MAX8743.pdf

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19-3318; Rev 0; 6/04
Dual, High-Efficiency, Step-Down
Controller with High Impedance in Shutdown
General Description
The MAX8743 is a dual pulse-width modulation (PWM)
controller configured for step-down (buck) topologies
that provides the high efficiency, excellent transient
response, and high DC output accuracy necessary for
stepping down high-voltage batteries to generate low-
voltage chipset and RAM power supplies in notebook
computers. The CS_ inputs can be used with low-side
sense resistors to provide accurate current limits or can
be connected to LX_, using low-side MOSFETs as cur-
rent-sense elements. High output impedance in shut-
down eliminates negative output voltages, saving the
cost of a Schottky diode at the output.
The on-demand PWM controllers are free running, con-
stant on-time with input feed-forward. This configuration
provides ultra-fast transient response, wide input-output
differential range, low supply current, and tight load-reg-
ulation characteristics. The MAX8743 is simple and easy
to compensate.
Single-stage buck conversion allows the MAX8743 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 bat-
tery at a higher switching frequency) allows the minimum
possible physical size.
The MAX8743 is intended for generating chipset, DRAM,
CPU I/O, or other low-voltage supplies down to 1V. The
MAX8743 is available in 28-pin QSOP and 36-pin thin
QFN packages.
Features
♦
Ultra-High Efficiency
♦
Accurate Current-Limit Option
♦
Quick-PWM™ with 100ns Load-Step Response
♦
1% V OUT Accuracy over Line and Load
♦
High Output Impedance in Shutdown
♦
Dual Mode™ Fixed 1.8V/1.5V/Adj or 2.5V/Adj Outputs
♦
Adjustable 1V to 5.5V Output Range
♦
2V to 28V Battery Input Range
♦
200kHz/300kHz/420kHz/540kHz Nominal Switching
Frequency
♦
Adjustable Overvoltage Protection
♦
1.7ms Digital Soft-Start
♦
Drives Large Synchronous-Rectifier FETs
♦
Power-Good Window Comparator
♦
2V ±1% Reference Output
Ordering Information
PART
TEMP RANGE
PIN-PACKAGE
MAX8743EEI
-40°C to +85°C
28 QSOP
MAX8743ETX
-40°C to +85°C
36 Thin QFN
6mm x 6mm
Minimal Operating Circuit
Applications
Notebook Computers
CPU Core Supplies
Chipset/RAM Supplies as Low as 1V
1.8V and 2.5V I/O Supplies
5V INPUT
BATTERY
4.5V TO 28V
V DD
V+
V CC
UVP
OVP
MAX8743EEI
ILIM1
ILIM2
ON1
ON2
BST1
BST2
OUTPUT1
1.8V
DH1
DH2
OUTPUT2
2.5V
LX1
LX2
DL1
TON
DL2
CS2
CS1
OUT1
PGOOD
OUT2
REF
SKIP
Pin Configurations appear at end of data sheet.
Quick-PWM and Dual Mode are trademarks of Maxim Integrated
Products, Inc.
