MAXIM MAX8597, MAX8598, MAX8599 Technical data
General Description
The MAX8597/MAX8598/MAX8599 voltage-mode PWM
step-down controllers are designed to operate from a
4.5V to 28V input supply and generate output voltages
down to 0.6V. A proprietary switching algorithm stretches the duty cycle to >99.5% for low-dropout design.
Unlike conventional step-down regulators using a pchannel high-side MOSFET to achieve high duty cycle,
the MAX8597/MAX8598/MAX8599 drive n-channel
MOSFETs resulting in high efficiency and high-currentcapability designs.
The MAX8597 is available in a 20-pin thin QFN package and is designed for applications that use an analog
signal to control the output voltage with an adjustable
offset, such as DC fan-speed control. This is achieved
with an internal uncommitted operational amplifier. The
MAX8597 is also targeted for tracking output-voltage
applications for chipsets, ASIC and DSP cores, and I/O
supplies. The MAX8598/MAX8599 are available in a 16pin thin QFN package and do not have the uncommitted
operational amplifier, reference input, and reference output, but offer an open-drain, power-OK output.
The MAX8597/MAX8598/MAX8599 allow startup with
prebias voltage on the output for applications where a
backup supply or a tracking device may charge the
output capacitor before the MAX8597/MAX8598/
MAX8599 are enabled. In addition, the MAX8599 features output overvoltage protection.
These controllers also feature lossless high-side peak
inductor current sensing, adjustable current limit, and
hiccup-mode short-circuit protection. Switching frequency is set with an external resistor from 200kHz to
1.4MHz. This wide frequency range combined with a
wide-bandwidth error amplifier enables the loop compensation scheme to give the user ample flexibility to
optimize for cost, size, and efficiency.
Applications
Nonisolated Power Modules
Variable-Speed DC Fan Power Supplies
(MAX8597)
Tracking Power Supplies (MAX8597)
Chipset Power Supplies
Features
♦ Low Dropout with >99.5% Duty Cycle
♦ Lossless High-Side Current Limit
♦ Wide 4.5V to 28V Input Range
♦ Dynamic Output Voltage Adjustment with
Adjustable Offset (MAX8597)
♦ Remote Voltage Sensing for Both Positive and
Negative Rails (MAX8597)
♦ Tracking Output Through REFIN (MAX8597)
♦ Adjustable Switching Frequency from 200kHz to
1.4MHz
♦ Adjustable Soft-Start
♦ Prebias Startup
♦ Enable and Power-OK (MAX8598/MAX8599) for
Flexible Sequencing
♦ 25MHz Error Amplifier
♦ Adjustable Hiccup Current Limit for Output
Short-Circuit Protection
♦ Output Overvoltage Protection (MAX8599)
♦ Small, Low-Profile Thin QFN Package
MAX8597/MAX8598/MAX8599
Low-Dropout, Wide-Input-Voltage,
Step-Down Controllers
________________________________________________________________ Maxim Integrated Products 1
Ordering Information
19-3505; Rev 1; 6/05
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.
EVALUATION KIT
AVAILABLE
+Denotes lead-free package.
Pin Configurations appear at end of data sheet.
PART TEMP RANGE PIN-PACKAGE
MAX8597ETP -40°C to +85°C
MAX8597ETP+ -40°C to +85°C
MAX8598ETE -40°C to +85°C
MAX8598ETE+ -40°C to +85°C
MAX8599ETE -40°C to +85°C
MAX8599ETE+ -40°C to +85°C
20 Thin QFN 4mm x 4mm
(T2044-3)
20 Thin QFN 4mm x 4mm
(T2044-3)
16 Thin QFN 4mm x 4mm
(T1644-4)
16 Thin QFN 4mm x 4mm
(T1644-4)
16 Thin QFN 4mm x 4mm
(T1644-4)
16 Thin QFN 4mm x 4mm
(T1644-4)
MAX8597/MAX8598/MAX8599
Low-Dropout, Wide-Input-Voltage,
Step-Down Controllers
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(VV+= VVL= V
AVL
= VEN= V
REFIN
= 5V, V
BST
= 6V, VLX= 1V, CVL= 4.7µF, C
REFOUT
= 1µF, V
AIN-
= V
AOUT
, V
AIN+
= 2.5V, V
ILIM
=
V
LX
- 0.2V, VFB= 0.65V, GND = PGND = 0V, CSS= 0.01µF, R
FREQ
= 20kΩ, TA= 0°C to +85°C, typical values are at TA= +25°C,
unless otherwise noted.)
