19-0739; Rev 1; 2/10
KIT
ATION
EVALU
BLE
AVAILA
Single Quick-PWM Step-Down
Controller with Dynamic REFIN
General Description
Features
o
Quick-PWM with Fast Transient Response
o
Supports Any Output Capacitor
No Compensation Required with
Polymers/Tantalum
Stable with Ceramic Output Capacitors Using
External Compensation
o
Precision 2V ±10mV Reference
o
Dynamically Adjustable Output Voltage
(0 to 0.9V
IN
Range)
Feedback Input Regulates to 0 to 2V REFIN
Voltage
0.5% V
OUT
Accuracy Over Line and Load
o
26V Maximum Input Voltage Rating
o
Adjustable Valley Current-Limit Protection
Thermal Compensation with NTC
Supports Foldback Current Limit
o
Resistively Programmable Switching Frequency
o
Overvoltage Protection
o
Undervoltage/Thermal Protection
o
Voltage Soft-Start and Soft-Shutdown
o
Monotonic Power-Up with Precharged Output
o
Power-Good Window Comparator
MAX8792
The MAX8792 pulse-width modulation (PWM) controller
provides high efficiency, excellent transient response,
and high DC-output accuracy needed for stepping
down high-voltage batteries to generate low-voltage
core or chipset/RAM bias supplies in notebook comput-
ers. The output voltage can be dynamically controlled
using the dynamic REFIN, which supports input volt-
ages between 0 to 2V. The REFIN adjustability com-
bined with a resistive voltage-divider on the feedback
input allows the MAX8792 to be configured for any out-
put voltage between 0 to 0.9V
IN
.
Maxim’s proprietary Quick-PWM™ quick-response, con-
stant-on-time PWM control scheme handles wide
input/output voltage ratios (low-duty-cycle applications)
with ease and provides 100ns “instant-on” response to
load transients while maintaining a relatively constant
switching frequency. Strong drivers allow the MAX8792
to efficiently drive large synchronous-rectifier MOSFETs.
The controller senses the current across the synchro-
nous rectifier to achieve a low-cost and highly efficient
valley current-limit protection. The adjustable current-
limit threshold provides a high degree of flexibility,
allowing thermally compensated protection using an
NTC or foldback current-limit protection using a volt-
age-divider derived from the output.
The MAX8792 includes a voltage-controlled soft-start
and soft-shutdown in order to limit the input surge cur-
rent, provide a monotonic power-up (even into a
precharged output), and provide a predictable power-
up time. The controller also includes output fault protec-
tion—undervoltage and overvoltage protection—as well
as thermal-fault protection.
The MAX8792 is available in a tiny 14-pin, 3mm x 3mm
TDFN package. For space-constrained applications,
refer to the MAX17016 single step-down with 10A, 26V
internal MOSFETs available in a small 40-pin, 6mm x
6mm TQFN package.
Applications
.
Notebook Computers
I/O and Chipset Supplies
GPU Core Supply
DDR Memory—VDDQ or VTT
Point-of-Load Applications
Step-Down Power Supply
Ordering Information
PART
PIN-PACKAGE
PKG
CODE
TOP
MARK
MAX8792ETD+T 14 TDFN-EP* 3mm x 3mm T1433-1 ADC
Note:
This device is specified over the -40°C to +85°C operating
temperature range.
+Denotes
a lead(Pb)-free/RoHS-compliant package.
Pin Configuration
PGOOD
SKIP
ILIM
9
V
CC
REF
FB
8
7
TON
TOP VIEW
14
13
12
11
10
MAX8792
REFIN
5
DH
GND
1
EN
2
V
DD
3
DL
4
LX
6
BST
Quick-PWM is a trademark of Maxim Integrated Products, Inc.