FB1
FB2
GND
________________________________________________________________ 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.
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Dual, High-Efficiency, Step-Down
Controller with High Impedance in Shutdown
ABSOLUTE MAXIMUM RATINGS (Note 1)
V+ to AGND..............................................................-0.3 to +30V
V CC to AGND............................................................-0.3V to +6V
V DD to PGND............................................................-0.3V to +6V
AGND to PGND .....................................................-0.3V to +0.3V
PGOOD, OUT_ to AGND..........................................-0.3V to +6V
OVP, UVP, ILIM_, FB_, REF,
SKIP, TON, ON_ to AGND......................-0.3V to (V CC + 0.3V)
DL_ to PGND ..............................................-0.3V to (V DD + 0.3V)
BST_ to AGND........................................................-0.3V to +36V
CS_ to AGND.............................................................-6V to +30V
DH1 to LX1 ..............................................-0.3V to (V BST1 + 0.3V)
LX_ to BST_ ..............................................................-6V to +0.3V
DH2 to LX2 ..............................................-0.3V to (V BST2 + 0.3V)
REF Short Circuit to GND ...........................................Continuous
Continuous Power Dissipation (T A = +70°C)
28-Pin QSOP (derate 10.8mW/°C above +70°C)........860mW
36-Pin 6mm ✕ 6mm Thin QFN
(derate 26.3mW/°C above +70°C) .............................2105mW
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: For the MAX8743EEI, 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 DD = V CC = 5V, SKIP = AGND, V+ = 15V, T A = 0°C to +85°C , typical values are at +25°C, unless otherwise
noted.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX UNITS
PWM CONTROLLERS
Input Voltage Range
V+
Battery voltage, V+
2
28
V
V CC /V DD V CC , V DD
4.5
5.5
V+ = 2V to 28V, I LOAD
= 0 to 8A, SKIP = V CC ,
+25°C to +85°C
FB1 to AGND
1.782
1.8
1.818
FB1 to V CC
1.485
1.5
1.515
DC Output Voltage OUT1
(Note 2)
V OUT1
FB1 to OUT1
0.99
1
1.01
V
V+ = 2V to 28V, I LOAD
= 0 to 8A, SKIP = V CC ,
0°C to +85°C
FB1 to AGND
1.773
1.8
1.827
FB1 to V CC
1.477
1.5
1.523
FB1 to OUT1
0.985
1
1.015
V+ = 4.5V to 28V,
I LOAD = 0 to 4A,
SKIP = V CC ,
+25°C to +85°C
FB2 to AGND
2.475
2.5
2.525
DC Output Voltage OUT2
(Note 2)
FB2 to OUT2
0.99
1
1.01
V OUT2
V
V+ = 4.5V to 28V,
I LOAD = 0 to 4A,
SKIP = V CC ,
0°C to +85°C
FB2 to AGND
2.463
2.5
2.537
FB2 to OUT2
0.985
1
1.015
Output Voltage Adjust Range
OUT1, OUT2
1
5.5
V
Dual-Mode Threshold, Low
OVP, FB_
0.05
0.1
0.15
V
Dual-Mode Threshold, High
OVP, ILIM_
V CC -
1.5
V CC -
0.4
V
FB1
1.9
2.0
2.1
OUT_ Input Resistance
R OUT1 V OUT1 = 1.5V
75
k Ω
R OUT2 V OUT2 = 2.5V
100
FB_ Input-Bias Current
I FB
-0.1
+0.1
µA
Soft-Start Ramp Time
Zero to full ILIM
1700
µs
2 _______________________________________________________________________________________
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Dual, High-Efficiency, Step-Down
Controller with High Impedance in Shutdown
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, V DD = V CC = 5V, SKIP = AGND, V+ = 15V, T A = 0°C to +85°C , typical values are at +25°C, unless otherwise