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.
V+, ILIM to GND .....................................................-0.3V to +30V
AVL, VL to GND........................................................-0.3V to +6V
PGND to GND .......................................................-0.3V to +0.3V
FB, EN, POK, AIN-, AIN+, REFIN to GND ................-0.3V to +6V
AOUT, REFOUT, FREQ, SS, COMP to
GND .....................................................-0.3V to (V
AVL
+ 0.3V)
BST to GND ............................................................-0.3V to +36V
DH to LX....................................................-0.3V to (V
BST
+ 0.3V)
LX to GND ........................-2V (-2.5V for less than 50ns) to +30V
LX to BST..................................................................-6V to +0.3V
DL to PGND.................................................-0.3V to (V
VL
+ 0.3V)
Continuous Power Dissipation
16- or 20-Pin Thin QFN
Up to +70°C (derate 16.9mW/°C above +70°C)........1349mW
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 MIN TYP MAX UNITS
GENERAL
V+ Operating Range 5.5 28.0 V
V+/VL Operating Range V+ = VL 4.5 5.5 V
V+ Operating Supply Current V
V+ Standby Supply Current V
= 12V, VL unloaded, no MOSFETs connected, VFB = 0V 3.4 5.0 mA
V+
= 12V, VL unloaded, VFB = 0V 2.0 mA
V+
VL REGULATOR
Output Voltage 5.5V < V
VL Undervoltage-Lockout
Trip Level
Rising edge, typical hysteresis = 460mV 4.05 4.2 4.35 V
< 28V, 1mA < I
V+
Thermal Shutdown Rising temperature, typical hysteresis = 10°C +160 °C
REFERENCE (MAX8597 only)
REFOUT Output Voltage I
REFOUT Load Regulation I
REFOUT Internal Discharge
Switch On-Resistance
= 150µA, VV+ = VVL = 4.5V or 5.5V 2.49 2.50 2.51 V
REFOUT
= 10µA to 1mA 10 mV
REFOUT
During VL UVLO 15 Ω
CURRENT-LIMIT COMPARATOR (all current limits are tested at V
ILIM Sink Current 1.8V < V
Comparator Input Offset
Voltage Error
SOFT-START
Soft-Start Source Current V
Soft-Start Sink Current V
FREQUENCY
V
LX
SS
SS
R
FREQ
R
FREQ
R
FREQ
< 28V, V
LX
= 28V, V
= 100mV 3 5 7 µA
= (0.6V or V
BST
= 100kΩ 150 200 240
= 20.0kΩ 800 1000 1200Frequency
= 14.3kΩ 1100 1400 1700
= VLX + 5V 180 200 220 µA
BST
= VLX + 5V -10 +10 mV
) 3 5 7 µA
REFIN
< 35mA 4.7 5.0 5.3 V
LOAD
= VVL = 4.5V and 5.5V)
V+
kHz
MAX8597/MAX8598/MAX8599
Low-Dropout, Wide-Input-Voltage,
Step-Down Controllers
_______________________________________________________________________________________ 3
ELECTRICAL CHARACTERISTICS (continued)
(VV+= VVL= V
AVL
= VEN= V
REFIN
= 5V, V
BST
= 6V, VLX= 1V, CVL= 4.7µF, C
REFOUT
= 1µF, V
AIN-
= V
AOUT
, V
AIN+
= 2.5V, V
ILIM
=
V
LX
- 0.2V, VFB= 0.65V, GND = PGND = 0V, CSS= 0.01µF, R
FREQ
= 20kΩ, TA= 0°C to +85°C, typical values are at TA= +25°C,
unless otherwise noted.)
