Maxim Integrated MAX1540, MAX1541 Schematic
General Description
The MAX1540/MAX1541 dual pulse-width modulation
(PWM) controllers provide 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 Maxim proprietary Quick-PWM™ controllers are
free running, constant on-time with input feed forward.
This configuration provides ultra-fast transient
response, wide input-output (I/O) differential range, low
supply current, and tight load-regulation characteristics. The controllers can accurately sense the inductor
current across an external current-sense resistor in
series with the output to ensure reliable overload and
inductor saturation protection. Alternatively, the controllers can use the synchronous rectifier itself or lossless inductor current-sensing methods to provide
overload protection with lower power dissipation.
For a single step-down PWM controller with inductorsaturation protection, external-reference input voltage,
and dynamically selectable output voltages, refer to the
MAX1992/MAX1993 data sheet.
Applications
Notebook Computers
Core/IO Supplies as Low as 0.7V
0.7V to 5.5V Supply Rails
CPU/Chipset/GPU with Dynamic Voltage Core
Supplies (MAX1541)
DDR Memory Termination (MAX1541)
Active Termination Buses (MAX1541)
Features
♦ Inductor-Saturation Protection
♦ Accurate Differential Current-Sense Inputs
♦ Dual Ultra-High-Efficiency Quick-PWMs with
100ns Load-Step Response
♦ MAX1540
1.8V/1.2V Fixed or 0.7V to 5.5V Adjustable
Output (OUT1)
2.5V/1.5V Fixed or 0.7V to 5.5V Adjustable
Output (OUT2)
Fixed 5V, 100mA Linear Regulator
♦ MAX1541
External Reference Input (REFIN1)
Dynamically Selectable Output Voltage—0.7V
to 5.5V (OUT1)
2.5V/1.8V Fixed or 0.7V to 5.5V Adjustable
Output (OUT2)
Optional Power-Good and Fault Blanking
During Transitions
Fixed 5V or Adjustable 100mA Linear Regulator
♦ 1% V
OUT
Accuracy over Line and Load
♦ 2V to 28V Battery Input Range
♦ 170kHz to 620kHz Selectable Switching
Frequency
♦ Overvoltage/Undervoltage-Protection Option
♦ 1.7ms Digital Soft-Start
♦ Drives Large Synchronous-Rectifier FETs
♦ 2V ±0.7% Reference Output
♦ Separate Power-Good Window Comparators
MAX1540/MAX1541
Dual Step-Down Controllers with Saturation
Protection, Dynamic Output, and Linear Regulator
________________________________________________________________ Maxim Integrated Products 1
THIN QFN
TOP VIEW
32313029282726
ON1
ON2
CSP1
CSN1
FB1
OUT1
PGOOD1
25 DH1
9
1011121314
15
CSP2
CSN2
FB2
OUT2
PGOOD2
DH2
LX2
16BST2
17
18
19
20
21
22
23
GND
DL2
V+
LDOOUT
DL1
LDOON
BST1
8
7
6
5
4
3
2
REF
ILIM2
ILIM1
V
CC
TON
LSAT
SKIP
MAX1540
1OVP/UVP
24 LX1
Pin Configurations
19-2861; Rev 2; 1/05
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.
EVALUATION KIT
AVAILABLE
Quick-PWM is a trademark of Maxim Integrated Products, Inc.
Ordering Information
PART
PIN-PACKAGE
MAX1540ETJ
32 Thin QFN 5mm x 5mm
MAX1541ETL
40 Thin QFN 6mm x 6mm
Pin Configurations continued at end of data sheet.
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
MAX1540/MAX1541
Dual Step-Down Controllers with Saturation
Protection, Dynamic Output, and Linear Regulator
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
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.
Note 1: For the MAX1540, the gate-driver input supply (VDD) is internally connected to the fixed 5V linear-regulator output (LDOOUT),
and the linear-regulator input supply (LDOIN) is internally connected to the battery voltage input (V+).
