MAXIM MAX8543, MAX858544 User Manual
General Description
The MAX8543/MAX8544 current-mode, constant-frequency PWM buck controllers operate from a 3V to
13.2V input supply and generate adjustable 0.8V to 0.9
x VINoutput voltages at loads up to 25A. They feature
adjustable switching frequency and synchronization for
noise-sensitive applications.
The MAX8543/MAX8544 can start with (or without) a preexisting bias on the output, without discharging the output. This feature simplifies tracking supply designs for
core and I/O applications and redundant supply designs.
The MAX8543/MAX8544 use the DC resistance of the
output inductor as the current-sense element for lossless, low-cost current sensing. The current-sense
threshold can be set to four discrete levels to accommodate inductors with different DC resistance values.
The MAX8544 features a power-OK monitor and two
MAX8544 controllers that can operate at 180° out-ofphase for dual-output applications.
Applications
Base Stations
Networks and Telecom
Storage
Servers
Features
♦ Prebias Startup/Monotonic
♦ 1% Output Accuracy
♦ Ceramic, Polymer, or Electrolytic Capacitors
♦ 200kHz to 1MHz Adjustable Frequency
♦ 160kHz to 1.2MHz Synchronization
♦ Lossless, Foldback Current Limit
♦ Overvoltage Protection
♦ Enable (On/Off)
♦ Adjustable Soft-Start
♦ MAX8544
Latch-Off/Autorecovery
Power-OK Monitor
Out-of-Phase Clock Output
MAX8543/MAX8544
Step-Down Controllers with Prebias Startup,
Lossless Sensing, Synchronization, and OVP
________________________________________________________________ Maxim Integrated Products 1
Ordering Information
MAX8543
ON
OPTIONAL
SYNCHRONIZATION
OFF
BST
VL
V
IN
= 3V
TO 5.5V
COMP
ILIM
FSYNC
EN
SS
PGND
GND
IN
DH
LX
DL
CS+
CS-
FB
INPUT 3V TO 13.2V
OUTPUT
0.8V TO 0.9 x V
IN
UP TO 25A
POK (MAX8544)
Typical Operating Circuit
19-3155; Rev 0; 5/04
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.
PART TEMP RANGE
PIN-PACKAGE
MAX8543EEE -40°C to +85°C 16 QSOP
MAX8544EEP -40°C to +85°C 20 QSOP
Pin Configurations appear at end of data sheet.
MAX8543/MAX8544
Step-Down Controllers with Prebias Startup,
Lossless Sensing, Synchronization, and OVP
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(VIN= 13.2V, V
BST
- VLX= 5V, TA= 0°C to +85°C, unless otherwise noted. Typical values are at TA= +25°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.
IN, EN, CS+, CS- to GND .......................................-0.3V to +14V
BST, DH to LX ..........................................................-0.3V to +6V
BST to GND ............................................................-0.3V to +20V
DL, COMP, ILIM2, SS, SYNCO,
FSYNC to GND .......................................-0.3V to (V
VL
+ 0.3V)
VL, FB, POK, ILIM1, ILIM, MODE to GND ................-0.3V to +6V
PGND to GND .......................................................-0.3V to +0.3V
Continuous Power Dissipation (T
A
= +70°C)
16-Pin QSOP (derate 8.3mW/°C above +70°C) .......666.7mW
20-Pin QSOP (derate 9.1mW/°C above +70°C) .......727.3mW
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
PARAMETER CONDITIONS
UNITS
Operating Input Voltage Range VL connected to IN for V
IN
< 5.5V 3.0
V
Quiescent Supply Current V
FB
= 0.9V, no switching 2 3 mA
10
Shutdown Supply Current
EN = GND, VL = IN, MODE = GND 20
µA
VL Undervoltage-Lockout Trip Level V
VL
rising, typical hysteresis is 80mV
2.7
V