DH Minimum Off-Time 180 200 220 ns
DH Minimum On-Time 115 140 ns
PARAMETER CONDITIONS MIN TYP MAX UNITS
FB ERROR AMPLIFIER
FB Input Bias Current 100 nA
FB Input Voltage Set Point Over load and line 0.594 0.600 0.606 V
FB Offset Error V
Error-Amp Open-Loop Voltage
Gain
Slew Rate C
UNCOMMITTED OPERATIONAL AMPLIFIER (MAX8597 only)
Open-Loop Voltage Gain (A
Output-Voltage Swing High V
Output-Voltage Swing Low V
Unity-Gain BW 1.5 MHz
Phase Margin
Slew Rate C
Input Offset Voltage VCM = 1.25V and 2.5V -3 +3 mV
Input Leakage Current -10 +10 nA
Input Common-Mode Range
(CMVR)
Common-Mode Rejection Ratio
(CMRR)
VOL
)
= 1.25V and 2.5V, measured with respect to REFIN +10 -10 mV
REFIN
= 1.2V to 2.4V 72 90 dB
V
COMP
= 80pF 18 V/µs
LOAD
R
= 100kΩ 90
LOAD
R
= 10kΩ 70
LOAD
V
-
= 2.5V, V
AIN+
= 2.5V, V
AIN+
C
= 10pF, R
LOAD
= 100pF, R
C
LOAD
= 100pF 3.5 V/µs
LOAD
AIN
AIN
- = (V
- = (V
LOAD
LOAD
- 100mV), I
AIN+
+ 100mV), I
AIN+
= 10kΩ to 100kΩ +80
= 10kΩ to 100kΩ +40
= 100µA
SOURCE
= 100µA 20 mV
SINK
AVL
20mV
+0.50
75 dB
V
AVL
2.0
D egr ees
-
DRIVERS
DH, DL Break-Before-Make Time C
DH On-Resistance in Low State V
DH On-Resistance in High State V
DL On-Resistance in Low State V
DL On-Resistance in High State V
BST Bias Current V
LX Bias Current V
BST/LX Leakage Current V
= 2000pF 20 ns
LOAD
- VLX = 5V 1.0 2.5 Ω
BST
- VLX = 5V 1.5 3.3 Ω
BST
= VV+ = 5V 0.45 1.0 Ω
VL
= VV+ = 5V 1.3 2.5 Ω
VL
= 33V, VLX = 28V, VEN = 0V 230 520 µA
BST
= 33V, VLX = 28V, VEN = 0V -230 -520 µA
BST
= VLX = 28V, VEN = 0V 50 µA
BST
LOGIC INPUTS (EN)
Input Low Level 4.5V < V
Input High Level 4.5V < V
Input Bias Current V
VL
= VV+ = V
VL
= VV+ = V
VL
= VV+ = V
< 5.5V 1.14 0.80 V
AVL
< 5.5V 2.40 1.73 V
AVL
= 5.5V, VEN = 0 to 5.5V -1 +1 µA
AVL
dB
V
V
MAX8597/MAX8598/MAX8599
Low-Dropout, Wide-Input-Voltage,
Step-Down Controllers
4 _______________________________________________________________________________________
ELECTRICAL CHARACTERISTICS (continued)
(VV+= VVL= V
AVL
= VEN= V
REFIN
= 5V, V
BST
= 6V, VLX= 1V, CVL= 4.7µF, C
REFOUT
= 1µF, V
AIN-
= V
AOUT
, V
AIN+
= 2.5V, V
ILIM
=
V
LX
- 0.2V, VFB= 0.65V, GND = PGND = 0V, CSS= 0.01µF, R
FREQ
= 20kΩ, TA= 0°C to +85°C, typical values are at TA= +25°C,
unless otherwise noted.)
ELECTRICAL CHARACTERISTICS
(VV+= VVL= V
AVL
= VEN= V
REFIN
= 5V, V
BST
= 6V, VLX= 1V, CVL= 4.7µF, C
REFOUT
= 1µF, V
AIN-
= V
AOUT
, V
AIN+
= 2.5V, V
ILIM
=
V
LX
- 0.2V, VFB= 0.65V, GND = PGND = 0V, CSS= 0.01µF, R
FREQ
= 20kΩ, TA= -40°C to +85°C, typical values are at TA= +25°C,
unless otherwise noted.) (Note 1)
Dual Mode is a trademark of Maxim Integrated Products, Inc.