V+, LDOON to GND ...............................................-0.3V to +28V
LDOOUT to GND (MAX1540, Note 1) ......................-0.3V to +6V
LDOOUT to GND (MAX1541, Note 1) ....................-0.3V to +28V
V
DD
to GND (MAX1541, Note 1) ..............................-0.3V to +6V
V
CC
, ON_ to GND.....................................................-0.3V to +6V
SKIP, PGOOD_ to GND............................................-0.3V to +6V
FB_, CSP_, ILIM_ to GND.........................................-0.3V to +6V
TON, OVP/UVP, LSAT to GND ...................-0.3V to (V
CC
+ 0.3V)
REF, OUT_ to GND.....................................-0.3V to (V
CC
+ 0.3V)
LDOIN to GND (MAX1541).....................................-0.3V to +28V
REFIN1, GATE, OD, FBLDO to GND (MAX1541).....-0.3V to +6V
FBLANK, CC1 to GND (MAX1541).............-0.3V to (V
CC
+ 0.3V)
DL_ to GND (Note 1) ..................................-0.3V to (V
DD
+ 0.3V)
CSN_ to GND ............................................................-2V to +30V
DH_ to LX_..................................................-0.3V to (BST + 0.3V)
LX_ to GND................................................................-2V to +30V
BST_ to LX_ ..............................................................-0.3V to +6V
REF Short Circuit to GND ...........................................Continuous
Continuous Power Dissipation (T
A
= +70°C)
32-Pin 5mm x 5mm Thin QFN (derated 21.3mW/°C
above +70°C).............................................................1702mW
40-Pin 6mm x 6mm Thin QFN (derated 26.3mW/°C
above +70°C).............................................................2105mW
Operating Temperature Range
MAX154_ET_ ...................................................-40°C to +85°C
Junction Temperature......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
ELECTRICAL CHARACTERISTICS
(V+ = 15V, VCC= VDD= ON1 = ON2 = 5V, SKIP = GND, LDOIN (MAX1541) = V+, TA= 0°C to +85°C, unless otherwise noted. Typical
values are at T
A
= +25°C.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
INPUT SUPPLIES (Note 1)
MAX1540: battery voltage, V+ > V
LDOOUT
5.5 28
V
IN
MAX1541: battery voltage, V+ > V
LDOOUT
228
V
BIAS
V
CC, VDD
(MAX1541) 4.5 5.5Input Voltage Range
V
LDOIN
MAX1541: LDO input supply,
V
LDOIN
> V
LDOOUT
4.5 28
V
FB1 and FB2 forced above the regulation
point, LSAT = GND
0.7 1.5
Quiescent Supply Current (VCC)I
CC
FB1 and FB2 forced above the regulation
point, ON1 or ON2 = V
CC
, V
LSAT
> 0.5V
1.8
mA
Quiescent Supply Current
(V
DD
, MAX1541 Only)
I
DD
FB1 and FB2 forced above the regulation
point, ON1 or ON2 = V
CC
<1 5 µA
MAX1540: FB1 and FB2 forced above the
regulation point, ON1 or ON2 = V
CC
,
V
LDOON
= V+ = 28V
150
Quiescent Supply Current (V+) I
V+
MAX1541: ON1 or ON2 = VCC,
V
LDOON
= V+ = 28V
25 40
µA
Quiescent Supply Current
(LDOIN, MAX1541 Only)
I
LDOIN
FB1 and FB2 forced above the regulation
point, ON1 or ON2 = V
CC
,
V
LDOON
= V+ = 28V
110 µA
Standby Supply Current (VCC) ON1 = ON2 = GND, V
LDOON
= V+ = 28V <1 5 µA
MAX1540/MAX1541
Dual Step-Down Controllers with Saturation
Protection, Dynamic Output, and Linear Regulator
_______________________________________________________________________________________ 3
ELECTRICAL CHARACTERISTICS (continued)
(V+ = 15V, VCC= VDD= ON1 = ON2 = 5V, SKIP = GND, LDOIN (MAX1541) = V+, TA= 0°C to +85°C, unless otherwise noted. Typical
values are at T
A
= +25°C.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Standby Supply Current
(V
DD
, MAX1541 Only)
ON1 = ON2 = GND, V
LDOON
= V+ = 28V <1 5 µA
MAX1540: ON1 = ON2 = GND,
LDOON = V+ = 28V, V
CC
= 0 or 5V
105
Standby Supply Current (V+)
MAX1541: ON1 = ON2 = GND,
LDOON = V+ = 28V, V
CC
= VDD = 0 or 5V
<1 5
µA
Standby Supply Current
(LDOIN, MAX1541 Only)
ON1 = ON2 = GND, V
LDOON
= V+ = 28V 100 µA
Shutdown Supply Current (VCC) ON1 = ON2 = LDOON = GND <1 5 µA
Shutdown Supply Current
(V
DD
, MAX1541 Only)
ON1 = ON2 = LDOON = GND <1 5 µA
MAX1540: ON1 = ON2 = LDOON = GND,
V+ = 28V, V
CC
= 0 or 5V
415
Shutdown Supply Current (V+)
MAX1541: ON1 = ON2 = LDOON = GND,
V+ = 28V, V
CC
= VDD = 0 or 5V
<1 5
µA
Shutdown Supply Current
(LDOIN, MAX1541 Only)
LDOON = GND 4 10 µA
PWM CONTROLLERS
FB1 = GND
V
OUT1
Preset output,
V+ = 5.5V to 28V,
SKIP = V
CC
FB1 = V
CC
MAX1540 Main Output-Voltage
Accuracy (OUT1) (Note 2)
V
FB1
Adjustable output, V+ = 5.5V to 28V,
SKIP = V
CC
V
FB2 = GND
V
OUT2
Preset output,
V+ = 5.5V to 28V,
SKIP = V
CC
FB2 = V
CC
MAX1540 Secondary OutputVoltage Accuracy (OUT2)
(Note 2)
V
FB2
Adjustable output, V+ = 5.5V to 28V,
SKIP = V
CC
V
MAX1541 Main FeedbackVoltage Accuracy (FB1)
V
FB1
V+ = 4.5V to 28V,
SKIP = V
CC
V
FB2 = GND
V
OUT2
Preset output,
V+ = 4.5V to 28V,
SKIP = V
CC
FB2 = V
CC
MAX1541 Secondary OutputVoltage Accuracy (OUT2)
(Note 2)
V
FB2
Adjustable output, V+ = 4.5V to 28V,
SKIP = V
CC
V
Load-Regulation Error I
LOAD
= 0 to 3A, SKIP = V
CC
0.1 %
Line-Regulation Error VCC = 4.5V to 5.5V, V+ = 4.5V to 28V
%
FB_ Input Bias Current IFB_
µA
Output Adjust Range 0.7 5.5 V
REFIN1 = 0.35 x REF 0.693 0.70 0.707
1.782 1.80 1.818
1.188 1.20 1.212
0.693 0.70 0.707
2.475 2.50 2.525
1.485 1.50 1.515
0.693 0.70 0.707
2.475 2.50 2.525
1.782 1.80 1.818
0.693 0.70 0.707
-0.1 +0.1
0.25
MAX1540/MAX1541
Dual Step-Down Controllers with Saturation
Protection, Dynamic Output, and Linear Regulator
4 _______________________________________________________________________________________
ELECTRICAL CHARACTERISTICS (continued)
(V+ = 15V, VCC= VDD= ON1 = ON2 = 5V, SKIP = GND, LDOIN (MAX1541) = V+, TA= 0°C to +85°C, unless otherwise noted. Typical
values are at T
A
= +25°C.)
