19-0839; Rev 0; 6/07
KIT
ATION
EVALU
E
BL
AVAILA
High-Efficiency, Quad-Output, Main Power-
Supply Controllers for Notebook Computers
General Description
The MAX8744A/MAX8745A are dual step-down, switch-
mode, power-supply (SMPS) controllers with synchro-
nous rectification, intended for main 5V/3.3V power
generation in battery-powered systems. Fixed-frequency
operation with optimal interleaving minimizes input rip-
ple current from the lowest input voltages up to the 26V
maximum input. Optimal 40/60 interleaving allows the
input voltage to go down to 8.3V before duty-cycle
overlap occurs, compared to 180° out-of-phase regula-
tors where the duty-cycle overlap occurs when the
input drops below 10V.
Output current sensing provides peak current-limit pro-
tection, using either an accurate sense resistor or using
lossless inductor DCR current sensing. A low-noise
mode maintains high light-load efficiency while keeping
the switching frequency out of the audible range.
An internal, fixed 5V, 100mA linear regulator powers up
the MAX8744A/MAX8745A and their gate drivers, as
well as external keep-alive loads. When the main PWM
regulator is in regulation, an automatic bootstrap switch
bypasses the internal linear regulator, providing current
up to 200mA. An additional adjustable linear-regulator
driver with an external pnp transistor can be used with
a secondary winding to provide a 12V supply, or pow-
ered directly from the main outputs to generate low-
voltage outputs as low as 1V.
Independent enable controls and power-good signals
allow flexible power sequencing. Voltage soft-start
gradually ramps up the output voltage and reduces
inrush current, while soft-shutdown gradually ramps the
output voltage down, preventing negative voltage dips.
The MAX8744A/MAX8745A feature output undervoltage
and thermal-fault protection. The MAX8744A also
includes output overvoltage-fault protection.
The MAX8744A/MAX8745A are available in a 32-pin,
5mm x 5mm, thin QFN package. The exposed back-
side pad improves thermal characteristics for demand-
ing linear keep-alive applications.
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Features
Fixed-Frequency, Current-Mode Control
40/60 Optimal Interleaving
Internal BST Switches
Internal 5V, 100mA Linear Regulator
Auxiliary Linear-Regulator Driver (12V or
Adjustable Down to 1V)
Dual Mode™ Feedback—3.3V/5V Fixed or
Adjustable Output Voltages
200kHz/300kHz/500kHz Switching Frequency
Undervoltage and Thermal-Fault Protection
Overvoltage-Fault Protection (MAX8744A Only)
6V to 26V Input Range
2V ±0.75% Reference Output
Independent Enable Inputs and Power-Good
Outputs
Soft-Start and Soft-Shutdown (Voltage Ramp)
8µA (typ) Shutdown Current
MAX8744A/MAX8745A
Ordering Information
PART
MAX8744AETJ+
TEMP RANGE
-40°C to +85°C
PIN-
PACKAGE
PKG
CODE
32 Thin QFN
T3255-4
(5mm x 5mm)
32 Thin QFN
T3255-4
(5mm x 5mm)
MAX8745AETJ+*
-40°C to +85°C
+Denotes
a lead-free package.
*Future
product—contact factory for availability.
Pin Configuration
PGOODA
LDO5
DL3
DL5
18
LX3
LX5
17
16
15
14
13
DH5
BST5
PGOOD5
CSL5
CSH5
FB5
SKIP
FSEL
12
11
+
1
ONA
2
DRVA
3
ILIM
4
SHDN
5
ON3
6
ON5
7
REF
8
GND
10
9
TOP VIEW
24
DH3 25
BST3 26
PGOOD3 27
CSL3 28
CSH3 29
FB3 30
FBA 31
OUTA 32
23
22
21
20
19
Applications
Main Power Supplies
2 to 4 Li+ Cell Battery-Powered Devices
Notebook and Subnotebook Computers
PDAs and Mobile Communicators
MAX8744A
MAX8745A
Dual Mode is a trademark of Maxim Integrated Products, Inc.
THIN QFN
5mm x 5mm
________________________________________________________________
Maxim Integrated Products
PGND
IN
1
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.
