19-2682; Rev 0; 10/02
Notebook CPU Step-Down Controller
General Description
The MAX1718T step-down controller is intended for core
CPU DC-to-DC converters in notebook computers. It fea-
tures a dynamically adjustable output, 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 relatively
constant switching frequency.
The output voltage can be dynamically adjusted
through the 5-bit digital-to-analog converter (DAC) over
a 0.6V to 1.75V range. The MAX1718T has an internal
multiplexer that accepts three unique 5-bit VID DAC
codes corresponding to performance, battery, and sus-
pend modes. Precision slew-rate control
†
provides
“just-in-time” arrival at the new DAC setting, minimizing
surge currents to and from the battery.
A pair of complementary offset control inputs allows
easy compensation for IR drops in PC board traces or
creation of a voltage-positioned power supply. Voltage
positioning modifies the load-transient response to
reduce output capacitor requirements and total system
power dissipation.
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 MAX1718T is available in a 28-pin QSOP package.
SHUTDOWN
Features
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Quick-PWM Architecture
±1% V
OUT
Accuracy Over Line and Load
5-Bit On-Board DAC with Input Muxes
Precision-Adjustable V
OUT
Slew Control
0.6V to 1.75V Output Adjust Range
Precision Offset Control
Supports Voltage-Positioned Applications
2V to 28V Battery Input Range
Requires a Separate 5V Bias Supply
200kHz/300kHz/550kHz/1000kHz Switching
Frequency
Overvoltage/Undervoltage Protection
Drives Large Synchronous-Rectifier FETs
700µA (typ) I
CC
Supply Current
2µA (typ) Shutdown Supply Current
2V ±1% Reference Output
VGATE Blanking During Transition
Small 28-Pin QSOP Package
MAX1718T
Ordering Information
PART
MAX1718TEEI
TEMP RANGE
-40°C to +85°C
PIN-PACKAGE
28 QSOP
Minimal Operating Circuit
5V INPUT
BATT 2V TO 28V
V
CC
SKP/SDN
ILIM
V
DD
V+
BST
Applications
2-Cell to 4-Cell Li+ Battery to CPU Core Supply
Converters
5V to CPU Core Supply Converters
D0
D1
DUAL MODE™ VID
MUX INPUTS
D2
D3
D4
MAX1718T
DH
LX
DL
GND
OUTPUT
0.6V TO 1.75V
MUX CONTROL
SUSPEND
INPUT
DECODER
ZMODE
SUS
S0
S1
TIME
FB
NEG
POS
VCC
Pin Configuration appears at end of data sheet.
†
Patent pending.
CC
REF
TON
Quick-PWM is a trademark of Maxim Integrated Products, Inc.
VGATE
OVP
POWER-GOOD
OUTPUT
Dual Mode is a trademark of Maxim Integrated Products, Inc.
________________________________________________________________
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.
Notebook CPU Step-Down Controller
MAX1718T
ABSOLUTE MAXIMUM RATINGS
V+ to GND ..............................................................-0.3V to +30V
V
CC
, V
DD
to GND .....................................................-0.3V to +6V
D0–D4, ZMODE, VGATE,
OVP,
SUS to GND ..........-0.3V to +6V
SKP/SDN to GND ...................................................-0.3V to +16V
ILIM, CC, REF, POS, NEG, S1, S0,
TON, TIME to GND .....................................-0.3V to (V
CC
+ 0.3V)
DL to GND ..................................................-0.3V to (V
DD
+ 0.3V)
BST to GND ............................................................-0.3V to +36V
DH to LX .....................................................-0.3V to (BST + 0.3V)
LX to BST..................................................................-6V to +0.3V
REF Short Circuit to GND ...........................................Continuous
Continuous Power Dissipation
28-Pin QSOP (derate 10.8mW/°C above +70°C).........860mW
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
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
= SKP/SDN = 5V, V
OUT
= 1.25V,
T
A
= 0°C to +85°C,
unless otherwise noted.)