PARAMETER
CONDITIONS
UNITS
FB_ = GND 70
350
MAX1540
FB_ = V
CC
or
adjustable
50
220
FB1 = OUT1
FB2 = GND 90
350
OUT_ Input Resistance R
OUT
_
MAX1541
FB2 = V
CC
or
adjustable
60
270
kΩ
OUT_ Discharge Mode OnResistance
10 25 Ω
OUT_ Synchronous-Rectifier
Discharge-Mode Turn-On Level
0.2 0.3 0.4 V
Soft-Start Ramp Time t
SS
Rising edge on ON_ to full current limit 1.7 ms
TON = GN D ( 620kH z)
190
242
335
DH1 On-Time t
ON1
V+ = 15V,
V
OUT1
= 1.5V
(Note 3)
491
ns
256
331
453
DH2 On-Time t
ON2
V+ = 15V,
V
OUT2
= 1.5V
(Note 3)
679
ns
On-Time Tracking t
ON2
with respect to t
ON1
(Note 3)
150 %
Minimum Off-Time
)
(Note 3)
500 ns
LINEAR REGULATOR (LDO) (Note 1)
5.0
MAX1540 LDO Output-Voltage
Accuracy
ON1 = ON2 = GND,
V+ = 6V to 28V
V
5.0
MAX1541 LDO Output-Voltage
Accuracy (Fixed V
LDOOUT
)
FBLDO = ON1 =
ON2 = GND,
V
MAX1541 LDO Feedback
FBLDO = LDOOUT,
ON1 = ON2 = GND,
V
LDOIN
= 4.5V to
28V
V
MAX1541 LDO Output
Adjust Range
24 V
LDOOUT Short-Circuit Current
mA
FBLDO Input Bias Current I
FBLDO
µA
800
Dropout Voltage
MAX1541: V
LDOIN
- V
LDOOUT
,
I
LDOOUT
= 50mA
800
mV
Accuracy (Adjustable V
LDOOUT
)
SYMBOL
MIN TYP MAX
145
115
400 700 1500
170
130
R
D IS C H ARGE
TON = REF (485kHz) 191 216
149 169
TON = op en ( 345kH z) 274 304
TON = VCC (235kHz) 402 447
TON = GN D ( 460kH z) 201 228
TON = REF (355kHz) 260 296
TON = op en ( 255kH z) 371 412
TON = VCC (170kHz) 556 618
t
OFF(MIN
120 135
400
V
LDOOUT
V
LDOOUT
V
LDOIN
V
FBLDO
= 6V to 28V
0 < I
0 < I
0 < I
0 < I
0 < I
0 < I
LD OOU T
LD OOU T
LD OOU T
< 10mA 4.85
LDOOUT
< 100m A 4.70 5.10
< 10mA 4.85
LDOOUT
< 100m A 4.70 5.10
< 10mA 1.212 1.25 1.275
LDOOUT
< 100m A 1.175 1.275
1.175
130
-0.1 +0.1
MAX1540: V+ - V
LDOOUT
, I
LDOOUT
= 50mA 500
500
5.10
5.10
MAX1540/MAX1541
Dual Step-Down Controllers with Saturation
Protection, Dynamic Output, and Linear Regulator
_______________________________________________________________________________________ 5
ELECTRICAL CHARACTERISTICS (continued)
(V+ = 15V, VCC= VDD= ON1 = ON2 = 5V, SKIP = GND, LDOIN (MAX1541) = V+, TA= 0°C to +85°C, unless otherwise noted. Typical
values are at T
A
= +25°C.)