PARAMETER CONDITIONS MIN TYP MAX UNITS
REFIN INPUT (MAX8597 only)
REFIN Input Voltage Range 0 2.75 V
REFIN Dual Mode™ Threshold
REFIN Input Bias Current V
OV AND UV FAULT COMPARATORS
Upper FB Fault Threshold (OV) Rising edge, hysteresis = 15mV (MAX8599 only) 115 117 120 %
Lower FB Fault Threshold (UV) Falling edge, hysteresis = 15mV 67 70 73 %
POWER-OK OUTPUT (POK) (MAX8598/MAX8599 only)
POK Delay For both FB rising and falling edges 8
Lower FB POK Threshold FB falling, hysteresis = 20mV 85 88 90 %
POK Output Low Level I
POK Output High Leakage V
REFIN
SINK
POK
= 1.25V or 2.5V -250 +250 nA
= 2mA 0.4 V
= 5.5V 5 µA
V
AVL
1.0
-
V
AVL
-
0.5
Clock
cycles
V
PARAMETER CONDITIONS MIN TYP MAX UNITS
GENERAL
V+ Operating Range 5.5 28.0 V
V+/VL Operating Range V+ = VL 4.5 5.5 V
V+ Operating Supply Current V
= 12V, VL unloaded, no MOSFETs connected, VFB = 0V 5.0 mA
V+
VL REGULATOR
Output Voltage 5.5V < V
VL Undervoltage-Lockout Trip
Level
REFERENCE (MAX8597 only)
REFOUT Output Voltage I
REFOUT Load Regulation I
Rising edge, typical hysteresis = 460mV 4.05 4.35 V
REFOUT
REFOUT
CURRENT-LIMIT COMPARATOR (all current limits are tested at V
ILIM Sink Current V
Comparator Input Offset Voltage
Error
SOFT-START
Soft-Start Source Current V
Soft-Start Sink Current V
ILIM
-10 +10 mV
SS
SS
< 28V, 1mA < I
V+
= 150µA, VV+ = VVL = 4.5V or 5.5V 2.47 2.51 V
= 10µA to 1mA 10 mV
= V
- 0.2V, 1.8V < VLX < 28V, V
LX
= 100mV 3 7 µA
= (0.6V or V
) 3 7 µA
REFIN
< 35mA 4.7 5.3 V
LOAD
= VVL = 4.5V and 5.5V)
V+
BST
= V
LX
+ 5V
180 220 µA
MAX8597/MAX8598/MAX8599
Low-Dropout, Wide-Input-Voltage,
Step-Down Controllers
_______________________________________________________________________________________ 5
ELECTRICAL CHARACTERISTICS (continued)
(VV+= VVL= V
AVL
= VEN= V
REFIN
= 5V, V
BST
= 6V, VLX= 1V, CVL= 4.7µF, C
REFOUT
= 1µF, V
AIN-
= V
AOUT
, V
AIN+
= 2.5V, V
ILIM
=
V
LX
- 0.2V, VFB= 0.65V, GND = PGND = 0V, CSS= 0.01µF, R
FREQ
= 20kΩ, TA= -40°C to +85°C, typical values are at TA= +25°C,
unless otherwise noted.) (Note 1)
FREQUENCY
DH Minimum Off-Time 180 230 ns
DH Minimum On-Time 140 ns
PARAMETER CONDITIONS MIN TYP MAX UNITS
R
FREQ
R
FREQ