PARAMETER
PWM CONTROLLER
Input Voltage Range
Battery voltage, V+
V
CC
, V
DD
V+ = 4.5V to 28V,
includes load
regulation error
DAC codes from 0.9V to 1.75V
DAC codes from 0.6V to 0.875V
2
4.5
-1
-1.5
5
-0.2
0.4
POS - NEG
∆VFB
/ (POS - NEG); POS - NEG = 50mV
150kHz nominal, R
TIME
= 120kΩ
TIME Frequency Accuracy
380kHz nominal, R
TIME
= 47kΩ
38kHz nominal, R
TIME
= 470kΩ
V+ = 5V, FB = 1.2V, TON = GND (1000kHz)
On-Time (Note 1)
TON = REF (550kHz)
V+ = 12V, FB = 1.2V
TON = open (300kHz)
TON = V
CC
(200kHz)
Minimum Off-Time (Note 1)
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+)
SKP/SDN = GND
SKP/SDN = GND
SKP/SDN = GND, V
CC
= V
DD
= 0V or 5V
Measured at V
CC
, FB forced above the regulation point
Measured at V
DD
, FB forced above the regulation point
700
<1
25
2
<1
<1
1200
5
40
5
5
5
µA
µA
µA
µA
µA
µA
TON = V
CC
, open, or REF (200kHz, 300kHz, or 550kHz)
TON = GND (1000kHz)
-80
0.81
-8
-12
-12
230
165
320
465
260
190
355
515
400
300
0.86
+0.2
2.5
+80
0.91
+8
+12
+12
290
215
390
565
500
375
ns
ns
%
28
5.5
+1
%
+1.5
mV
µA
V
mV
V/V
V
CONDITIONS
MIN
TYP
MAX
UNITS
DC Output Voltage Accuracy
Line Regulation Error
Input Bias Current
POS, NEG Common-Mode
Range
POS, NEG Differential Range
POS, NEG Offset Gain
V
CC
= 4.5V to 5.5V, V
BATT
= 4.5V to 28V
FB, POS, NEG
2
_______________________________________________________________________________________
Notebook CPU Step-Down Controller
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, V+ = 15V, V
CC
= V
DD
= SKP/SDN = 5V, V
OUT
= 1.25V,
T
A
= 0°C to +85°C,
unless otherwise noted.)
PARAMETER
Reference Voltage
Reference Load Regulation
REF Sink Current
FAULT PROTECTION
Overvoltage Trip Threshold
Overvoltage Fault Propagation
Delay
Output Undervoltage Fault
Protection Threshold
Output Undervoltage Fault
Propagation Delay
Output Undervoltage Fault
Blanking Time
Current-Limit Threshold Voltage
(Positive, Default)
Current-Limit Threshold Voltage
(Positive, Adjustable)
Current-Limit Threshold Voltage
(Negative)
Current-Limit Threshold Voltage
(Zero Crossing)
Current-Limit Default
Switchover Threshold
Thermal Shutdown Threshold
V
CC
Undervoltage Lockout
Threshold
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-Driver Sink Current
DL Gate-Driver Source Current
BST - LX forced to 5V
DL, high state (pullup)
DL, low state (pulldown)
DH forced to 2.5V, BST - LX forced to 5V
DL forced to 2.5V
DL forced to 2.5V
1.0
1.0
0.4
1.6
4
1.6
3.5
3.5
1.0
Ω
Ω
A
A
A
Hysteresis = +10°C
Rising edge, hysteresis = 20mV, PWM disabled below
this level
Measured at FB with respect to unloaded output voltage
Measured at FB with respect to unloaded output voltage
FB forced 2% outside VGATE trip threshold
I
SINK
= 1mA
High state, forced to 5.5V
4.1
-12
+8
-10
+10
10
0.4
1
Measured at FB
FB forced 2% above trip threshold
With respect to unloaded output voltage
FB forced 2% below trip threshold
From SKP/SDN signal going high, clock speed set by
R
TIME
GND - LX, ILIM = V
CC
GND - LX
LX - GND, ILIM = V
CC
GND - LX
3
T
A
= +25°C to +85°C
T
A
= 0°C to +85°C
ILIM = 0.5V
ILIM = REF (2V)
90
85
35
165
-140
50
200
-117
4
V
CC
- 1 V
CC
- 0.4
150
4.4
-8
+12
65
1.95
2.00
10
70
10
256
100
110
115
65
230
-95
75
2.05
V
µs
%
µs
clks
mV
mV
mV
mV
V
°C
V
%
%
µs
V
µA
I
REF
= 0 to 50µA
REF in regulation
10
CONDITIONS
V
CC
= 4.5V to 5.5V, no REF load
MIN
1.98
TYP
2
MAX
2.02
0.01
UNITS
V
V
µA
MAX1718T
_______________________________________________________________________________________
3
Notebook CPU Step-Down Controller
MAX1718T
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, V+ = 15V, V
CC
= V
DD
= SKP/SDN = 5V, V
OUT
= 1.25V,
T
A
= 0°C to +85°C,
unless otherwise noted.)
