19-3319; Rev 2; 9/05
KIT
ATION
EVALU
BLE
AVAILA
Dynamically Adjustable 6-Bit VID
Step-Down Controller
Features
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Quick-PWM Architecture
±1% V
OUT
Accuracy Over Line and Load
6-Bit On-Board DAC with Input Muxes
Precision-Adjustable V
OUT
Slew Control
0.275V to 1.850V Output Adjust Range
Remote Feedback and Ground Sense
Supports Voltage-Positioned Applications
2V to 28V Battery Input Range
200kHz/300kHz/550kHz/1000kHz Switching
Frequency
Over/Undervoltage Protection
Drives Large Synchronous-Rectifier FETs
800µA (typ) I
CC
Supply Current
10µA (typ) Shutdown Supply Current
2V ±0.75% Reference Output
PGOOD Blanking During Transition
General Description
The MAX8720 step-down controller is intended for core
CPU DC-DC converters in notebook computers. It fea-
tures a dynamically adjustable output, ultra-fast transient
response, high DC accuracy, and the high efficiency
needed for leading-edge CPU core power supplies.
Maxim’s proprietary Quick-PWM™ quick-response, con-
stant-on-time, PWM control scheme handles wide
input/output voltage ratios with ease and provides
100ns “instant-on” response to load transients while
maintaining a relatively constant switching frequency.
The output voltage can be dynamically adjusted through
the 6-bit digital-to-analog converter (DAC) over a 0.275V
to 1.850V range in 25mV steps. The MAX8720 has inde-
pendent four-level logic inputs for setting the suspend
voltage (S0-S1). Precision slew-rate control provides
“just-in-time” arrival at the new DAC setting, minimizing
surge currents to and from the battery. The internal DAC
of the MAX8720 is synchronized to the slew-rate clock
for improved operation under aggressive power man-
agement of newer chipsets and operating systems that
can make incomplete mode transitions. Remote feed-
back and ground-sense inputs allow easy compensa-
tion for IR drops in PC board traces.
Single-stage buck conversion allows these devices to
directly step down high-voltage batteries for the highest
possible efficiency. Alternatively, two-stage conversion
(stepping down the 5V system supply instead of the
battery) at a higher switching frequency allows the mini-
mum possible physical size.
The MAX8720 is available in a 28-pin QSOP or 36-pin
6mm x 6mm thin QFN package.
MAX8720
Ordering Information
PART
MAX8720EEI
MAX8720ETX
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
28 QSOP
36 Thin QFN 6mm x 6mm
Minimal Operating Circuit
+5V BIAS
V
CC
SHDN
V
DD
V+
BST
DH
OUTPUT (V
OUT
)
0.275V TO 1.850V
INPUT (V
IN
)
7V TO 28V
Applications
CPU Core Supply Converters
GPU Core Supply Converters
Notebook and Subnotebook Computers
ILIM
AGND
SKIP
SUS
LX
MAX8720
DL
PGOOD
VID0
VID1
VID2
VID3
VID4
D0
D1
D2
D3
D4
D5
S0
PGND
FB
FBS
GNDS
CC
REF
TIME
S1
Quick-PWM is a trademark of Maxim Integrated Products, Inc.
Pin Configurations appear at end of data sheet.
VID5
________________________________________________________________
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.
Dynamically Adjustable 6-Bit VID
Step-Down Controller
MAX8720
ABSOLUTE MAXIMUM RATINGS
(Note 1)
V
CC
to AGND............................................................-0.3V to +6V
V
DD
to PGND............................................................-0.3V to +6V
AGND to PGND .....................................................-0.3V to +0.3V
V+ to PGND............................................................-0.3V to +30V
SHDN
to AGND ......................................................-0.3V to +16V
D0–D5, PGOOD, SUS,
SKIP
to AGND .....................-0.3V to +6V
FB, FBS, GNDS to AGND ...........................-0.3V to (V
CC
+ 0.3V)
CC, ILIM, REF, TIME to AGND ...................-0.3V to (V
CC
+ 0.3V)
S0, S1, TON to AGND ................................-0.3V to (V
CC
+ 0.3V)
BST to PGND..........................................................-0.3V to +36V
LX to BST..................................................................-6V to +0.3V
DH to LX .....................................................-0.3V to (BST + 0.3V)
DL to PGND................................................-0.3V to (V
DD
+ 0.3V)
REF Short Circuit to AGND.........................................Continuous
Continuous Power Dissipation (T
A
= +70°C)
28-Pin QSOP (derate 10.8mW/°C above +70°C)........860mW
36-Pin TQFN (derate 26.3mW/°C above +70°C) .....2105mW
Operating Temperature
Extended Temperature Range .......................-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +165°C
Lead Temperature (soldering, 10s) .................................+300°C
Note 1:
For the MAX8720EEI, AGND and PGND refer to a single pin designated GND.
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+ = 15V,
SHDN
=
SKIP
= V
DD
= V
CC
= +5V, V
OUT
= 1.25V,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical
values are at T
A
= +25°C.)
