19-1758; Rev 0; 8/00
High-Speed, Adjustable, Synchronous Step-Down
Controllers with Integrated Voltage Positioning
General Description
The MAX1716/MAX1854/MAX1855 step-down con-
trollers are intended for core CPU DC-DC converters in
notebook computers. They feature a dynamically
adjustable output (5-bit DAC), ultra-fast transient
response, high DC accuracy, and high efficiency need-
ed for leading-edge CPU core power supplies. Maxim's
proprietary Quick-PWM™ quick-response, constant-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 relative-
ly constant switching frequency.
The MAX1716/MAX1854/MAX1855 are designed
specifically for CPU core applications requiring a volt-
age-positioned supply. The voltage-positioning input
(VPS), combined with a high DC accuracy control loop,
is used to implement a power supply that modifies its
output set point in response to the load current. This
arrangement decreases full-load power dissipation and
reduces the required number of output capacitors.
The 28V input range of the MAX1716/MAX1854/MAX1855
enables single-stage buck conversion from high-volt-
age batteries for the maximum possible efficiency.
Alternatively, the devices’ high-frequency capability
combined with two-stage conversion (stepping down
the +5V system supply instead of the battery) allows
the smallest possible physical size. The output voltage
can be dynamically adjusted through the 5-bit digital-
to-analog converter (DAC) inputs.
The MAX1716/MAX1854/MAX1855 are available in a
24-pin QSOP package. For applications requiring
SpeedStep™ power control (see the MAX1717).
o
High-Efficiency Voltage Positioning
o
Quick-PWM Architecture
o
±1% V
OUT
Line-Regulation Accuracy
o
Adjustable Output Range (5-Bit DAC)
MAX1716: 0.925V to 1.6V
MAX1854: 0.925V to 2.0V
MAX1855: 0.600V to 1.75V
o
2V to 28V Input Range
o
200/300/400/550kHz Switching Frequency
o
Output Undervoltage Protection
o
Overvoltage Protection (MAX1716/MAX1855)
o
Drive Large Synchronous-Rectifier MOSFETs
o
1.7ms Digital Soft-Start
o
700µA I
CC
Supply Current
o
1µA Shutdown Supply Current
o
2V ±1% Reference Output
o
V
GATE
Transition-Complete Indicator
o
Small 24-Pin QSOP Package
Features
MAX1716/MAX1854/MAX1855
Typical Operating Circuit
+5V INPUT
V
CC
SHDN
ILIM
REF
CC
V
DD
V+
BST
DH
OUTPUT
BATTERY
2V TO 28V
________________________Applications
Notebook Computers
Docking Stations
CPU Core Supply
Single-Stage (BATT to V
CORE
) Converters
Two-Stage (+5V to V
CORE
) Converters
MAX1716
MAX1854
LX
SKIP
MAX1855
DL
GND
CS
VPS
Ordering Information
PART
MAX1716EEG
MAX1854EEG
MAX1855EEG
TEMP. RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
24 QSOP
24 QSOP
24 QSOP
DAC
INPUTS
TON
D0
D1
D2
D3
D4
PGND
FB
VGATE
Quick-PWM is a trademark of Maxim Integrated Products.
SpeedStep is a trademark of Intel Corp.
Pin Configuration appears at end of data sheet.
1
________________________________________________________________
Maxim Integrated Products
For free samples and the latest literature, visit www.maxim-ic.com or phone 1-800-998-8800.
For small orders, phone 1-800-835-8769.
High-Speed, Adjustable, Synchronous Step-Down
Controllers with Integrated Voltage Positioning
MAX1716/MAX1854/MAX1855
ABSOLUTE MAXIMUM RATINGS
V+ to GND ..............................................................-0.3V to +30V
V
CC
, V
DD
to GND .....................................................-0.3V to +6V
PGND to GND.....................................................................±0.3V
SHDN,
VGATE to GND .............................................-0.3V to +6V
ILIM, FB, CC, REF, D0–D4, VPS,
TON to GND ...........................................-0.3V to (V
CC
+ 0.3V)
SKIP
to GND (Note 1).................................-0.3V to (V
CC
+ 0.3V)
DL to PGND................................................-0.3V to (V
DD
+ 0.3V)
BST to GND ............................................................-0.3V to +36V
DH to LX ....................................................-0.3V to (V
BST
+ 0.3V)
LX to BST..................................................................-6V to +0.3V
CS to GND.................................................................-2V to +30V
REF Short Circuit to GND ...........................................Continuous
Continuous Power Dissipation (T
A
= +70°C)
24-Pin QSOP (derate 9.5mW/°C above +70°C)...........762mW
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
Note 1:
SKIP
may be forced below -0.3V, temporarily exceeding the absolute maximum rating, for the purpose of debugging proto-
type breadboards, using the no-fault test mode. Limit the current drawn to -2mA (max).