TDFN
(3mm x 3mm)
1
________________________________________________________________
Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
Single Quick-PWM Step-Down
Controller with Dynamic REFIN
MAX8792
ABSOLUTE MAXIMUM RATINGS
TON to GND ...........................................................-0.3V to +28V
V
DD
to GND ..............................................................-0.3V to +6V
V
CC
to GND ................................................-0.3V to (V
DD
+ 0.3V)
EN,
SKIP,
PGOOD to GND.......................................-0.3V to +6V
REF, REFIN to GND ....................................-0.3V to (V
CC
+ 0.3V)
ILIM, FB to GND .........................................-0.3V to (V
CC
+ 0.3V)
DL to GND ..................................................-0.3V to (V
DD
+ 0.3V)
BST to GND .................................................(V
DD
- 0.3V) to +34V
BST to LX..................................................................-0.3V to +6V
BST to V
DD
.............................................................-0.3V to +28V
DH to LX ....................................................-0.3V to (V
BST
+ 0.3V)
REF Short Circuit to GND ...........................................Continuous
Continuous Power Dissipation (T
A
= +70°C)
14-Pin 3mm x 3mm TDFN
(derated 24.4mW/°C above +70°C)....................1951mW
Operating Temperature Range (extended) .........-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature.........................................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Soldering Temperature (reflow) .......................................+240°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
(Circuit of Figure 1, V
IN
= 12V, V
DD
= V
CC
= V
EN
= 5V, REFIN = ILIM = REF,
SKIP
= GND. T
A
=
0°C to +85°C,
unless otherwise spec-
ified. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
PWM CONTROLLER
Input Voltage Range
Quiescent Supply Current (V
DD
)
Shutdown Supply Current (V
DD
)
V
DD
-to-V
CC
Resistance
On-Time
Minimum Off-Time
TON Shutdown Supply Current
REFIN Voltage Range
FB Voltage Range
V
REFIN
V
FB
V
IN
I
DD
+ I
CC
I
SHDN
R
CC
t
ON
t
OFF(MIN)
V
IN
= 12V,
V
FB
= 1.0V
(Note 3)
(Note 3)
EN = GND, V
TON
= 26V,
V
CC
= 0V or 5V, T
A
= +25°C
(Note 2)
(Note 2)
V
REFIN
= 0.5V, T
A
= +25°C
measured at FB,
V
IN
= 2V to 26V, T
A
= 0°C to +85°C
SKIP
= V
DD
V
REFIN
= 1.0V
V
REFIN
= 2.0V
FB Input Bias Current
Load-Regulation Error
Line-Regulation Error
Soft-Start/-Stop Slew Rate
Dynamic REFIN Slew Rate
REFERENCE
Reference Voltage
V
REF
V
CC
= 4.5V
to 5.5V
No load
I
REF
= -10μA to +50μA
1.990
1.98
2.00
2.010
2.02
V
t
SS
t
DYN
I
FB
T
A
= +25°C
T
A
= 0°C to +85°C
T
A
= 0°C to +85°C
0
0
0.495
0.493
0.995
0.993
1.990
-0.1
0.1
0.25
1
8
2.0
1.0
0.5
R
TON
= 97.5kΩ (600kHz)
R
TON
= 200kΩ (300kHz)
R
TON
= 302.5kΩ (200kHz)
118
250
354
FB forced above REFIN
EN = GND, T
A
= +25°C
2
0.7
0.1
20
139
278
417
200
0.01
160
306
480
300
1
V
REF
V
REF
0.505
0.507
V
1.005
1.007
2.010
+0.1
μA
%
%
mV/μs
mV/μs
ns
μA
V
V
ns
26
1.2
2
V
mA
μA
Ω
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
FB Voltage Accuracy
V
FB
V
FB
= 0.5V to 2.0V, T
A
= +25°C
I