PARAMETER
CONDITIONS
UNITS
REFERENCE (REF)
Reference Voltage V
REF
VCC = 4.5V to 5.5V,
I
REF
= 0V
T
A
= 0° C to +85°C
V
Reference Load Regulation ∆V
REFIREF
= -10µA to +50µA
V
REF Lockout Voltage
)
Rising edge, hysteresis = 350mV
V
REFIN1 (MAX1541)
Voltage Range
V
REFIN
0.7
V
REFIN1 (MAX1541)
Input Bias Current
I
REFIN1
µA
FAULT DETECTION
Overvoltage Trip Threshold
With respect to error-comparator threshold,
OVP/UVP = V
CC
12 16 20 %
Overvoltage Fault-Propagation
Delay
t
OVP
FB forced 2% above trip threshold 10 µs
Output Undervoltage-Protection
Trip Threshold
With respect to error-comparator threshold,
OVP/UVP = V
CC
65 70 75 %
Output Undervoltage-Protection
Blanking Time
t
BLANK
From rising edge of ON_ 10 35 ms
Output Undervoltage FaultPropagation Delay
t
UVP
10 µs
PGOOD_ Lower Trip Threshold
With respect to error-comparator threshold,
hysteresis = 1%
-13 -10 -7 %
PGOOD_ Upper Trip Threshold
With respect to error-comparator threshold,
hysteresis = 1%
+7
%
PGOOD_ Propagation Delay
10 µs
PGOOD_ Output Low Voltage I
SINK
= 4mA 0.3 V
PGOOD_ Leakage Current
FB = REF (PGOOD high impedance),
PGOOD forced to 5.5V
1µA
FBLANK = V
CC
320
FBLANK = open 80
205
Fault-Blanking Time
(MAX1541 Only)
FBLANK = REF 35 65 95
µs
LDOON = V
CC
Thermal-Shutdown Threshold T
SHDN
Hysteresis = 10°C
LDOON = GND
°C
VCC Undervoltage-Lockout
Threshold
)
Rising edge, PWM disabled below this
level, hysteresis = 20mV
4.1
4.4 V
CURRENT LIMIT
ILIM_ Adjustment Range
2V
CSP_ 0 2.7
Current-Limit Input Range
CSN_
V
CSP_/CSN_ Input Current 0.5 µA
SYMBOL
TA = + 25° C to + 85° C 1.986 2.00 2.014
V
REF(UVLO
t
PGOOD
I
PGOOD
t
FBLANK
V
UVLO(VCC
FB forced 2% beyond P GOOD _ trip threshold
_
_
MIN TYP MAX
1.983 2.00 2.017
-0.01 +0.01
1.95
0.01 0.05
+10 +13
120 220
0.25
-0.3 +28
140
+150
+160
4.25
V
REF
MAX1540/MAX1541
Dual Step-Down Controllers with Saturation
Protection, Dynamic Output, and Linear Regulator
6 _______________________________________________________________________________________
Dual Mode is a trademark of Maxim Integrated Products, Inc.
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Valley Current-Limit Threshold
(Fixed)
)
V
CSP
_ - V
CSN
_, ILIM_ = V
CC
45 50 55 mV
V
ILIM
_ = 250mV 15 25 35
Valley Current-Limit Threshold
(Adjustable)
)
V
CSP
_ - V
CSN
_
V
ILIM
_ = 2.00V
230
mV
Current-Limit Threshold
(Negative)
V
NEG
V
CSP
_ - V
CSN
_, SKIP = ILIM_ = VCC,
T
A
= +25°C
-90 -65 -45 mV
Current-Limit Threshold
(Zero Crossing)
V
ZX
With respect to valley current-limit
threshold, V
CSP
_ - V
CSN
_, SKIP = GND,
ILIM_ = V
CC
2.5 mV
LSAT = V
CC
220
LSAT = open
193
Inductor-Saturation Current-Limit
Threshold
With respect to
valley currentlimit threshold,
ILIM_ = V
CC
LSAT = REF
165
%
ILIM_ Saturation Fault Sink
Current
)
V
CSP
- V
CSN
> inductor saturation current
limit, 0.25V < V
ILIM
_ < 2.0V
468µA
ILIM_ Leakage Current
V
CSP
_ - V
CSN _
< inductor saturation current
limit
0.1 µA
GATE DRIVERS
DH_ Gate-Driver On-Resistance R
DH
BST_-LX_ forced to 5V 1.5 5 Ω
DL_, high state 1.5 5
DL_ Gate-Driver On-Resistance R
DL
DL_, low state 0.6 3
Ω
DH_ Gate-Driver Source/Sink
Current
I
DH
1A
DL_ Gate-Driver Source Current
I
DL
(
)
DL_ forced to 2.5V 1 A
DL_ Gate-Driver Sink Current
)
DL_ forced to 2.5V 3 A
DL_ rising 35
Dead Time t
DEAD
DH_ rising 26
ns
INPUTS AND OUTPUTS
OD On-Resistance R
OD
GATE = V
CC
10 25 Ω
OD Leakage Current GATE = GND, OD forced to 5.5V 1 200 nA
Logic Input Threshold
ON1, ON2, SKIP, GATE rising edge,
hysteresis = 225mV
1.2 1.7 2.2 V
LDOON Input Trip Level Rising edge, hysteresis = 250mV
V
Logic Input Current ON1, ON2, LDOON, SKIP, GATE -1 +1 µA
High 1.9 2.0 2.1
Dual Mode™ Threshold Voltage
MAX1541)
Low
0.1
V
ELECTRICAL CHARACTERISTICS (continued)
(V+ = 15V, VCC= VDD= ON1 = ON2 = 5V, SKIP = GND, LDOIN (MAX1541) = V+, TA= 0°C to +85°C, unless otherwise noted. Typical
values are at T
A
= +25°C.)