R
FREQ
= 100kΩ 140 240
= 20.0kΩ 800 1200Frequency
= 14.3kΩ 1100 1700
kHz
FB ERROR AMPLIFIER
FB Input Bias Current 150 nA
FB Input Voltage Set Point Over load and line 0.591 0.606 V
FB Offset Error V
Error-Amp Open-Loop Voltage
Gain
UNCOMMITTED OPERATIONAL AMPLIFIER (MAX8597 only)
Output Voltage Swing High V
Output Voltage Swing Low V
Input Offset Voltage VCM = 1.25V and 2.5V -3 +3 mV
Input Common-Mode Range
(CMVR)
= 1.25V and 2.5V, measured with respect to REFIN +20 -20 mV
REFIN
= 1.2V to 2.4V 72 dB
V
COMP
V
-
AIN+
AIN+
= 2.5V, V
= 2.5V, V
AIN
AIN
- = (V
- = (V
- 100mV), I
AIN+
+ 100mV), I
AIN+
= 100µA
SOURCE
= 100µA 20 mV
SINK
AVL
20mV
+0.50
V
AVL
2.0
-
DRIVERS
DH On-Resistance in Low State V
DH On-Resistance in High State V
DL On-Resistance in Low State V
DL On-Resistance in High State V
BST Bias Current V
LX Bias Current V
BST/LX Leakage Current V
- VLX = 5V 2.5 Ω
BST
- VLX = 5V 3.3 Ω
BST
= V
VL
VL
BST
BST
BST
= 5V 1.0 Ω
V+
= VV+ = 5V 3.5 Ω
= 33V, VLX = 28V, VEN = 0V 520 µA
= 28V, V
LX
= 28V, V
LX
= 0V -520 µA
EN
= 0V 50 µA
EN
= 33V, V
= V
LOGIC INPUTS (EN)
Input Low Level 4.5V < V
Input High Level 4.5V < V
Input Bias Current V
= VV+ = V
VL
VL
VL
= V
= V
= V
V+
V+
AVL
< 5.5V 0.8 V
AVL
= V
< 5.5V 2.4 V
AVL
= 5.5V, VEN = 0 to 5.5V -1 +1 µA
REFIN INPUT (MAX8597 only)
REFIN Input Voltage Range 0 2.75 V
V
REFIN Dual-Mode Threshold
REFIN Input Bias Current V
-
AVL
1.0
= 1.25V or 2.5V -250 +250 nA
REFIN
V
-
AVL
0.5
V
V
V
MAX8597/MAX8598/MAX8599
Low-Dropout, Wide-Input-Voltage,
Step-Down Controllers
6 _______________________________________________________________________________________
Note 1: Limits to -40°C are guaranteed by design and characterization.
ELECTRICAL CHARACTERISTICS (continued)
(VV+= VVL= V
AVL
= VEN= V
REFIN
= 5V, V
BST
= 6V, VLX= 1V, CVL= 4.7µF, C
REFOUT
= 1µF, V
AIN-
= V
AOUT
, V
AIN+
= 2.5V, V
ILIM
=
V
LX
- 0.2V, VFB= 0.65V, GND = PGND = 0V, CSS= 0.01µF, R
FREQ
= 20kΩ, TA= -40°C to +85°C, typical values are at TA= +25°C,
unless otherwise noted.) (Note 1)
Typical Operating Characteristics
(Circuit of Figure 4, TA= +25°C, 500kHz switching frequency, VIN= 12V, unless otherwise noted.)