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, V
CC
= V
DD
= 5V,
SKIP
= V
CC
, VPS = PGND,
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
1.35V to 2.0V
DC Output Voltage Accuracy
(Notes 2, 3)
V+ = 4.5V to 28V,
VPS = PGND
DAC codes from
0.925V to 1.3V
DAC codes from
0.6V to 0.9V
FB Input Bias Current
VPS Input Bias Current
VPS Gain
CS Input Bias Current
ILIM Input Leakage Current
Soft-Start Ramp Time
I
FB
I
VPS
A
VPS
I
CS
I
ILIM
FB = 0.6V to 2.0V
V
VPS
=
±40mV
V
VPS
= 0 or -40mV, gain from VPS to FB
0 to 28V
V
ILIM
= 0 or 5.0V
0 to full ILIM
TON = GND
On-Time (Note 4)
t
ON
V+ = 11.0V,
V
FB
= 1.5V
TON = REF
TON = open
TON = V
CC
Minimum Off-Time (Note 4)
t
OFF(MIN)
205
280
425
615
2
4.5
-1
-1.2
-1.5
-0.2
-1
0.153
-1
0.01
1.7
255
327
470
678
400
300
375
520
740
500
ns
ns
0.175
28
5.5
1
1.2
1.5
0.2
1
0.197
1
100
µA
µA
%/mV
µA
nA
ms
%
V
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
2
_______________________________________________________________________________________
High-Speed, Adjustable, Synchronous Step-Down
Controllers with Integrated Voltage Positioning
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, V+ = +15V, V
CC
= V
DD
= 5V,
SKIP
= V
CC
, VPS = PGND,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical
values are at T
A
= +25°C.)
PARAMETER
BIAS AND REFERENCE
Quiescent Supply Current (V
CC
)
Quiescent Supply Current (V
DD
)
Quiescent Supply Current (V+)
Shutdown Supply Current (V
CC
)
Shutdown Supply Current (V
DD
)
Shutdown Supply Current (V+)
Reference Voltage
Reference Load Regulation
REF Sink Current
REF Fault Lockout Voltage
FAULT PROTECTION
Output Overvoltage Fault
Threshold (Note 5)
Output Overvoltage Fault
Propagation Delay (Note 5)
Output Undervoltage Fault
Threshold (Foldback)
Output Undervoltage Fault
Propagation Delay
Output Undervoltage Fault
Blanking Time (Foldback)
Current-Limit Threshold
(Positive, Default)
Current-Limit Threshold
(Positive, Adjustable)
Negative Current-Limit
Threshold
Zero-Crossing Current-Limit
Threshold
Thermal Shutdown Threshold
V
CC
Undervoltage Lockout
Threshold
V
ITH
V
ITH
FB forced to 2% below trip threshold
From
SHDN
signal going high
V
PGND
- V
CS
, ILIM = V
CC
V
PGND
- V
CS
V
PGND
- V
CS
V
PGND
- V
CS
Hysteresis = 10°C
Rising edge, hysteresis = 20mV, switching
disabled below this level
4.0
V
ILIM
= 0.5V
V
ILIM
= 2V (REF)
10
110
40
170
120
50
200
-1.2
×
V
ITH
3
150
4.45
Measured at FB
MAX1716
MAX1855
1.8
1.97
1.9
2.0
1.5
35
40
10
30
130
60
230
45
2.0
2.03
V
µs
%
µs
ms
mV
mV
mV
mV
°C
V
I
REF
V
REF
I
CC
I
DD
I+
SHDN
= GND
SHDN
= GND
SHDN
= GND, V
CC
= V
DD
= 0 or 5V
V
CC
= 4.5V to 5.5V, no external REF load
I
REF
= 0 to 50µA
REF in regulation
Falling edge
10
1.6
1.98
Measured at V
CC
, FB forced above the
regulation point
Measured at V
DD
, FB forced above the
regulation point
700
<1
25
<1
<1
<1
2
950
5
40
5
5
5
2.02
0.01
µA
µA
µA
µA
µA
µA
V
V
µA
V
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
MAX1716/MAX1854/MAX1855
FB forced to 2% above trip threshold
(MAX1716/MAX1855 only)
_______________________________________________________________________________________
3
High-Speed, Adjustable, Synchronous Step-Down
Controllers with Integrated Voltage Positioning
MAX1716/MAX1854/MAX1855
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, V+ = +15V, V
CC
= V
DD
= 5V,
SKIP
= V
CC
, VPS = PGND,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical
values are at T
A
= +25°C.)