V
LIM_ (VAL
V
LIM_ (VAL
170 200
I
ILIM_ (LSAT
SOURCE
I
DL (SINK
DH_ forced to 2.5V, BST_-LX_ forced to 5V
FB1 (MAX1540),
FB2 (MAX1540/
180 200
157 175
135 150
1.20 1.25 1.30
0.05
0.15
MAX1540/MAX1541
Dual Step-Down Controllers with Saturation
Protection, Dynamic Output, and Linear Regulator
_______________________________________________________________________________________ 7
ELECTRICAL CHARACTERISTICS (continued)
(V+ = 15V, VCC= VDD= ON1 = ON2 = 5V, SKIP = GND, LDOIN (MAX1541) = V+, TA= 0°C to +85°C, unless otherwise noted. Typical
values are at T
A
= +25°C.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
High
V
CC
-
Open
REF
Four-Level Input Logic Levels
TON, OVP/UVP,
LSAT, SKIP,
FBLANK
Low 0.5
V
Four-Level Logic Input Current
TON, OVP/UVP, LSAT, SKIP, FBLANK
forced to GND or V
CC
-3 +3 µA
ELECTRICAL CHARACTERISTICS
(V+ = 15V, VCC= VDD= ON1 = ON2 = 5V, SKIP = GND, LDOIN (MAX1541) = V+, TA= -40°C to +85°C, unless otherwise noted.) (Note 4)
PARAMETER
CONDITIONS
INPUT SUPPLIES (Note 1)
MAX1540: battery voltage, V+ > V
LDOOUT
5.5 28
V
IN
MAX1541: battery voltage, V+ > V
LDOOUT
228
V
BIAS
V
CC, VDD
(MAX1541) 4.5 5.5Input Voltage Range
V
LDOIN
MAX1541: LDO input supply,
V
LDOIN
> V
LDOOUT
4.5 28
V
FB1 and FB2 forced above the regulation
point, LSAT = GND
1.5
Quiescent Supply Current (VCC)I
CC
FB1 and FB2 forced above the regulation
point, ON1 or ON2 = V
CC
, V
LSAT
> 0.5V
1.8
mA
Quiescent Supply Current
(V
DD
, MAX1541 Only)
I
DD
FB1 and FB2 forced above the regulation
point, ON1 or ON2 = V
CC
5µA
MAX1540: FB1 and FB2 forced above the
regulation point, ON1 or ON2 = V
CC
,
V
LDOON
= V+ = 28V
150
Quiescent Supply Current (V+) I
V+
MAX1541: ON1 or ON2 = VCC, V
LDOON
=
V+ = 28V
40
µA
Quiescent Supply Current
(LDOIN, MAX1541 Only)
I
LDOIN
FB1 and FB2 forced above the regulation
point, ON1 or ON2 = V
CC
,
V
LDOON
= V+ = 28V
110 µA
Standby Supply Current (VDD) ON1 = ON2 = GND, V
LDOON
= V+ = 28V 5 µA
Standby Supply Current
(V
DD
, MAX1541 Only)
ON1 = ON2 = GND, V
LDOON
= V+ = 28V 5 µA
MAX1540: ON1 = ON2 = GND, LDOON =
V+ = 28V, V
CC
= 0 or 5V
105
Standby Supply Current (V+)
MAX1541: ON1 = ON2 = GND, LDOON =
V+ = 28V, V
CC
= VDD = 0 or 5V
5
µA
Standby Supply Current
(LDOIN, MAX1541 Only)
ON1 = ON2 = GND, V
LDOON
= V+ = 28V 100 µA
SYMBOL
0.4V
3.15 3.85
1.65 2.35
MIN MAX UNITS
MAX1540/MAX1541
Dual Step-Down Controllers with Saturation
Protection, Dynamic Output, and Linear Regulator
8 _______________________________________________________________________________________
ELECTRICAL CHARACTERISTICS (continued)
(V+ = 15V, VCC= VDD= ON1 = ON2 = 5V, SKIP = GND, LDOIN (MAX1541) = V+, TA= -40°C to +85°C, unless otherwise noted.)
(Note 4)
PARAMETER
CONDITIONS
UNITS
Shutdown Supply Current (VCC) ON1 = ON2 = LDOON = GND 5 µA
Shutdown Supply Current
(V
DD
, MAX1541 Only)
ON1 = ON2 = LDOON = GND 5 µA
MAX1540: ON1 = ON2 = LDOON = GND,
V+ = 28V, V
CC
= 0 or 5V
15
Shutdown Supply Current (V+)
MAX1541: ON1 = ON2 = LDOON = GND,
V+ = 28V, V
CC
= VDD = 0 or 5V
5
µA
Shutdown Supply Current
(LDOIN, MAX1541 Only)
LDOON = GND 10 µA
PWM CONTROLLERS
FB1 = GND
V
OUT1
Preset output,
V+ = 5.5V to 28V,
SKIP = V
CC
FB1 = V
CC
MAX1540 Main Output-Voltage
Accuracy (OUT1) (Note 2)
V
FB1
Adjustable output, V+ = 5.5V to 28V,
SKIP = V
CC
V
FB2 = GND
V
OUT2
Preset output,
V+ = 5.5V to 28V,
SKIP = V
CC
FB2 = V
CC
MAX1540 Secondary OutputVoltage Accuracy (OUT2)
(Note 2)
V
FB2
Adjustable output, V+ = 5.5V to 28V,
SKIP = V
CC
V
MAX1541 Main Feedback
Voltage Accuracy (FB1)
V
FB1
V+ = 4.5V to 28V,
SKIP = V
CC REFIN1 = REF
V
FB2 = GND
V
OUT2
Preset output,
V+ = 4.5V to 28V,
SKIP = V
CC
FB2 = V
CC
MAX1541 Secondary OutputVoltage Accuracy (OUT2)
(Note 2)
V
FB2