LOAD
= 0 to 3A,
SKIP
= V
DD
V
CC
= 4.5V to 5.5V, V
IN
= 4.5V to 26V
Rising/falling edge on EN
Rising edge on REFIN
2
_______________________________________________________________________________________
Single Quick-PWM Step-Down
Controller with Dynamic REFIN
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, V
IN
= 12V, V
DD
= V
CC
= V
EN
= 5V, REFIN = ILIM = REF,
SKIP
= GND. T
A
=
0°C to +85°C,
unless otherwise spec-
ified. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
FAULT DETECTION
With respect to the internal target voltage
(error comparator threshold); rising edge;
hysteresis = 50mV
OVP
Dynamic transition
Minimum OVP threshold
Output Overvoltage
Fault-Propagation Delay
Output Undervoltage-Protection
Trip Threshold
Output Undervoltage
Fault-Propagation Delay
PGOOD Propagation Delay
PGOOD Output-Low Voltage
PGOOD Leakage Current
Dynamic REFIN Transition Fault
Blanking Threshold
Thermal-Shutdown Threshold
V
CC
Undervoltage Lockout
Threshold
CURRENT LIMIT
ILIM Input Range
Current-Limit Threshold
Current-Limit Threshold
(Negative)
Current-Limit Threshold
(Zero Crossing)
Ultrasonic Frequency
Ultrasonic Current-Limit Threshold
V
ILIMIT
V
INEG
V
ZX
V
ILIM
= 0.4V
ILIM = REF (2.0V)
V
ILIM
= 0.4V
V
ILIM
= 0.4V,
V
GND
- V
LX
,
SKIP
= GND or open
SKIP
= open (3.3V); V
FB
= V
REFIN
+ 50mV
SKIP
= open (3.3V); V
FB
= V
REFIN
+ 50mV
18
0.4
18
92
20
100
-24
1
30
35
V
REF
22
108
V
mV
mV
mV
kHz
mV
T
SHDN
V
UVLO(VCC)
I
PGOOD
t
OVP
FB forced 25mV above trip threshold
With respect to the internal target voltage
(error comparator threshold); falling edge;
hysteresis = 50mV
FB forced 25mV below trip threshold
UVP falling edge, 25mV overdrive
t
PGOOD
OVP rising edge, 25mV overdrive
Startup delay
I
SINK
= 3mA
FB = REFIN (PGOOD high impedance),
PGOOD forced to 5V, T
A
= +25°C
Fault blanking initiated; REFIN deviation
from the internal target voltage (error
comparator threshold); hysteresis = 10mV
Hysteresis = 15°C
Rising edge, PWM disabled below this
level; hysteresis = 100mV
3.95
±50
160
4.2
4.45
100
250
300
V
REF
+
0.30
0.7
5
μs
350
mV
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
MAX8792
Output Overvoltage-Protection
Trip Threshold
V
UVP
-240
-200
-160
mV
t
UVP
100
200
5
5
200
350
μs
μs
350
0.4
1
V
μA
mV
°C
V
_______________________________________________________________________________________
3
Single Quick-PWM Step-Down
Controller with Dynamic REFIN
MAX8792
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, V
IN
= 12V, V
DD
= V
CC
= V
EN
= 5V, REFIN = ILIM = REF,
SKIP
= GND. T
A
=
0°C to +85°C,
unless otherwise spec-
ified. Typical values are at T
A
= +25°C.) (Note 1)
PARAMETER
GATE DRIVERS
DH Gate Driver On-Resistance
DL Gate Driver On-Resistance
DH Gate Driver Source/
Sink Current
DL Gate Driver Source Current
DL Gate Driver Sink Current
Driver Propagation Delay
DL Transition Time
DH Transition Time
Internal BST Switch On-Resistance
INPUTS AND OUTPUTS
EN Logic-Input Threshold
EN Logic-Input Current
V
EN
I
EN
EN rising edge, hysteresis = 450mV (typ)
EN forced to GND or V
DD
, T
A
= +25°C
High (5V V
DD
)
SKIP
Quad-Level Input Logic
Levels
V
SKIP
Mid (3.3V)