noted.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX UNITS
TON = AGND
120
137
153
V+ = 24V,
V OUT1 = 2V
(Note 3)
On-Time, Side 1
t ON1
TON = REF
153
174
195
ns
TON = float
222
247
272
TON = V CC
316
353
390
TON = AGND
160
182
204
V+ = 24V,
V OUT2 = 2V
(Note 3)
On-Time, Side 2
t ON2
TON = REF
205
234
263
ns
TON = float
301
336
371
TON = V CC
432
483
534
On-time 2 with
respect to on-
time 1
(Note 3)
TON = AGND
125
135
145
On-Time Tracking
TON = REF
125
135
145
%
TON = float
125
135
145
TON = V CC
125
135
145
Minimum Off-Time
t OFF
(Note 3)
400
500
ns
Quiescent Supply Current (V CC )
I CC
FB_ forced above the regulation point
1100
1500
µA
Quiescent Supply Current (V DD )
I DD
FB_ forced above the regulation point
<1
5
µA
Quiescent Supply Current (V+)
I+
Measured at V+
25
70
µA
Shutdown Supply Current (V CC )
ON1 = ON2 = AGND, OVP = V CC
<1
5
µA
Shutdown Supply Current (V DD )
ON1 = ON2 = AGND
<1
5
µA
Shutdown Supply Current (V+)
ON1 = ON2 = AGND, measured at V+,
V CC = AGND or 5V
<1
5
µA
Reference Voltage
V REF
V CC = 4.5V to 5.5V, no external REF load
1.98
2
2.02
V
Reference Load Regulation
I REF = 0 to 50µA
0.01
V
REF Sink Current
REF in regulation
10
µA
REF Fault Lockout Voltage
Falling edge, hysteresis = 40mV
1.6
V
Overvoltage Trip Threshold
(Fixed-Threshold Mode)
OVP = AGND, with respect to error-
comparator trip threshold
112
114
117
%
1V < V OVP < 1.8V, external feedback,
measured at FB_ with respect to V OVP
-28
0
+28
mV
Overvoltage Comparator Offset
(Adjustable-Threshold Mode)
1V < V OVP < 1.8V, internal feedback,
measured at OUT_ with respect to OUT_
regulation point
-3.5
0
+3.5
%
OVP Input Leakage Current
1V < V OVP < 1.8V
-100
<1
+100
nA
Overvoltage Fault Propagation
Delay
FB_ forced 2% above trip threshold
1.5
µs
Output Undervoltage Threshold
UVP = V CC , with respect to error-comparator
trip threshold
65
70
75
%
Output Undervoltage Protection
Blanking Time
From ON_ signal going high
10
30
ms
_______________________________________________________________________________________ 3
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Dual, High-Efficiency, Step-Down
Controller with High Impedance in Shutdown
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, V DD = V CC = 5V, SKIP = AGND, V+ = 15V, T A = 0°C to +85°C , typical values are at +25°C, unless otherwise
noted.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX UNITS
Current-Limit Threshold (Fixed)
AGND - V CS _, ILIM_ = V CC
40
50
60
mV
Current-Limit Threshold
(Adjustable)
AGND - V CS _, ILIM_ = 0.5V
40
50
60
mV
AGND - V CS _, ILIM_ = 1V
85
100
115
ILIM_ Adjustment Range
V ILIM _
0.3
2.5
V
Negative Current-Limit Threshold
(Fixed)
V CS _ - AGND, ILIM_ = V CC , T A = +25 o C
-75
-60
-45
mV
Thermal-Shutdown Threshold
Hysteresis = 15 o C
+160
o
C
V CC Undervoltage-Lockout
Threshold
Rising edge, hysteresis = 20mV, PWMs
disabled below this level
4.05
4.40
V
DH Gate-Driver On-Resistance
BST - LX forced to 5V
(Note 4)
MAX8743EEI
1.5
5
Ω
MAX8743ETX
1.5
6
Ω
DL Gate-Driver On-Resistance
DL, high state
(Note 4)
MAX8743EEI
1.5
5
Ω
MAX8743ETX
1.5
6
Ω
DL Gate-Driver On-Resistance
DL, low state
(Note 4)
MAX8743EEI
0.5
1.7
Ω