Output Voltage Adjust Range (V
OUT
) (Note 1) 0.8 V
VL Output Voltage 5.5V < V
IN
< 13.2V, 1mA < IVL < 75mA 4.5 5 5.5 V
VL Output Current 75 mA
VOLTAGE REFERENCE
SS Shutdown Resistance From SS to GND, V
EN
= 0V 20
Ω
SS Soft-Start Current V
REF
= 0.625V 14 24 34 µA
Soft-Start Ramp Time Output from 0% to 100%, C
REF
= 0.01µF to 1µF 33
ms/µF
ERROR AMPLIFIER
FB Regulation Voltage
0.8
V
Transconductance 70
µS
COMP Shutdown Resistance From COMP to GND, V
EN
= 0V 20
Ω
FB Input Leakage Current V
FB
= 0.9V 5
nA
FB Input Common-Mode Range
V
CURRENT-SENSE AMPLIFIER
V
ILIM1
= 0V 8.8 11
4.8 6 7.2
3.2 4 4.8
Voltage Gain V
OUT
= 0 to 13V
V
ILIM1
= V
VL
2.4 3 3.6
V / V
CURRENT LIMIT
ILIM2 Output Current (MAX8544 Only) R
ILIM2
= 50kΩ to 200kΩ 4.5 5 5.5 µA
ILIM1 Input Current V
ILIM1
= 0V or V
VL
-1 +1 µA
MIN TYP MAX
13.2
EN = GND, MODE = GND, IN not connected to VL
2.52
0.792
-0.1
110 160
V
V
ILIM1
ILIM1
= (1/3)V
= (2/3)V
VL
VL
2.88
100
0.808
100
100
+0.9
13.2
MAX8543/MAX8544
Step-Down Controllers with Prebias Startup,
Lossless Sensing, Synchronization, and OVP
_______________________________________________________________________________________ 3
ELECTRICAL CHARACTERISTICS (continued)
(VIN= 13.2V, V
BST
- VLX= 5V, TA= 0°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.)
PARAMETER CONDITIONS
MIN
TYP
MAX
UNITS
V
CS+
- V
CS-, VILIM1
= 0V
50
V
CS+
- V
CS-, VILIM1
= (1/3)V
VL
85
V
CS+
- V
CS-
, V
ILIM1
= (2/3)V
VL
V
CS+
- V
CS-
, V
ILIM1
= V
VL
V
LX
- V
PGND
, R
ILIM2
= 50kΩ (MAX8544 only)
-50
V
LX
- V
PGND
, R
ILIM2
= 200kΩ (MAX8544 only)
V
LX
- V
PGND
, VFB = 0.8V (MAX8543 only)
Current-Limit Threshold
V
LX
- V
PGND
, VFB = 0V (MAX8543 only) -20 -30 -40
mV
Negative Current-Limit Threshold % of positive-direction current limit V
LX
- V
PGND
-25 -50 -85 %
CS+, CS- Input Current V
CS+
= V
CS-
= 0 or 5V -40
µA
CS+, CS- Input Common-Mode Range 0
V
OSCILLATOR
R
FSYNC
= 18.2kΩ
Switching Frequency
R
FSYNC
= 158kΩ
kHz
Minimum Off-Time Measured at DH
ns
Minimum On-Time Measured at DH 90
ns
FSYNC Synchronization Range
kHz
FSYNC Input High Pulse Width
ns
FSYNC Input Low Pulse Width
ns
FSYNC Rise/Fall Time
ns
SYNCO Phase Shift from DH Rising
R
FSYNC
= 18.2kΩ, free-running mode,
at maximum duty cycle
Degrees
SYNCO Output Low Level I
SYNCO
= 5mA 0.4 V
SYNCO Output High Level I
SYNCO
= 5mA
V
MOSFET DRIVERS
(V
BST
- VLX) = 5V 1 2.5
DH On-Resistance, High State
(V
BST
- VLX) = 3V 1.2
Ω
(V
BST
- VLX) = 5V 1 2.5
DH On-Resistance, Low State
(V
BST
- VLX) = 3V 1.2
Ω
V
VL
= 5V 1 2.5
DL On-Resistance, High State
V
VL
= 3V 1.2
Ω
V
VL
= 5V 0.6 1.7
DL On-Resistance, Low State
V
VL
= 3V 0.8
Ω
Low-side off to high-side on 55
Break-Before-Make Dead Time
High-side off to low-side on 40
ns
LX, BST, IN Leakage Current V
BST
= 18.7V, VLX = 13.2V, VIN = 13.2V 5 µA
THERMAL PROTECTION
Thermal Shutdown Rising temperature
°C
Thermal-Shutdown Hysteresis 15 °C
38.5
56.5
100 115
127.5 150 172.5
170 200 230
-42.5
-57.5
-160 -200 -240
-110 -130 -150
800 1000 1200
200
150 220 270
160
100
100
165 180 195
V
- 1V
VL
+40
13.2
145
1200
100
+160
MAX8543/MAX8544
Step-Down Controllers with Prebias Startup,
Lossless Sensing, Synchronization, and OVP
4 _______________________________________________________________________________________
ELECTRICAL CHARACTERISTICS (continued)
(VIN= 13.2V, V
BST
- VLX= 5V, TA= 0°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.)