High-Efficiency, Quad-Output, Main Power-
Supply Controllers for Notebook Computers
MAX8744A/MAX8745A
ABSOLUTE MAXIMUM RATINGS
IN,
SHDN,
DRVA, OUTA to GND............................-0.3V to +28V
LDO5, ON3, ON5, ONA to GND ..............................-0.3V to +6V
PGOODA, PGOOD3, PGOOD5 to GND...................-0.3V to +6V
CSL3, CSH3, CSL5, CSH5 to GND ..........................-0.3V to +6V
REF, FB3, FB5, FBA to GND...................-0.3V to (V
LDO5
+ 0.3V)
SKIP,
FSEL, ILIM to GND........................-0.3V to (V
LDO5
+ 0.3V)
DL3, DL5 to PGND..................................-0.3V to (V
LDO5
+ 0.3V)
BST3, BST5 to PGND .............................................-0.3V to +34V
BST3 to LX3..............................................................-0.3V to +6V
DH3 to LX3 ..............................................-0.3V to (V
BST3
+ 0.3V)
BST5 to LX5..............................................................-0.3V to +6V
DH5 to LX5 ..............................................-0.3V to (V
BST5
+ 0.3V)
GND to PGND .......................................................-0.3V to +0.3V
BST3, BST5 to LDO5 .............................................-0.3V to +0.3V
LDO Short Circuit to GND ..........................................Momentary
REF Short Circuit to GND ...........................................Momentary
DRVA Current (Sinking) ......................................................30mA
OUTA Shunt Current ...........................................................30mA
Continuous Power Dissipation (T
A
= +70°C)
Multilayer PCB
32-Pin, 5mm x 5mm TQFN
(derated 34.5mW/°C above +70°C) .........................2459mW
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
IN
= 12V, both SMPS enabled, FSEL = REF,
SKIP
= GND, ILIM = LDO5, FBA = LDO5, I
REF
= I
LDO5
= I
OUTA
=
no load,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
INPUT SUPPLIES (Note 1)
V
IN
Input Voltage Range
V
IN
Operating Supply Current
V
IN
Standby Supply Current
V
IN
Shutdown Supply Current
V
IN
I
IN
I
IN(STBY)
I
IN(SHDN)
LDO5 in regulation
IN = LDO5, V
CSL5
< 4.4V
LDO5 switched over to CSL5, either
SMPS on
V
IN
= 6V to 26V, both SMPS off, includes
I
SHDN
V
IN
= 6V to 26V
Both SMPS on, FB3 = FB5 = LDO5,
SKIP
= GND, V
CSL3
= 3.5V, V
CSL5
= 5.3V,
V
OUTA
= 15V,
P
IN
+ P
CSL3
+ P
CSL5
+ P
OUTA
5.4
4.5
20
65
8
26.0
5.5
36
120
20
V
µA
µA
µA
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Quiescent Power Consumption
P
Q
3.5
4.5
mW
MAIN SMPS CONTROLLERS
3.3V Output Voltage in Fixed
Mode
5V Output Voltage in Fixed Mode
V
OUT3
V
OUT5
V
IN
= 6V to 26V,
SKIP
= FB3 = LDO5,
0 < V
CSH3
- V
CSL3
< 50mV (Note 2)
V
IN
= 6V to 26V,
SKIP
= FB5 = LDO5,
0 < V
CSH5
- V
CSL5
< 50mV (Note 2)
V
IN
= 6V to 26V, FB3 or FB5
duty factor = 20% to 80%
V
FB_
V
IN
= 6V to 26V, FB3 or FB5
duty factor = 50%
3.265
4.94
1.980
1.990
3.315
5.015
2.010
2.010
3.365
5.09
2.040
V
2.030
V
V
Feedback Voltage in Adjustable
Mode (Note 2)