PARAMETER
PWM CONTROLLER
Input Voltage Range
Battery voltage, V+
V
CC
, V
DD
DAC codes from
0.9V to 1.85V
DC Output Voltage Accuracy
V+ = 4.5V to 28V,
includes load
regulation error
DAC codes from
0.45V to 0.875V
DAC codes from
0.275V to 0.425V
Line Regulation Error
Remote-Sense Voltage Error
FBS Input Bias Current
GNDS Input Bias Current
FB Input Resistance
150kHz, R
TIME
= 120kΩ
TIME Frequency Accuracy
818kHz, R
TIME
= 22kΩ
38kHz, R
TIME
= 470kΩ
V+ = 5V, FB = 1.25V, TON = GND
(1000kHz)
TON = REF
(550kHz)
On-Time (Note 2)
t
ON
V+ = 12V,
FB = 1.25V
TON = open
(300kHz)
TON = V
CC
(200kHz)
V
CC
= 4.5V to 5.5V, V+ = 4.5V to 28V
FB to FBS or AGND to GNDS = 0 to 25mV
FB, FBS
GNDS
-0.2
-1
115
-8
-12
-12
230
165
320
465
260
190
355
515
180
2
4.5
-1
-10
-18
5
3
+0.2
+1
265
+8
+12
+12
290
215
ns
390
565
%
28
5.5
+1
+10
mV
+18
mV
mV
µA
µA
kΩ
V
%
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
2
_______________________________________________________________________________________
Dynamically Adjustable 6-Bit VID
Step-Down Controller
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, V+ = 15V,
SHDN
=
SKIP
= V
DD
= V
CC
= +5V, V
OUT
= 1.25V,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical
values are at T
A
= +25°C.)
PARAMETER
Minimum Off-Time (Note 2)
BIAS AND REFERENCE
Quiescent Supply Current (V
CC
)
Quiescent Supply Current (V
DD
)
Quiescent Battery Supply
Current (V+)
Shutdown Supply Current (V
CC
)
Shutdown Supply Current (V
DD
)
Shutdown Battery Supply
Current (V+)
Reference Voltage
Reference Load Regulation
REF Sink Current
FAULT DETECTION
V
CC
Undervoltage-Lockout
Threshold
Output Overvoltage Trip
Threshold
Output Overvoltage Fault-
Propagation Delay
Output Undervoltage-Protection
Trip Threshold
Output Undervoltage Fault-
Propagation Delay
PGOOD Transition Blanking Time
PGOOD Lower Trip Threshold
PGOOD Upper Trip Threshold
PGOOD Propagation Delay
PGOOD Output Low Voltage
PGOOD Leakage Current
Thermal-Shutdown Threshold
CURRENT LIMIT
ILIM Adjustment Range
0.5
V
REF
V
I
PGOOD
T
SHDN
t
PGOOD
t
UVP
t
OVP
FB forced 2% above regulation
With respect to unloaded output voltage
FB forced 2% below trip threshold
After X = Y, clock speed set by R
TIME
Measured at FB with respect to unloaded
output voltage, hysteresis = 1%
Measured at FB with respect to unloaded
output voltage, hysteresis = 1%
Falling edge, 50mV overdrive
I
SINK
= 4mA
High state, PGOOD forced to 5.5V
Hysteresis = 10°C
+150
-17
+13
65
Rising edge, hysteresis = 20mV, PWM
disabled below this level
4.1
2.20
2.25
10
70
10
8
-15
+15
10
0.4
1
-13
+17
75
4.4
2.30
V
V
µs
%
µs
clk
%
%
µs
V
µA
°C
I
CC
I
DD
I
+
I
CC
I
DD
I
+
V
REF
∆V
REF
SHDN
= GND
SHDN
= GND
SHDN
= GND, V
CC
= V
DD
= 0V or 5V
V
CC
= 4.5V to 5.5V,
I
REF
= 0
I
REF
= 0 to 50µA
REF in regulation
10
T
A
= +25°C to +85°C
T
A
= 0°C to +85°C
1.985
1.98
FB forced above their regulation points
FB forced above their regulation points
700
<1
25
10
<1
<1
2.00
2.00
1200
5
40
25
5
5
2.015
2.02
0.01
µA
µA
µA
µA
µA
µA
V
V
µA
SYMBOL
t
OFF(MIN)
CONDITIONS
TON = V
CC
, open, or REF (200kHz, 300kHz,
or 550kHz)
TON = GND (1000kHz)
MIN
TYP
400
300
MAX
500
375
UNITS
ns
MAX8720
_______________________________________________________________________________________
3
Dynamically Adjustable 6-Bit VID
Step-Down Controller
MAX8720
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, V+ = 15V,
SHDN
=
SKIP
= V
DD
= V
CC
= +5V, V
OUT
= 1.25V,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical
values are at T
A
= +25°C.)