PARAMETER CONDITIONS
MIN
TYP
MAX
UNITS
POK
Power-OK Threshold
V
FB
rising, percent of V
OUT
,
typical hysteresis is 3%
88 91 94 %
POK Output Voltage, Low V
FB
= 0.6V, I
POK
= 2mA 25
mV
POK Leakage Current, High V
POK
= 5.5V
1 µA
OVERVOLTAGE PROTECTION (OVP)
Output Overvoltage Fault-Trip level
Rising edge compared to regulation set point;
triggers after one or two clock cycles
%
MODE CONTROL
MODE Logic-Level Low 3V ≤ V
VL
≤ 5.5V 0.4 V
MODE Logic-Level High 3V ≤ V
VL
≤ 5.5V
1.8 V
V
MODE
= 0V -1 +1
MODE Input Current
MODE = VL 5 10
µA
SHUTDOWN CONTROL
EN Logic-Level Low 3V ≤ V
VL
≤ 5.5V
V
EN Logic-Level High 3V ≤ V
VL
≤ 5.5V 2 V
V
EN
= 0 or 5.5V -1 +4
EN Input Current
V
EN
= 13.2V 1.5 6
µA
ELECTRICAL CHARACTERISTICS
(VIN= 13.2V, V
BST
- VLX= 5V, TA= -40°C to +85°C, unless otherwise noted.) (Note 2)
PARAMETER CONDITIONS
UNITS
Operating Input Voltage Range VL connected to IN for V
IN
< 5.5V 3.0
V
Quiescent Supply Current V
FB
= 0.9V, no switching 3 mA
10
Shutdown Supply Current
EN = GND, VL = IN, MODE = GND 20
µA
VL Undervoltage-Lockout Trip Level V
VL
rising, typical hysteresis is 80mV
V
Output Voltage Adjust Range (V
OUT
) (Note 1) 0.8 V
VL Output Voltage 5.5V < V
IN
< 13.2V, 1mA < IVL < 75mA 4.5 5.5 V
VL Output Current 75 mA
VOLTAGE REFERENCE
SS Shutdown Resistance From SS to GND, V
EN
= 0V 100 Ω
SS Soft-Start Current V
REF
= 0.625V 14 34 µA
ERROR AMPLIFIER
FB Regulation Voltage
V
Transconductance 70 160 µS
COMP Shutdown Resistance From COMP to GND, V
EN
= 0V 100 Ω
FB Input Leakage Current V
FB
= 0.9V 100 nA
FB Input Common-Mode Range
V
0.001
+110 +115 +120
200
0.45
MIN
EN = GND, MODE = GND, IN not connected to VL
2.52
0.788
-0.1
MAX
13.2
2.88
0.808
+0.9
MAX8543/MAX8544
Step-Down Controllers with Prebias Startup,
Lossless Sensing, Synchronization, and OVP
_______________________________________________________________________________________ 5
ELECTRICAL CHARACTERISTICS (continued)
(VIN= 13.2V, V
BST
- VLX= 5V, TA= -40°C to +85°C, unless otherwise noted.) (Note 2)
PARAMETER CONDITIONS
UNITS
CURRENT-SENSE AMPLIFIER
V
ILIM1
= 0V 8.8
4.8 7.2
3.2 4.8
Voltage Gain V
OUT
= 0 to 13V
V
ILIM1
= V
VL
2.4 3.6
V / V
CURRENT LIMIT
ILIM2 Output Current (MAX8544 Only) R
ILIM2
= 50kΩ to 200kΩ 4.2 5.5 µA
ILIM1 Input Current V
ILIM1
= 0V or V
VL
-1 +1 µA
V
CS+
- V
CS-, VILIM1
= 0V
V
CS+
- V
CS-, VILIM1
= (1/3)V
VL
85 115
V
CS+
- V
CS-
, V
ILIM1
= (2/3)V
VL
V
CS+
- V
CS-, VILIM1
= V
VL