Ref (2.0V)
Low (GND)
SKIP
Logic-Input Current
I
SKIP
SKIP
forced to GND or V
DD
-2
1.20
-0.5
V
CC
-
0.4
3.0
1.7
3.6
2.3
0.4
+2
μA
V
1.7
2.20
+0.5
V
μA
R
BST
R
ON(DH)
R
ON(DL)
I
DH
BST - LX forced to 5V
High state (pullup)
Low state (pulldown)
DH forced to 2.5V, BST - LX forced to 5V
Low state (pulldown)
High state (pullup)
1.2
1.2
1.7
0.9
1.5
1
2.4
10
15
25
35
20
20
20
20
4
7
3.5
3.5
4
2
Ω
Ω
A
A
A
ns
ns
ns
Ω
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
I
DL(SOURCE)
DL forced to 2.5V
I
DL(SINK)
DL forced to 2.5V
DH low to DL high
DL low to DH high
DL falling, C
DL
= 3nF
DL rising, C
DL
= 3nF
DH falling, C
DH
= 3nF
DH rising, C
DH
= 3nF
I
BST
= 10mA, V
DD
= 5V
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 1, V
IN
= 12V, V
DD
= V
CC
= V
EN
= 5V, REFIN = ILIM = REF,
SKIP
= GND. T
A
=
-40°C to +85°C,
unless otherwise
specified.) (Note 1)
PARAMETER
PWM CONTROLLER
Input Voltage Range
Quiescent Supply Current (V
DD
)
On-Time
V
IN
I
DD
+ I
CC
t
ON
FB forced above REFIN
V
IN
= 12V,
V
FB
= 1.0V
(Note 3)
R
TON
= 97.5kΩ (600kHz)
R
TON
= 200kΩ (300kHz)
R
TON
= 302.5kΩ (200kHz)
115
250
348
2
26
1.2
163
306
486
ns
V
mA
SYMBOL
CONDITIONS
MIN
MAX
UNITS
4
_______________________________________________________________________________________
Single Quick-PWM Step-Down
Controller with Dynamic REFIN
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, V
IN
= 12V, V
DD
= V
CC
= V
EN
= 5V, REFIN = ILIM = REF,
SKIP
= GND. T
A
=
-40°C to +85°C,
unless otherwise
specified.) (Note 1)
PARAMETER
Minimum Off-Time
REFIN Voltage Range
FB Voltage Range
SYMBOL
t
OFF(MIN)
V
REFIN
V
FB
(Note 3)
(Note 2)
(Note 2)
V
REFIN
= 0.5V
Measured at FB,
V
IN
= 2V to 26V, V
REFIN
= 1.0V
SKIP
= V
DD
V
REFIN
= 2.0V
V
CC
= 4.5V to 5.5V
With respect to the internal target voltage
(error comparator threshold); rising edge;
hysteresis = 50mV
With respect to the internal target voltage
(error comparator threshold);
falling edge; hysteresis = 50mV
FB forced 25mV below trip threshold
I
SINK
= 3mA
V
UVLO(VCC)
Rising edge, PWM disabled below this level;
hysteresis = 100mV
3.95
0
0
0.49
0.99
1.985
1.985
CONDITIONS
MIN
MAX
350
V
REF
V
REF
0.51
1.01
2.015
2.015
V
V
UNITS
ns
V
V
MAX8792
FB Voltage Accuracy
V
FB
REFERENCE
Reference Voltage
FAULT DETECTION
Output Overvoltage-Protection
Trip Threshold
OVP
250
350
mV
V
REF
Output Undervoltage-Protection
Trip Threshold
Output Undervoltage
Fault-Propagation Delay
PGOOD Output Low Voltage
V
CC
Undervoltage Lockout
Threshold
CURRENT LIMIT
ILIM Input Range
Current-Limit Threshold
Ultrasonic Frequency
GATE DRIVERS
DH Gate Driver On-Resistance
DL Gate Driver On-Resistance
Internal BST Switch On-Resistance
UVP
-240
-160
mV
t
UVP
80
400
0.4
4.45
μs
V
V
0.4
V
ILIMIT
V
ILIM
= 0.4V
ILIM = REF (2.0V)
SKIP
= open (3.3V); V
FB
= V
REFIN
+ 50mV
BST - LX forced Low state (pulldown)
to 5V
High state (pullup)
High state (pullup)
Low state (pulldown)
I
BST
= 10mA, V
DD
= 5V
17
90
17
V
REF
23
110
V
mV
kHz
R
ON(DH)
R
ON(DL)
R
BST
3.5
3.5
4
2
7
Ω
Ω
Ω
_______________________________________________________________________________________
5
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