONTROL
Input Voltage Threshold
Input Voltage Hysteresis
Input Bias Current
ERROR AMPLIFIER/SOFT-START
Soft-Start Current
Reference Voltage (Soft-Start)
FB Regulation Voltage
FB Input Range
FB Input Current
COMP Voltage Range
Open-Loop Gain
Unity-Gain Bandwidth
I
COMP
= -500µA to +500µA
I
SS
V
SS
V
FB
I
COMP
= -500µA to +500µA
8
1.215
1.215
0
-250
0.25
80
1.8
15
1.228
1.228
24
1.240
1.240
1.5
+250
4.50
µA
V
V
V
nA
V
dB
MHz
V
ON/OFF
= 0 to 40V
-250
V
ON/
OFF
V
ON/
OFF
rising
1.20
1.23
0.12
+250
1.25
V
V
nA
I
SHDN
SYMBOL
V
IN
UVLO
UVLO
HYST
I
SW
MAX5080
MAX5081
V
IN
rising, MAX5080
V
IN
rising, MAX5081
MAX5080
MAX5081
V
FB
= 0V, MAX5080
V
FB
= 0V, MAX5081
V
IN
= 12V, V
OUT
= 3.3V, I
OUT
= 1A
V
IN
= 4.5V, V
OUT
= 3.3V, I
OUT
= 1A
(MAX5080)
MAX5080
MAX5081
V
ON/OFF
= 0V, V
IN
= 40V
CONDITIONS
MIN
4.5
7.5
3.9
6.8
0.4
0.7
10.5
9.5
84
88
1.4
1.3
200
2.5
2.3
300
%
TYP
MAX
40
40
4.2
7.3
UNITS
V
V
V
mA
mA
µA
2
_______________________________________________________________________________________
1A, 40V, MAXPower Step-Down
DC-DC Converters
MAX5080/MAX5081
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= V
ON/OFF
= 12V, V
REG
= V
DVREG
, V
SYNC
= PGND = SGND, T
A
= T
J
= -40°C to +125°C, unless otherwise noted. Typical values
are at T
A
= + 25°C.) (Note 1)
PARAMETER
FB Offset Voltage
OSCILLATOR
Frequency
Maximum Duty Cycle
SYNC High-Level Voltage
SYNC Low-Level Voltage
SYNC Frequency Range
PWM Modulator Gain
Ramp Level Shift (Valley)
POWER SWITCH
Switch On-Resistance
Switch Gate Charge
Switch Leakage Current
BST Leakage Current
CHARGE PUMP
C- Output Voltage Low
C- Output Voltage High
DVREG to C+ On-Resistance
LX to PGND On-Resistance
CURRENT-LIMIT COMPARATOR
Pulse-Skip Threshold
Cycle-by-Cycle Current Limit
Number of Consecutive ILIM
Events to Hiccup
Hiccup Timeout
INTERNAL VOLTAGE REGULATOR
Output Voltage
Line Regulation
Load Regulation
Dropout Voltage
V
REG
MAX5080
MAX5081
V
IN
= 5.5V to 40V, MAX5080
V
IN
= 9.0V to 40V, MAX5081
I
REG
= 0 to 20mA
V
IN
= 4.5V, I
REG
= 20mA, MAX5080
V
IN
= 7.5V, I
REG
= 20mA, MAX5081
4.75
7.6
5
8
5.25
8.4
1
1
0.25
0.5
0.5
V
mV/V
V
V
I
PFM
I
ILIM
100
1.4
200
2
7
512
Clock
periods
300
2.6
mA
A
MAX5080 only, sinking 10mA
MAX5080 only, relative to DVREG, sourcing
10mA
MAX5080 only, sourcing 10mA
Sinking 10mA
0.1
0.1
10
12
V
V
Ω
Ω
V
BST
- V
LX
= 6V
V
BST
- V
LX
= 6V
V
IN
= 40V, V
LX
= V
BST
= 0V
V
BST
= V
LX
= V
IN
= 40V
0.3
6
10
10
0.6
Ω
nC
µA
µA
f
SYNC
f
SYNC
= 150kHz to 350kHz
150
10
0.3
f
SW
D
MAX
V
SYNC
= 0V
V
SYNC
= 0V, V
IN
= 4.5V, MAX5080
V
SYNC
= 0V, V
IN
= 7.5V, MAX5081
V
SYNC
= 0V, V
IN
≤
40V
225
87
87
87
2.2
0.8
350
V
V
kHz
V/V
V
%
250
275
kHz
SYMBOL
CONDITIONS
I
COMP
= -500µA to +500µA
MIN
-5
TYP
MAX
+5
UNITS
mV
_______________________________________________________________________________________
3
1A, 40V, MAXPower Step-Down
DC-DC Converters
MAX5080/MAX5081
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= V
ON/OFF
= 12V, V
REG
= V
DVREG
, V
SYNC
= PGND = SGND, T
A
= T
J
= -40°C to +125°C, unless otherwise noted. Typical values
are at T
A
= + 25°C.) (Note 1)
PARAMETER
THERMAL SHUTDOWN
Thermal Shutdown Temperature
Thermal Shutdown Hysteresis
Temperature rising
+160
20
°C
°C
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Note 1:
100% production tested at T
A
= +25°C and T
A
= T
J
= +125°C. Limits at -40°C are guaranteed by design.