230
V
LX
- V
PGND
, R
ILIM2
= 50kΩ (MAX8544 only) -40 -60
V
LX
- V
PGND
, R
ILIM2
= 200kΩ (MAX8544 only)
V
LX
- V
PGND
, VFB = 0.8V (MAX8543 only)
Current-Limit Threshold
V
LX
- V
PGND
, VFB = 0V (MAX8543 only) -20 -40
mV
Negative Current-Limit Threshold % of positive-direction current limit V
LX
- V
PGND
-25 -85 %
CS+, CS- Input Current V
CS+
= V
CS-
= 0V or 5V -40
µA
CS+, CS- Input Common-Mode Range 0
V
OSCILLATOR
Switching Frequency R
FSYNC
= 18.2kΩ
kHz
Minimum Off-Time Measured at DH
270 ns
Minimum On-Time Measured at DH 140 ns
FSYNC Synchronization Range
kHz
FSYNC Input High Pulse Width
ns
FSYNC Input Low Pulse Width
ns
FSYNC Rise/Fall Time 100 ns
SYNCO Phase Shift from DH Rising R
FSYNC
= 18.2kΩ
195
Degrees
SYNCO Output Low Level I
SYNCO
= 5mA 0.4 V
SYNCO Output High Level I
SYNCO
= 5mA
V
MOSFET DRIVERS
DH On-Resistance, High State (V
BST
- VLX) = 5V 2.5 Ω
DH On-Resistance, Low State (V
BST
- VLX) = 5V 2.5 Ω
DL On-Resistance, High State V
VL
= 5V 2.5 Ω
DL On-Resistance, Low State V
VL
= 5V 1.7 Ω
LX, BST, IN Leakage Current V
BST
= 18.7V, VLX = 13.2V, VIN = 13.2V 5 µA
V
V
ILIM1
ILIM1
= (1/3)V
= (2/3)V
MIN
VL
VL
38.5
127.5
170
-160
-110
800
150
160
100
100
165
V
- 1V
VL
MAX
13.2
56.5
172.5
-240
-150
+40
13.2
1200
1200
MAX8543/MAX8544
Step-Down Controllers with Prebias Startup,
Lossless Sensing, Synchronization, and OVP
6 _______________________________________________________________________________________
ELECTRICAL CHARACTERISTICS (continued)
(VIN= 13.2V, V
BST
- VLX= 5V, TA= -40°C to +85°C, unless otherwise noted.) (Note 2)
PARAMETER CONDITIONS
UNITS
POK
Power-OK Threshold
V
FB
rising, percent of V
OUT
,
typical hysteresis is 3%
88 94 %
POK Output Voltage, Low V
FB
= 0.6V, I
POK
= 2mA 200 mV
POK Leakage Current, High V
POK
= 5.5V 1 µA
OVERVOLTAGE PROTECTION (OVP)
Output Overvoltage Fault-Trip level
Rising edge compared to regulation set point;
triggers after one or two clock cycles
%
MODE CONTROL
MODE Logic-Level Low 3V ≤ V
VL
≤ 5.5V
0.4 V
MODE Logic-Level High 3V ≤ V
VL
≤ 5.5V
1.8 V
V
MODE
= 0V -1 +1
MODE Input Current
MODE = VL 10
µA
SHUTDOWN CONTROL
EN Logic-Level Low 3V ≤ V
VL
≤ 5.5V
V
EN Logic-Level High 3V ≤ V
VL
≤ 5.5V
2 V
V
EN
= 0V or 5.5V -1 +4
EN Input Current
V
EN
= 13.2V 6
µA
Note 1: Maximum output voltage is limited by maximum duty cycle and external components.
Note 2: Specifications to -40°C are guaranteed by design and not production tested.