Adjustable output, V+ = 4.5V to 28V,
SKIP = V
CC
V
190
242
335
DH1 On-Time (Note 3) t
ON1
V+ = 15V,
V
OUT1
= 1.5V
491
ns
256
331
453
DH2 On-Time (Note 3) t
ON2
V+ = 15V,
V
OUT2
= 1.5V
679
ns
On-Time Tracking t
ON2
with respect to t
ON1
(Note 3)
152 %
Minimum Off-Time
)
(Note 3) 500 ns
LINEAR REGULATOR (LDO) (Note 1)
MAX1540 LDO Output-Voltage
Accuracy
ON1 = ON2 = GND,
V+ = 6V to 28V
V
SYMBOL
MIN MAX
t
OFF(MIN
V
LDOOUT
1.773 1.827
1.182 1.218
0.689 0.711
2.462 2.538
1.477 1.523
0.689 0.711
REFIN1 = 0.35 x REF 0.689 0.711
1.97 2.03
2.462 2.538
1.773 1.827
0.689 0.711
TON = G N D ( 620kH z) 149
TON = RE F ( 485kH z) 191
TON = op en ( 345kH z) 274
TON = V CC ( 235kH z) 402
TON = G N D ( 460kH z) 201
TON = RE F ( 355kH z) 260
TON = op en ( 255kH z) 371
TON = V CC ( 170kH z) 556
0 < I
0 < I
L D OOU T
< 10mA 4.85 5.10
LDOOUT
< 100m A 4.65 5.10
118
MAX1540/MAX1541
Dual Step-Down Controllers with Saturation
Protection, Dynamic Output, and Linear Regulator
_______________________________________________________________________________________ 9
ELECTRICAL CHARACTERISTICS (continued)
(V+ = 15V, VCC= VDD= ON1 = ON2 = 5V, SKIP = GND, LDOIN (MAX1541) = V+, TA= -40°C to +85°C, unless otherwise noted.)
(Note 4)
PARAMETER
CONDITIONS
UNITS
MAX1541 LDO Output-Voltage
Accuracy (Fixed V
LDOOUT
)
FBLDO = ON1 =
ON2 = GND,
V
MAX1541 LDO Feedback
Accuracy (Adjustable V
LDOOUT
)
FBLDO = LDOOUT,
ON1 = ON2 = GND,
V
LDOIN
= 4.5V to
28V
V
800
Dropout Voltage
MAX1541: V
LDOIN
- V
LDOOUT
,
I
LDOOUT
= 50mA
800
mV
REFERENCE (REF)
Reference Voltage V
REF
VCC = 4.5V to 5.5V, I
REF
= 0
V
REFIN1 Input Bias Current I
REFIN1
µA
FAULT DETECTION
Overvoltage Trip Threshold
With respect to error-comparator threshold,
OVP/UVP = V
CC
10 21 %
Output Undervoltage-Protection
Trip Threshold
With respect to error-comparator threshold,
OVP/UVP = V
CC
64 76 %
PGOOD_ Lower Trip Threshold
With respect to error-comparator threshold,
hysteresis = 1%
-14 -5 %
PGOOD_ Upper Trip Threshold
With respect to error-comparator threshold,
hysteresis = 1%
+5
%
PGOOD_ Output Low Voltage I
SINK
= 4mA 0.3 V
VCC Undervoltage-Lockout
Threshold
)
Rising edge, PWM disabled below this
level, hysteresis = 20mV
4.1 4.4 V
CURRENT LIMIT
CSP_ 0 2.7
Current-Limit Input Range
CSN_
V
Valley Current-Limit Threshold
(Fixed)
)
V
CSP
_ - V
CSN
_, ILIM_ = V
CC
40 60 mV
Valley Current-Limit Threshold
(Adjustable)
)
V
CSP
_ - V
CSN
_, V
ILIM
_ = 2.00V
240 mV
INPUTS AND OUTPUTS
Logic Input Threshold
ON1, ON2, SKIP, GATE, rising edge,
hysteresis = 225mV
1.2 2.2 V
LDOON Input Trip Level Rising edge, hysteresis = 250mV 1.2 1.3 V
High 1.9 2.1
Dual Mode Threshold Voltage
FB1 (MAX1540),
FB2 (MAX1540/MAX1541)
Low
V
SYMBOL
V
LDOOUT
V
FBLDO
V
= 6V to 28V
LDOIN
MAX1540: V+ - V
LDOOUT
0 < I
0 < I
0 < I
0 < I
, I
LDOOUT
L D OOU T
LDOOUT
L D OOU T
LDOOUT
< 10mA 4.85 5.10
< 100m A 4.65 5.10
< 10mA 1.212 1.275
< 100m A 1.175 1.275
= 50mA
MIN MAX
1.98 2.02
V
UVLO(VCC
V
LIM_ (VAL
V
LIM_ (VAL
-0.3 +28.0
160
0.05 0.15
0.05
+14
MAX1540/MAX1541
Dual Step-Down Controllers with Saturation
Protection, Dynamic Output, and Linear Regulator
10 ______________________________________________________________________________________
ELECTRICAL CHARACTERISTICS (continued)
(V+ = 15V, VCC= VDD= ON1 = ON2 = 5V, SKIP = GND, LDOIN (MAX1541) = V+, TA= -40°C to +85°C, unless otherwise noted.)
(Note 4)
PARAMETER
SYMBOL
CONDITIONS
MIN
MAX
UNITS
High
V
CC
-
Open
REF
Four-Level Input Logic Levels
TON, OVP/UVP, LSAT, SKIP,
FBLANK
Low 0.5
V
Note 1: For the MAX1540, the gate-driver input supply (VDD) is internally connected to the fixed 5V linear-regulator output (LDOOUT),
and the linear-regulator input supply (LDOIN) is internally connected to the battery voltage input (V+).