PARAMETER
VGATE Lower Trip Threshold
VGATE Upper Trip Threshold
VGATE Propagation Delay
VGATE Output Low Voltage
VGATE Leakage Current
GATE DRIVERS
DH Gate Driver On-Resistance
DL Gate Driver On-Resistance
DH Gate Driver Source/Sink
Current
DL Gate Drive Sink Current
DL Gate Driver Source Current
Dead-Time
LOGIC AND I/O
Logic Input High Voltage
Logic Input Low Voltage
V
IH
V
IL
D0−D4,
SHDN, SKIP
D0−D4,
SHDN, SKIP
TON = V
CC
(200kHz operation)
TON Input Levels
TON = open (300kHz operation)
TON = REF (400kHz operation)
TON = GND (550kHz operation)
Logic Input Current
D0−D4 Pullup Current
SKIP
No-Fault Mode Current
TON = GND or V
CC
SHDN, SKIP
= GND or V
CC
D0−D4 = GND
T
A
= +25°C
-3
-1
3
-1.5
5
V
CC
- 0.4
3.15
1.65
3.85
2.35
0.5
3
1
10
-0.1
µA
µA
mA
V
2.4
0.8
V
V
R
ON(DH)
R
ON(DL)
I
DH
I
DL
I
DL
V
BST
- V
LX
forced to 5V
High state (pullup)
Low state (pulldown)
DH forced to 2.5V, V
BST
- V
LX
forced to 5V
DL forced to 5V
DL forced to 2.5V
DL rising
DH rising
1.3
1.5
0.5
1
3
1
35
26
5
5
1.7
Ω
Ω
A
A
A
ns
SYMBOL
CONDITIONS
Measured at FB with respect to unloaded
output voltage, falling edge
Measured at FB with respect to unloaded
output voltage, rising edge
Falling edge, FB forced 2% below or above
VGATE trip threshold
I
SINK
= 1mA
High state, forced to 5.5V
MIN
-12.5
7.5
TYP
-10
10
1.5
0.4
1
MAX
-7.5
12.5
UNITS
%
%
µs
V
µA
4
_______________________________________________________________________________________
High-Speed, Adjustable, Synchronous Step-Down
Controllers with Integrated Voltage Positioning
MAX1716/MAX1854/MAX1855
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 1, V+ = +15V, V
CC
= V
DD
= 5V,
SKIP
= V
CC
, VPS = PGND,
T
A
= -40°C to +85°C,
unless otherwise noted.) (Note 6)
PARAMETER
PWM CONTROLLER
Input Voltage Range
Battery voltage, V+
V
CC
, V
DD
V+ = 4.5V to 28V,
VPS = PGND
I
FB
I
VPS
A
VPS
I
CS
I
ILIM
FB = 0.6V to 2.0V
V
VPS
=
±40mV
V
VPS
= 0 or -40mV, gain from VPS to FB
0 to 28V
V
ILIM
= 0 or 5.0V
TON = GND
On-Time (Note 4)
t
ON
V+ = 11.0V,
V
FB
= 1.5V
TON = REF
TON = open
TON = V
CC
Minimum Off-Time (Note 4)
BIAS AND REFERENCE
Quiescent Supply Current (V
CC
)
Quiescent Supply Current (V
DD
)
Quiescent Supply Current (V+)
Shutdown Supply Current (V
CC
)
Shutdown Supply Current (V
DD
)
Shutdown Supply Current (V+)
Reference Voltage
Reference Load Regulation
REF Sink Current
FAULT PROTECTION
Output Overvoltage Fault
Threshold (Note 5)
Output Undervoltage Fault
Threshold (Foldback)
Output Undervoltage Fault
Blanking Time (Foldback)
From
SHDN
signal going high
Measured at FB
MAX1716
MAX1855
1.8
1.97
35
10
2.0
2.03
45
30
%
ms
V
I
REF
V
REF
I
CC
I
DD
I+
SHDN
= GND
SHDN
= GND
SHDN
= GND, V+ = 28V, V
CC
= V
DD
= 0 or 5V
V
CC
= 4.5V to 5.5V, no external REF load
I
REF
= 0 to 50µA
REF in regulation
10
1.98
Measured at V
CC
, FB forced above the
regulation point
Measured at V
DD
, FB forced above the
regulation point
950
5
40
5
5
5
2.02
0.01
µA
µA
µA
µA
µA
µA
V
V
µA
t
OFF(MIN)
205
280
425
615
DAC codes from
1.35V to 2.0V
DAC codes from
0.6V to 1.3V
2
4.5
-1.6
-2
-0.2
-1
0.153
-1
28
5.5
1.6
%
2
0.2
1
0.197
1
100
300
375
520
740
500
ns
ns
µA
µA
%/mV
µA
nA
V
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
DC Output Voltage Accuracy
(Notes 2, 3)
FB Input Bias Current
VPS Input Bias Current
VPS Gain
CS Input Bias Current
ILIM Input Leakage Current
_______________________________________________________________________________________
5
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