Typical Operating Characteristics
(V
IN
= 12V, see Figure 5 (MAX5080) and Figure 6 (MAX5081), T
A
= +25°C, unless otherwise noted.)
UNDERVOLTAGE LOCKOUT HYSTERESIS
vs. TEMPERATURE (MAX5080)
MAX5080 toc01
UNDERVOLTAGE LOCKOUT HYSTERESIS
vs. TEMPERATURE (MAX5081)
UNDERVOLTAGE LOCKOUT HYSTERESIS (V)
ON/OFF THRESHOLD HYSTERESIS (V)
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0
-40
-15
10
35
60
85
110
135
-40
MAX5080 toc02
ON/OFF THRESHOLD HYSTERESIS
vs. TEMPERATURE
MAX5080 toc03
1.0
UNDERVOLTAGE LOCKOUT HYSTERESIS (V)
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
-40
-15
10
35
60
85
110
1.0
0.20
0.15
0.10
0.05
135
-15
10
35
60
85
110
135
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C )
SHUTDOWN SUPPLY CURRENT
vs. INPUT VOLTAGE (MAX5080)
MAX5080 toc04
SHUTDOWN SUPPLY CURRENT
vs. INPUT VOLTAGE (MAX5081)
SHUTDOWN SUPPLY CURRENT (µA)
300
275
250
225
200
175
150
125
100
75
50
25
0
0
MAX5080 toc05
NO-LOAD SUPPLY CURRENT
vs. INPUT VOLTAGE (MAX5080)
3.5
SUPPLY CURRENT (mA)
3.0
2.5
2.0
1.5
1.0
T
A
= +25°C
T
A
= -40°C
T
A
= +85°C
T
A
= +135°C
MAX5080 toc06
250
SHUTDOWN SUPPLY CURRENT (µA)
225
200
175
150
125
100
75
50
25
0
0
5
10
15
20
25
30
35
V
ON/OFF
= 0V
T
A
= +25°C
T
A
= -40°C
T
A
= +135°C
T
A
= +85°C
4.0
T
A
= +135°C
T
A
= +85°C
T
A
= +25°C
T
A
= -40°C
V
ON/OFF
= 0V
5
10
15
20
25
30
35
40
0.5
0
0
5
10
15
20
25
30
35
40
40
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
4
_______________________________________________________________________________________
1A, 40V, MAXPower Step-Down
DC-DC Converters
Typical Operating Characteristics (continued)
(V
IN
= 12V, see Figure 5 (MAX5080) and Figure 6 (MAX5081), T
A
= +25°C, unless otherwise noted.)
MAX5080/MAX5081
OPERATING FREQUENCY
vs. TEMPERATURE
MAX5080 toc07
MAXIMUM DUTY CYCLE
vs. INPUT VOLTAGE (MAX5080)
MAX5080 toc08
MAXIMUM DUTY CYCLE
vs. INPUT VOLTAGE (MAX5081)
98
MAXIMUM DUTY CYCLE (%)
96
94
92
90
88
86
84
82
80
MAX5080 toc09
260
258
OPERATING FREQUENCY (kHz)
256
254
252
250
248
246
244
242
240
-40
-15
10
35
60
85
110
V
IN
= 40V
V
IN
= 4.5V
100
98
MAXIMUM DUTY CYCLE (%)
96
94
92
90
88
86
84
82
80
100
135
0
5
10
15
20
25
30
35
40
0
5
10
15
20
25
30
35
40
TEMPERATURE (°C)
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
OPEN-LOOP GAIN/PHASE vs. FREQUENCY
MAX5080 toc10
OUTPUT CURRENT LIMIT
vs. INPUT VOLTAGE
175
150
PHASE (DEGREES)
125
OUTPUT CURRENT LIMIT (A)
2.4
2.3
2.2
2.1
2.0
1.9
1.8
1.7
1.6
T
A
= +85°C
T
A
= +135°C
MAX5080
T
A
= -40°C
T
A
= +25°C
MAX5080 toc11
2.5
100
80
GAIN
GAIN (dB)
60
40
100
20
PHASE
0
-20
0
0.001 0.01 0.1
1
10
FREQUENCY (kHz)
75
50
100 1000 10,000
1.5
0
5
10
15
20
25
30
35
40
INPUT VOLTAGE (V)
TURN-ON/OFF WAVEFORM
MAX5080 toc12
TURN-ON/OFF WAVEFORM
MAX5080 toc13
I
LOAD
= 1A
V
ON/OFF
2V/div
I
LOAD
= 100mA
V
ON/OFF
2V/div
V
OUT
2V/div
V
OUT
2V/div
2ms/div
2ms/div
_______________________________________________________________________________________
5
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