Note 2: When the inductor is in continuous conduction, the output voltage has a DC regulation level higher than the error-comparator
threshold by 50% of the ripple. In discontinuous conduction (SKIP = GND, light load), the output voltage has a DC regulation
level higher than the trip level by approximately 1.5% due to slope compensation.
Note 3: On-time and off-time specifications are measured from 50% point to 50% point at the DH_ pin with LX_ = GND, VBST_ = 5V,
and a 250pF capacitor connected from DH_ to LX_. Actual in-circuit times may differ due to MOSFET switching speeds.
Note 4: Specifications to -40°C are guaranteed by design, not production tested.
OUT2 EFFICIENCY vs. LOAD CURRENT
(V
OUT2
= 2.5V)
MAX1540 toc01
LOAD CURRENT (A)
EFFICIENCY (%)
10.1
55
60
65
70
75
80
85
90
95
100
50
0.01 10
SKIP = GND
SKIP = V
CC
VIN = 7V
VIN = 12V
VIN = 20V
2.5V OUTPUT VOLTAGE (OUT2)
vs. LOAD CURRENT
MAX1540 toc02
LOAD CURRENT (A)
OUTPUT VOLTAGE (V)
4321
2.49
2.50
2.51
2.52
2.53
2.54
2.55
2.48
05
SKIP = GND
SKIP = V
CC
OUT1 EFFICIENCY vs. LOAD CURRENT
(V
OUT1
= 1.0V)
MAX1540 toc03
LOAD CURRENT (A)
EFFICIENCY (%)
10.1
55
60
65
70
75
80
85
90
95
100
50
0.01 10
SKIP = GND
SKIP = V
CC
VIN = 7V
VIN = 12V
VIN = 20V
Typical Operating Characteristics
(MAX1541 Circuit of Figure 12, V
IN
= 12V, VDD= VCC= 5V, SKIP = GND, TON = REF, TA = +25°C, unless otherwise noted.)
0.4V
3.15 3.85
1.65 2.35
MAX1540/MAX1541
Dual Step-Down Controllers with Saturation
Protection, Dynamic Output, and Linear Regulator
______________________________________________________________________________________ 11
1.0V OUTPUT VOLTAGE (OUT1)
vs. LOAD CURRENT
MAX1540 toc04
LOAD CURRENT (A)
OUTPUT VOLTAGE (V)
431 2
0.99
1.00
1.01
1.02
0.98
05
SKIP = GND
SKIP = V
CC
OUT2 SWITCHING FREQUENCY
vs. LOAD CURRENT
(V
OUT2
= 2.5V)
MAX1540 toc05
LOAD CURRENT (A)
SWITCHING FREQUENCY (kHz)
4321
100
200
300
400
500
600
0
05
SKIP = GND
SKIP = V
CC
OUT1 SWITCHING FREQUENCY
vs. LOAD CURRENT
(V
OUT1
= 1.0V)
MAX1540 toc06
LOAD CURRENT (A)
SWITCHING FREQUENCY (kHz)
4321
100
200
300
400
500
600
0
05
SKIP = GND
SKIP = V
CC
SWITCHING FREQUENCY
vs. INPUT VOLTAGE
MAX1540 toc07
INPUT VOLTAGE (V)
SWITCHING FREQUENCY (kHz)
2420161284
250
300
350
400
450
200
028
4A LOAD
NO LOAD
2.5V OUTPUT
SKIP = V
CC
MAXIMUM OUTPUT CURRENT
vs. INPUT VOLTAGE
MAX1540 toc08
INPUT VOLTAGE (V)
MAXIMUM OUTPUT CURRENT (A)
242012 1684
4.2
4.4
4.6
4.8
5.0
5.2
5.4
5.6
5.8
6.0
4.0
028
2.5V OUTPUT
NO-LOAD SUPPLY CURRENT
vs. INPUT VOLTAGE
(FORCED-PWM OPERATION)
MAX1540 toc09
INPUT VOLTAGE (V)
SUPPLY CURRENT (mA)
2420161284
4
8
12
16
20
0
028
I
BIAS
I
IN
SKIP = ON1 = ON2 = V
CC
NO-LOAD SUPPLY CURRENT
vs. INPUT VOLTAGE
(PULSE-SKIPPING OPERATION)
MAX1540 toc10
INPUT VOLTAGE (V)
SUPPLY CURRENT (mA)
2420161284
0.2
0.4
0.6
0.8
1.0
1.2
1.4
0
028
SKIP = GND
ON1 = ON2 = V
CC
I
BIAS
I
IN
2.0V REFERENCE LOAD REGULATION
MAX1540 toc11
REFERENCE LOAD CURRENT (µA)
REFERENCE VOLTAGE DEVIATION (mV)
100
80
60
40
20
0
-3
-2
-1
0
1
2
3
4
-4
-20
REFERENCE DISTRIBUTION
MAX1540 toc12
REFERENCE VOLTAGE (V)
SAMPLE PERCENTAGE (%)
2.0052.0001.995
10
20
30
40
50
0
1.990 2.010
SAMPLE SIZE = 50
Typical Operating Characteristics (continued)
(MAX1541 Circuit of Figure 12, V
IN
= 12V, VDD= VCC= 5V, SKIP = GND, TON = REF, TA = +25°C, unless otherwise noted.)