PARAMETER CONDITIONS MIN TYP MAX UNITS
OV AND UV FAULT COMPARATORS
Upper FB Fault Threshold (OV) Rising edge, hysteresis = 15mV (MAX8599 only) 115 120 %
Lower FB Fault Threshold (UV) Falling edge, hysteresis = 15mV 67 73 %
POWER-OK OUTPUT (POK) (MAX8598/MAX8599 only)
Lower FB POK Threshold FB falling, hysteresis = 20mV 85 90 %
POK Output Low Level I
POK Output High Leakage V
EFFICIENCY vs. LOAD CURRENT
100
V
OUT
95
V
90
85
V
80
75
EFFICIENCY (%)
70
65
60
0.1 10
CIRCUIT OF FIGURE 1
= 11.5V
= 9V
OUT
= 6V
OUT
1
LOAD CURRENT (A)
SINK
POK
= 2mA 0.4 V
= 5.5V
100
MAX8597 toc01
EFFICIENCY (%)
EFFICIENCY vs. LOAD CURRENT
CIRCUIT OF FIGURE 2
MAX8597 toc02
1.210
1.205
1.200
OUTPUT VOLTAGE (V)
1.195
1.190
020
V
= 3.3V
OUT
90
80
70
60
50
40
30
1100
V
LOAD CURRENT (A)
OUT
V
OUT
= 1.2V
= 1.8V
10
V
= 2.5V
OUT
OUTPUT VOLTAGE
vs. LOAD CURRENT
I
(A)
LOAD
5
18161412108642
µA
MAX8597 toc03
OUTPUT VOLTAGE
1.210
vs. INPUT VOLTAGE
1.205
I
LOAD
1.200
OUTPUT VOLTAGE (V)
1.195
1.190
10.0 14.0
VIN (V)
I
LOAD
= 0A
= 20A
POWER-UP WAVEFORMS
V
AVL
MAX8597 toc04
I
LX
V
OUT
V
IN
13.513.012.512.011.511.010.5
2ms/div
MAX8597 toc05
5V/div
10A/div
1V/div
10V/div
V
I
POWER-DOWN WAVEFORMS
AVL
I
LX
OUT
V
IN
MAX8597 toc06
5V/div
10A/div
1V/div
10V/div
2ms/div
MAX8597/MAX8598/MAX8599
Low-Dropout, Wide-Input-Voltage,
Step-Down Controllers
_______________________________________________________________________________________ 7
Typical Operating Characteristics (continued)
(Circuit of Figure 4, TA= +25°C, 500kHz switching frequency, VIN= 12V, unless otherwise noted.)
OUTPUT PREBIASED STARTUP
V
LX
V
OUT
V
IN
V
DL
OUTPUT VOLTAGE vs. V
1ms/div
MAX8597 toc07
10V/div
1.2V
1.0V
5V/div
5V/div
ADJ
(VIN = 12V)
13
12
11
10
9
8
7
OUTPUT VOLTAGE (V)
6
5
4
06
CIRCUIT OF FIGURE 1
= 1.2Ω
R
LOAD
V
(V)
ADJ
MAX8597 toc09
54321
V
V
OUT
V
V
V
COMP
(AC-COUPLED)
STARTUP/SHUTDOWN WITH
EN (I
POK
I
LX
EN
ENTERING DROPOUT WAVEFORMS
CIRCUIT OF FIGURE 1
V
LX
OUT
V
IN
LOAD
2ms/div
2µs/div
= 20A)
MAX8597 toc08
5V/div
10A/div
1V/div
5V/div
MAX8597 toc10
10V/div
11V
500mV/div
100mV/div
V
V
OUT
V
COMP
V
(AC-COUPLED)
HEAVY-DROPOUT WAVEFORMS
CIRCUIT OF FIGURE 1
LX
IN
10µs/div
MAX8597 toc11
10V/div
11.9V
500mV/div
500mV/div
OUTPUT TRACKING REFIN
1ms RISE
TIME
5ms RISE
TIME
1ms/div
MAX8597 toc12
CIRCUIT OF FIGURE 3
V
REFIN
V
OUT
1V/div
V
REFIN
V
OUT
1V/div
MAX8597/MAX8598/MAX8599
Low-Dropout, Wide-Input-Voltage,
Step-Down Controllers
8 _______________________________________________________________________________________
Typical Operating Characteristics (continued)
(Circuit of Figure 4, TA= +25°C, 500kHz switching frequency, VIN= 12V, unless otherwise noted.)
50% LOAD STEP AT 5A/µs
MAX8597 toc13
40µs/div
50mV/div
V
OUT
(AC-COUPLED)
I
OUT
20A
10A
90% LOAD STEP AT 5A/µs
MAX8597 toc14
40µs/div
100mV/divV
OUT
(AC-COUPLED)
I
OUT
20A
2A
SHORT-CIRCUIT RESPONSE
MAX8597 toc15
4ms/div
1V/div
2A/div
V
OUT
I
IN
I
LX
10A/div
OUTPUT OVERVOLTAGE PROTECTION
MAX8597 toc16
10µs/div
500mV/div
10V/div
V
FB
V
DH
V
DL
5V/div
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