MIN
MAX
+110
+120
0.45
MAX8543/MAX8544
Step-Down Controllers with Prebias Startup,
Lossless Sensing, Synchronization, and OVP
_______________________________________________________________________________________ 7
EFFICIENCY vs. LOAD CURRENT
WITH 12V INPUT
MAX8543 toc01
LOAD CURRENT (A)
EFFICIENCY (%)
101
10
20
30
40
50
60
70
80
90
100
0
0.1 100
V
OUT
= 3.3V
V
OUT
= 2.5V
V
OUT
= 1.8V
fS = 600kHz
EFFICIENCY vs. LOAD CURRENT
WITH 3.3V INPUT
MAX8543 toc02
LOAD CURRENT (A)
EFFICIENCY (%)
101
10
20
30
40
50
60
70
80
90
100
0
0.1 100
V
OUT
= 2.5V
V
OUT
= 1.8V
fS = 500kHz
V
OUT
= 1.5V
LOAD REGULATION WITH 12V INPUT
MAX8543 toc03
LOAD CURRENT (A)
OUTPUT VOLTAGE (V)
12963
2.46
2.47
2.48
2.49
2.50
2.51
2.52
2.53
2.54
2.55
2.45
015
LINE REGULATION WITH 12V INPUT
AND 2.5V OUTPUT
MAX8543 toc04
INPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
12.612.011.4
2.492
2.494
2.496
2.498
2.500
2.502
2.504
2.506
2.508
2.510
2.490
10.8 13.2
NO LOAD
15A LOAD
LINE REGULATION
3.0V TO 3.6V INPUT
MAX8543 toc05
INPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
3.53.43.33.23.1
2.44
2.46
2.48
2.50
2.52
2.54
2.42
3.0 3.6
NO LOAD
15A LOAD
f
S
= 350kHz
15A LOAD
f
S
= 500kHz
OSCILLATOR FREQUENCY
vs. INPUT VOLTAGE
MAX8543 toc06
INPUT VOLTAGE (V)
OSCILLATOR FREQUENCY (kHz)
5.04.54.03.5
420
440
460
480
500
520
540
560
580
600
400
3.0 5.5
TA = +85°C
TA = +25°C
TA = -40°C
R6 = 53.6k
Ω
OSCILLATOR FREQUENCY
vs. INPUT VOLTAGE
MAX8543 toc07
INPUT VOLTAGE (V)
OSCILLATOR FREQUENCY (kHz)
11.59.57.5
520
540
560
580
600
620
640
660
680
700
500
5.5 13.5
R6 = 42.2kΩ
TA = +85°C
TA = -40°C
TA = +25°C
Typical Operating Characteristics
(TA = +25°C, unless otherwise noted.)
MAX8543/MAX8544
Step-Down Controllers with Prebias Startup,
Lossless Sensing, Synchronization, and OVP
8 _______________________________________________________________________________________
Typical Operating Characteristics (continued)
(TA = +25°C, unless otherwise noted.)
MAX8544 STEP-LOAD RESPONSE
7.5A TO 15A TO 7.5A (5A/μs)
MAX8543 toc08
V
OUT
I
OUT
50mV/div
AC-COUPLED
0
5A/div
10μs/div
MAX8544 STEP-LOAD RESPONSE
1.5A TO 15A TO 1.5A (5A/μs)
MAX8543 toc09
V
OUT
I
OUT
100mV/div
AC-COUPLED
0
5A/div
10μs/div
MAX8544 POWER-UP WAVEFORMS
MAX8543 toc10
V
IN
V
POK
5V/div
0
10A/div
2ms/div
V
OUT
I
L
2V/div
5V/div
MAX8544 POWER-DOWN WAVEFORMS
MAX8543 toc11
V
IN
V
POK
5V/div
0
10A/div
2ms/div
V
OUT
I
L
2V/div
2V/div
MAX8543 POWER-UP WAVEFORMS
MAX8543 toc12
V
IN
2V/div
0
10A/div
2ms/div
V
OUT
I
L
1V/div
MAX8543 POWER-DOWN WAVEFORMS
MAX8543 toc13
V
IN
2V/div
0
10A/div
2ms/div
V
OUT
I
L
1V/div
MAX8543/MAX8544
Step-Down Controllers with Prebias Startup,
Lossless Sensing, Synchronization, and OVP
_______________________________________________________________________________________ 9
MAX8544 ENABLE WAVEFORMS
MAX8543 toc14
V
EN
5V/div
0
10A/div
2ms/div
V
OUT
I
L
2V/div
V
POK
5V/div
FSYNC AND SYNCO WAVEFORMS
MAX8543 toc15
V
OUT
1V/div
5V/div
2μs/div
V
LX
V
SYNCO
10V/div
V
FSYNC
5V/div
SHORT CIRCUIT AND RECOVERY
MAX8543 toc16
V
IN
10V/div
12V
0
1ms/div
V
OUT
I
IN
1V/div
I
L
10A/div
0
10A/div
OVERVOLTAGE PROTECTION
WITH 15A LOAD
MAX8543 toc17
V
OUT
5V/div
40μs/div
V
DH
V
DL
1V/div
10V/div
0V
0V
5V
5V
PREBIASED STARTUP
(OUTPUT PREBIASED AT 1.5V)
MAX8543 toc18
V
IN
5V/div
1ms/div
V
LX
V
DL
2.5V
10V/div
V
OUT
5V/div
500mV/div
1.5V
Typical Operating Characteristics (continued)
(TA = +25°C, unless otherwise noted.)
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