2
_______________________________________________________________________________________
High-Efficiency, Quad-Output, Main Power-
Supply Controllers for Notebook Computers
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, V
IN
= 12V, both SMPS enabled, FSEL = REF,
SKIP
= GND, ILIM = LDO5, FBA = LDO5, I
REF
= I
LDO5
= I
OUTA
=
no load,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
Output Voltage Adjust Range
FB3, FB5 Dual Mode Threshold
Feedback Input Leakage Current
DC Load Regulation
Line Regulation Error
Operating Frequency (Note 1)
Maximum Duty Factor
Minimum On-Time
SMPS3-to-SMPS5 Phase Shift
CURRENT LIMIT
ILIM Adjustment Range
Current-Sense Input Leakage
Current
Current-Limit Threshold (Fixed)
Current-Limit Threshold
(Adjustable)
Current-Limit Threshold
(Negative)
Current-Limit Threshold
(Zero Crossing)
V
LIMIT
V
LIMIT
CSH3 = CSH5 = GND or LDO5
V
CSH
_ - V
CSL
_, ILIM = LDO5
V
CSH
_ - V
CSL
_
V
ILIM
= 2.00V
V
ILIM
= 1.00V
0.5
-1
45
185
94
-67
50
200
100
-60
-120
0
6
3
10
20
2.5
5
10
-1
+1
7.5
6
14
V
REF
+1
55
215
106
-53
V
µA
mV
mV
mV
%
mV
mV
%
mV
%
µA
f
OSC
D
MAX
t
ONMIN
SMPS5 starts after SMPS3
V
FB3
= V
FB5
= 2.1V
Either SMPS,
SKIP
= LDO5,
0 < V
CSH_
- V
CSL_
< 50mV
Either SMPS, 6V < V
IN
< 26V
FSEL = GND
FSEL = REF
FSEL = LDO5
(Note 1)
170
270
425
97.5
SYMBOL
Either SMPS
CONDITIONS
MIN
2.0
3.0
-0.1
-0.1
0.03
200
300
500
99
100
40
144
230
330
575
%
ns
%
Deg
kHz
V
LOO5
- 1.0
TYP
MAX
5.5
V
LOO5
- 0.4
+0.1
UNITS
V
V
µA
%
%/V
MAX8744A/MAX8745A
V
CSH
_ - V
CSL
_,
SKIP
= ILIM = LDO5
V
NEG
V
CSH
_ - V
CSL
_,
SKIP
= LDO5, adjustable
mode, percent of current limit
V
CSH
_ - V
CSL
_,
SKIP
= GND,
ILIM = LDO5
ILIM = LDO5
V
ZX
Idle Mode™ Threshold
V
IDLE
V
CSH
_ - V
CSL
_,
SKIP
= GND
With respect to
current-limit
threshold (V
LIMIT
)
ILIM = LDO5
Idle Mode Threshold
(Low Audible-Noise Mode)
ILIM Leakage Current
V
IDLE
V
CSH
_ - V
CSL
_,
SKIP
= REF
ILIM = GND or REF
With respect to
current-limit
threshold (V
LIMIT
)
Idle Mode is a trademark of Maxim Integrated Products, Inc.
_______________________________________________________________________________________
3
High-Efficiency, Quad-Output, Main Power-
Supply Controllers for Notebook Computers
MAX8744A/MAX8745A
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, V
IN
= 12V, both SMPS enabled, FSEL = REF,
SKIP
= GND, ILIM = LDO5, FBA = LDO5, I
REF
= I
LDO5
= I
OUTA
=
no load,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
Soft-Start Ramp Time
Soft-Stop Ramp Time
SYMBOL
t
SSTART
t
SSTOP
CONDITIONS
Measured from the rising edge of ON_ to
full scale
Measured from the falling edge of ON_ to
full scale
MIN
TYP
2
4
MAX
UNITS
ms
ms
INTERNAL FIXED LINEAR REGULATORS
LDO5 Output Voltage
LDO5 Undervoltage-Lockout Fault
Short-Circuit Current (Switched
Over to CSL5)
AUXILIARY LINEAR REGULATOR
DRVA Voltage Range
DRVA Drive Current
FBA Regulation Threshold
FBA Load Regulation
OUTA Shunt Trip Level
FBA Leakage Current