PARAMETER
Dead Time
LOGIC AND I/O
Logic Input High Voltage
Logic Input Low Voltage
DAC B-Mode Programming
Resistor, Low
DAC B-Mode Programming
Resistor, High
D0–D4 Pullup/Pulldown
Logic Input Current
D0–D4, ZMODE, SUS,
OVP
D0–D4, ZMODE, SUS,
OVP
D0–D4, 0 to 0.4V or 2.6V to 5.5V applied through resistor,
ZMODE = V
CC
D0–D4, 0 to 0.4V or 2.6V to 5.5V applied through resistor,
ZMODE = V
CC
Entering impedance
mode
D0–D4, ZMODE = GND
ZMODE, SUS,
OVP
For high
Four Level Input Logic Levels
(TON, S0, S1)
SKP/SDN, S0, S1, and TON
Input Current
For open
For REF
For low
SKP/SDN, S0, S1, TON forced to GND or V
CC
SKP/SDN = logic high (SKIP mode)
SKP/SDN Input Levels
SKP/SDN = open (PWM mode)
SKP/SDN = logic low (shutdown mode)
To enable no-fault mode
SKP/SDN Float Level
I
SKP
/SDN = 0µA
12
1.8
-3
2.8
1.4
Pullup
Pulldown
-1
-1
V
CC
- 0.4
3.15
1.65
3.85
2.35
0.5
+3
6.0
2.2
0.5
15
2.2
V
V
µA
V
95
40
8
+1
+1
2.4
0.8
1.05
V
V
kΩ
kΩ
kΩ
µA
DL rising
DH rising
CONDITIONS
MIN
TYP
35
26
MAX
UNITS
ns
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 1, V+ = 15V, V
CC
= V
DD
= SKP/SDN = 5V, V
OUT
= 1.25V,
T
A
= -40°C to +85°C,
unless otherwise noted.) (Note 2)
PARAMETER
PWM CONTROLLER
DC Output Voltage Accuracy
V+ = 4.5V to 28V,
includes load
regulation error
DAC codes from 0.9V to 1.75V
DAC codes from 0.6V to 0.875V
-1.5
-2.0
-8
-12
-12
230
165
320
465
+1.5
%
+2.0
+8
+12
+12
290
215
390
565
ns
%
CONDITIONS
MIN
TYP
MAX
UNITS
150kHz nominal, R
TIME
= 120kΩ
TIME Frequency Accuracy
380kHz nominal, R
TIME
= 47kΩ
38kHz nominal, R
TIME
= 470kΩ
V+ = 5V, FB = 1.2V, TON = GND (1000kHz)
On-Time (Note 1)
TON = REF (550kHz)
V+ = 12V, FB = 1.2V
TON = open (300kHz)
TON = V
CC
(200kHz)
4
_______________________________________________________________________________________
Notebook CPU Step-Down Controller
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, V+ = 15V, V
CC
= V
DD
= SKP/SDN = 5V, V
OUT
= 1.25V,
T
A
= -40°C to +85°C,
unless otherwise noted.) (Note 2)
PARAMETER
Minimum Off-Time (Note 1)
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 PROTECTION
Overvoltage Trip Threshold
Output Undervoltage Protection
Threshold
Current-Limit Threshold Voltage
(Positive, Default)
Current-Limit Threshold Voltage
(Positive, Adjustable)
Current-Limit Threshold Voltage
(Negative)
V
CC
Undervoltage Lockout
Threshold
VGATE Lower Trip Threshold
VGATE Upper Trip Threshold
GATE DRIVERS
DH Gate-Driver On-Resistance
DL Gate-Driver On-Resistance
LOGIC AND I/O
Logic Input High Voltage
Logic Input Low Voltage
D0–D4, ZMODE, SUS,
OVP
D0–D4, ZMODE, SUS,
OVP
2.4
0.8
V
V
BST - LX forced to 5V
DL, high state (pullup)
DL, low state (pulldown)
3.5
3.5
1.0
Ω
Ω
Measured at FB
With respect to unloaded output voltage
GND - LX, ILIM = V
CC
GND - LX
LX - GND, ILIM = V
CC
Rising edge, hysteresis = 20mV, PWM disabled below
this level
Measured at FB with respect to unloaded output voltage
Measured at FB with respect to unloaded output voltage
ILIM = 0.5V
ILIM = REF (2V)
1.95
65
80
33
160
-145
4.1
-12.5
+7.5
2.05
75
115
65
240
-90
4.4
-7.5
+12.5
V
%
mV
mV
mV
V
%
%
SKP/SDN = 0
SKP/SDN = 0
SKP/SDN = 0, V
CC
= V
DD
= 0 or 5V
V
CC
= 4.5V to 5.5V, no REF load
1.98
Measured at V
CC
, FB forced above the regulation point
Measured at V
DD
, FB forced above the regulation point
1300
5
40
5
5
5
2.02
µA
µA
µA
µA
µA
µA
V
CONDITIONS
TON = V
CC
, open, or REF (200kHz, 300kHz, or 550kHz)
TON = GND (1000kHz)
MIN
TYP
MAX
500
375
UNITS
ns
MAX1718T
_______________________________________________________________________________________
5
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