PARAMETER
Current-Limit Threshold (Fixed)
Current-Limit Threshold
(Adjustable)
Current-Limit Threshold
(Negative)
Current-Limit Threshold (Zero
Crossing)
Current-Limit Default
Switchover Threshold
ILIM Leakage Current
GATE DRIVERS
DH Gate-Driver On-Resistance
(Note 3)
DL Gate-Driver On-Resistance
(Note 3)
DH Gate-Driver Source/Sink
Current
DL Gate-Driver Source Current
DL Gate-Driver Sink Current
Dead Time
INPUTS AND OUTPUTS
Logic high
SHDN
Input Level
Logic Input High Voltage
Logic Input Low Voltage
Logic Input Current
V
SHDN
V
IH
V
IL
Logic low
No-fault mode
D0–D5,
SKIP,
SUS
D0–D5,
SKIP,
SUS
D0–D5,
SKIP,
SUS
High
Four-Level Input Logic
TON, S0, S1
Open
REF
GND
Input Leakage Current
SHDN,
TON, S0, S1 forced to V
CC
or GND
-3
-1
V
CC
-
0.2
3.15
1.65
3.85
2.35
0.5
+3
µA
V
12
2.4
0.8
+1
2.4
0.4
15
V
V
µA
V
R
DH
BST-LX forced to 5V
DL, high state
DL, low state
I
DH
I
DL
(SOURCE)
SYMBOL
V
LIMIT
V
LIMIT
V
PGND
- V
LX
,
ILIM = V
CC
V
PGND
- V
LX
CONDITIONS
T
A
= +25°C to +85°C
T
A
= 0°C to +85°C
V
ILIM
= 2.00V
V
ILIM
= 0.50V
MIN
90
85
165
35
-140
TYP
100
200
50
-117
-117
4
MAX
110
115
230
65
-90
UNITS
mV
mV
mV
%
mV
V
LX
- V
PGND
,
SKIP
= ILIM = V
CC
,
V
NEG
V
LX
- V
PGND
,
SKIP
= V
CC
, adjustable mode,
percent of current limit
V
PGND
- V
LX
,
SKIP
= GND
V
ZX
3
V
CC
-
1
V
CC
-
0.4
0.1
V
µA
QSOP package
TQFN package
QSOP package
TQFN package
1.0
1.0
1.0
1.0
0.4
2
1.6
4
35
26
3.5
4.5
3.5
4.0
1.0
Ω
R
DL
Ω
DH forced to 2.5V, BST-LX forced to 5V
DL forced to 2.5V
DL forced to 2.5V
DL rising
DH rising
A
A
A
ns
I
DL (SINK)
t
DEAD
4
_______________________________________________________________________________________
Dynamically Adjustable 6-Bit VID
Step-Down Controller
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 1, V+ =15V,
SHDN
=
SKIP
= V
DD
= V
CC
= +5V, V
OUT
= 1.25V,
T
A
= -40°C to +85°C,
unless otherwise noted.
Typical values are at T
A
= +25°C.) (Note 4)
PARAMETER
PWM CONTROLLER
Input Voltage Range
Battery Voltage, V+
V
CC
, V
DD
DAC codes from 0.9V
to 1.85V
DC Output Voltage Accuracy
V+ = 4.5V to 28V,
includes load
regulation error
DAC codes from
0.45V to 0.875V
DAC codes from
0.275V to 0.425V
FB Input Resistance
150kHz, R
TIME
= 120kΩ
TIME Frequency Accuracy
818kHz, R
TIME
= 22kΩ
38kHz, R
TIME
= 470kΩ
V+ = 5V, FB = 1.25V, TON = GND
(1000kHz)
TON = REF
(550kHz)
On-Time (Note 2)
t
ON
V+ = 12V,
FB = 1.25V
TON = open
(300kHz)
TON = V
CC
(200kHz)
Minimum Off-Time (Note 2)
BIAS AND REFERENCE
Quiescent Supply Current (V
CC
)
Quiescent Supply Current (V
DD
)
Quiescent Battery Supply
Current (V+)
Shutdown Supply Current (V
CC
)
Shutdown Supply Current (V
DD
)
Shutdown Battery Supply
Current (V+)
Reference Voltage
FAULT DETECTION
V
CC
Undervoltage-Lockout
Threshold
Rising edge, hysteresis = 20mV, PWM
disabled below this level
4.1
4.4
V
I
CC
I
DD
I
+
I
CC
I
DD
I
+
V
REF
SHDN
= GND
SHDN
= GND
SHDN
= GND, V
CC
= V
DD
= 0V or 5V
V
CC
= 4.5V to 5.5V, no REF load
1.98
FB forced above their regulation points
FB forced above their regulation points
1300
5
40
25
5
5
2.02
µA
µA
µA
µA
µA
µA
V
t
OFF(MIN)
TON = V
CC
, open, or REF (200kHz, 300kHz,
or 550kHz)
TON = GND (1000kHz)
2
4.5
-1
-15
-18
115
-8
-12
-12
230
165
320
465
28
5.5
+1
+15
mV
+18
265
+8
+12
+12
290
215
ns
390
565
500
375
%
kΩ
V
%
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
MAX8720
ns
_______________________________________________________________________________________
5
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