Secondary Feedback Regulation
Threshold
DL5 Pulse Width
OUTA Leakage Current
REFERENCE (REF)
Reference Voltage
Reference Load-Regulation Error
REF Lockout Voltage
FAULT DETECTION
Output Overvoltage Trip Threshold
(MAX8744A Only)
Output Overvoltage Fault
Propagation Delay (MAX8744A Only)
t
OVP
With respect to error-comparator
threshold
50mV overdrive
8
11
10
14
%
µs
V
REF
ΔV
REF
V
REF(UVLO)
LDO5 in regulation, I
REF
= 0
I
REF
= -5µA to +50µA
Rising edge
1.985
-10
1.8
2.00
2.015
+10
V
mV
V
I
OUTA
V
DRVA
= V
OUTA
= 25V
V
FBA
V
DRVA
V
FBA
= 1.05V, V
DRVA
= 5V
V
FBA
= 0.965V, V
DRVA
= 5V
V
DRVA
= 5V, I
DRVA
= 1mA (sink)
V
DRA
= 5V, I
DRVA
= 0.5mA to 5mA
Rising edge
V
FBA
= 1.035V
V
DRVA
- V
OUTA
25
-0.1
0
1/
3f
OSC
50
10
0.98
1.00
-1.2
26
1.02
-2.2
27
+0.1
0.5
26.0
0.4
V
mA
V
%
V
µA
V
µs
µA
V
LDO5
ON5 = GND, 6V < V
IN
< 26V,
0 < I
LDO5
< 100mA
Rising edge, hysteresis = 1%
LDO5 = GND, V
CSL5
> 4.7V
4.85
3.7
200
4.95
4.0
425
5.10
4.1
V
V
mA
4
_______________________________________________________________________________________
High-Efficiency, Quad-Output, Main Power-
Supply Controllers for Notebook Computers
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, V
IN
= 12V, both SMPS enabled, FSEL = REF,
SKIP
= GND, ILIM = LDO5, FBA = LDO5, I
REF
= I
LDO5
= I
OUTA
=
no load,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
Output Undervoltage Protection
Trip Threshold
Output Undevoltage Fault
Propagation Delay
Output Undervoltage Protection
Blanking Time
PGOOD_ Lower Trip Threshold
PGOOD_ Propagation Delay
PGOOD_ Output Low Voltage
PGOOD_ Leakage Current
Thermal-Shutdown Threshold
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
Dead Time
Internal BST_ Switch
On-Resistance
BST_ Leakage Current
INPUTS AND OUTPUTS
SHDN
Input Trip Level
ONA Logic Input Voltage
Rising trip level
Falling trip level
Hysteresis = 600mV (typ)
SMPS off level/clear fault level
ON3, ON5 Input Voltage
Delay start level
SMPS on level
1.9
2.4
High
Low
1.1
0.96
2.4
0.8
0.8
2.1
V
1.6
1
2.2
1.04
V
V
R
DH
R
DL
I
DH
I
DL
I
DL (SINK)
t
DEAD
R
BST
BST_ – LX_ forced to 5V
DL_, high state
DL_, low state
DH_ forced to 2.5V, BST_ - LX_ forced to
5V
DL_ forced to 2.5V
DL_ forced to 2.5V
DH_low to DL_high
DL_low to DH_high
I
BST
= 10mA
V
BST
_ = 26V
15
15
1.3
1.7
0.6
2
1.7
3.3
45
44
5
2
20
5
5
3
Ω
Ω
A
A
A
ns
Ω
µA
I
PGOOD
_
t
SHDN
t
PGOOD
_
t
UVP
t
BLANK
SYMBOL
CONDITIONS
With respect to error-comparator
threshold
50mV overdrive
From rising edge of ON_ with respect to
f
SW
With respect to error-comparator
threshold, hysteresis = 1% (typ)
Falling edge, 50mV overdrive
Rising edge, 50mV overdrive
I
SINK
= 1mA
High state, PGOOD_ forced to 5.5V
Hysteresis = 15°C
+160
5000
-12
MIN
65
TYP
70
10
6144
-10
10
1
0.4
1
7000
-8
MAX
75
UNITS
%
µs
1/f
OSC
%
µs
V
µA
°C
MAX8744A/MAX8745A
_______________________________________________________________________________________
5
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