MAX8743ETX
0.5
2.7
Ω
DH_ Gate-Driver Source/Sink
Current
V DH _ = 2.5V, V BST _ = V LX _ = 5V
1
A
DL_ Gate-Driver Sink Current
V DL _ = 2.5V
3
A
DL_ Gate-Driver Source Current
V DL _ = 2.5V
1
A
ON_, SKIP
2.4
Logic Input High Voltage
V IH
UVP
V CC -
0.4
V
Logic Input Low Voltage
V IL
ON_, SKIP
0.8
V
UVP
0.05
V CC level
V CC -
0.4
TON Input Logic Level
Float level
3.15
3.85
V
REF level
1.65
2.35
AGND level
0.5
Logic Input Current
TON (AGND or V CC )
-3
+3
µA
Logic Input Current
ON_, SKIP, UVP
-1
+1
µA
PGOOD Trip Threshold (Lower)
With respect to error-comparator trip
threshold, falling edge
-12.5
-10
-7.5
%
PGOOD Trip Threshold (Upper)
With respect to error-comparator trip
threshold, rising edge
+7.5
+10
+12.5
%
PGOOD Propagation Delay
Falling edge, FB_ forced 2% below PGOOD
trip threshold
1.5
µs
PGOOD Output Low Voltage
I SINK = 1mA
0.4
V
PGOOD Leakage Current
High state, forced to 5.5V
1
µA
4 _______________________________________________________________________________________
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Dual, High-Efficiency, Step-Down
Controller with High Impedance in Shutdown
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 1, V DD = V CC = 5V, SKIP = AGND, V+ = 15V, T A = -40°C to +85°C , unless otherwise noted.) (Note 5)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
PWM CONTROLLERS
Input Voltage Range
V+
Battery voltage, V+
2
28
V
V CC /V DD V CC , V DD
4.5
5.5
V+ = 2V to 28V, SKIP = V CC ,
I LOAD = 0 to 8A
(Note 2)
FB1 to AGND
1.773
1.827
DC Output Voltage, OUT1
V OUT1
FB1 to V CC
1.477
1.523
V
FB1 to OUT1
0.985
1.015
DC Output Voltage, OUT2
V OUT2
V+ = 2V to 28V, SKIP = V CC ,
I LOAD = 0 to 4A (Note 2)
FB2 to AGND
2.463
2.537
V
FB2 to OUT2
0.985
1.015
Output Voltage Adjust Range
OUT1, OUT2
1.0
5.5
V
Dual-Mode Threshold, Low
OVP, FB_
0.05
0.15
V
Dual-Mode Threshold, High
OVP, ILIM_
V CC -
1.5
V CC -
0.4
V
FB_
1.9
2.1
OUT_ Input Resistance
R OUT1 V OUT1 = 1.5V
75
k
Ω
R OUT2 V OUT2 = 2.5V
100
FB_ Input Bias Current
I FB
-0.1
+0.1
µA
TON = AGND
120
153
On-Time, Side 1
t ON1
V+ = 24V, V OUT1 = 2V
(Note 3)
TON = REF
153
195
ns
TON = float
217
272
TON = V CC
308
390
TON = AGND
160
204
On-Time, Side 2
t ON2
V+ = 24V, V OUT2 = 2V
(Note 3)
TON = REF
205
263
ns
TON = float
295
371
TON = V CC
422
534
TON = AGND
125
145
On-time 2, with
respect to on-time 1
(Note 3)
On-Time Tracking
TON = REF
125
145
%
TON = float
125
145
TON = V CC
125
145
Minimum Off-Time
t OFF
(Note 3)
500
ns
Quiescent Supply Current (V CC )
I CC
FB forced above the regulation point
1500
µA
Quiescent Supply Current (V DD )
I DD
FB forced above the regulation point
5
µA
Quiescent Supply Current (V+)
I+
Measured at V+
70
µA
Reference Voltage
V REF
V CC = 4.5V to 5.5V, no external REF load
1.98
2.02
V
Reference Load Regulation
I REF = 0 to 50µA
0.01
V
Overvoltage Trip Threshold
(Fixed-Threshold Mode)
OVP = GND, with respect to FB_ regulation
point, no load
112
117
%
Output Undervoltage Threshold
UVP = V CC , with respect to FB_ regulation
point, no load
65
75
%
Current-Limit Threshold (Fixed)
AGND - V CS _, ILIM_ = V CC
35
65
mV
_______________________________________________________________________________________ 5
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