MAX1540/MAX1541
Dual Step-Down Controllers with Saturation
Protection, Dynamic Output, and Linear Regulator
12 ______________________________________________________________________________________
Typical Operating Characteristics (continued)
(MAX1541 Circuit of Figure 12, V
IN
= 12V, VDD= VCC= 5V, SKIP = GND, TON = REF, TA = +25°C, unless otherwise noted.)
LINEAR-REGULATOR OUTPUT (LDOOUT)
vs. LOAD CURRENT
MAX1540 toc13
LDO LOAD CURRENT (mA)
LDO OUTPUT VOLTAGE (V)
806020 40
3.22
3.24
3.26
3.28
3.30
3.32
3.34
3.36
3.20
0 100
V
LDOIN
= 5V
V
LDOIN
= 12V
STARTUP WAVEFORM
(HEAVY LOAD)
MAX1540 toc14
3.3V
0
2.5V
0
B
D
C
A
400µs/div
4A
2A
0
0
A. ON2, 5V/div
B. INDUCTOR CURRENT,
2A/div
0.5Ω LOAD
C. OUT2, 2V/div
D. PGOOD2, 5V/div
STARTUP WAVEFORM
(LIGHT LOAD)
MAX1540 toc15
3.3V
0
2.5V
0
B
D
C
A
200µs/div
4A
2A
0
0
A. ON2, 5V/div
B. INDUCTOR CURRENT,
2A/div
100Ω LOAD
C. OUT2, 2V/div
D. PGOOD2, 5V/div
SHUTDOWN WAVEFORM
(DISCHARGE MODE DISABLED)
MAX1540 toc16
3.3V
0
5V
0
B
D
C
A
10ms/div
2.5V
0
0
0
A. ON2, 5V/div
B. OUT2, 2V/div
C. INDUCTOR CURRENT,
2A/div
100Ω LOAD, OVP/UVP = REF OR GND
D. DL2, 5V/div
E. PGOOD2, 5V/div
5V
E
MAX1540/MAX1541
Dual Step-Down Controllers with Saturation
Protection, Dynamic Output, and Linear Regulator
______________________________________________________________________________________ 13
Typical Operating Characteristics (continued)
(MAX1541 Circuit of Figure 12, V
IN
= 12V, VDD= VCC= 5V, SKIP = GND, TON = REF, TA = +25°C, unless otherwise noted.)
SHUTDOWN WAVEFORM
(DISCHARGE MODE ENABLED)
MAX1540 toc17
3.3V
0
5V
0
B
D
C
A
1ms/div
2.5V
0
0
0
A. ON2, 5V/div
B. OUT2, 2V/div
C. INDUCTOR CURRENT,
2A/div
100Ω LOAD, OVP/UVP = V
CC
OR OPEN
D. DL2, 5V/div
E. PGOOD2, 5V/div
5V
E
2.5V OUTPUT LOAD TRANSIENT
(FORCED PWM)
MAX1540 toc18
4A
0
4A
0
B
D
C
A
40µs/div
2.5V
2.4V
2.6V
A. I
OUT2
= 0 TO 4A, 5A/div
B. V
OUT2
= 2.5V, 100mV/div
SKIP = V
CC
C. INDUCTOR CURRENT, 5A/div
D. LX2, 10V/div
12V
0
2.5V OUTPUT LOAD TRANSIENT
(PULSE SKIPPING)
MAX1540 toc19
4A
0
4A
0
B
D
C
A
40µs/div
2.5V
2.4V
2.6V
A. I
OUT2
= 0.1A TO 4A, 5A/div
B. V
OUT2
= 2.5V, 100mV/div
SKIP = GND
C. INDUCTOR CURRENT, 5A/div
D. LX2, 10V/div
12V
0
LINEAR-REGULATOR
LOAD TRANSIENT
MAX1540 toc20
100mA
0
B
A
100µs/div
3.3V
3.2V
3.4V
A. I
LDOOUT
= 1mA TO 100mA, 50mA/div
B. V
LDOOUT
= 3.3V, 100mV/div
SKIP = GND
MAX1540/MAX1541
Dual Step-Down Controllers with Saturation
Protection, Dynamic Output, and Linear Regulator
14 ______________________________________________________________________________________
Typical Operating Characteristics (continued)
(MAX1541 Circuit of Figure 12, V
IN
= 12V, VDD= VCC= 5V, SKIP = GND, TON = REF, TA = +25°C, unless otherwise noted.)
LINEAR-REGULATOR
LINE TRANSIENT
MAX1540 toc21
20V
10V
20V
10V
3.8V
3.3V
2.8V
C
A
B
200µs/div
A. INPUT (V
IN
), 10V/div
B. LDOIN (10V TO 20V), 10V/div
C. LDOOUT (3.3V), 500mV/div
20mA LOAD
OUTPUT OVERLOAD
(UVP DISABLED)
MAX1540 toc22
20A
0
2.5V
10A
B
D
C
A
40µs/div
0
5A
0
5V
A. LOAD (0 TO 150mΩ), 10A/div
B. INDUCTOR CURRENT, 10A/div
OVP/UVP = OPEN OR GND
C. 2.5V OUTPUT, 2V/div
D. PGOOD2, 5V/div
0
OUTPUT OVERLOAD
(UVP ENABLED)
MAX1540 toc23
20A
0
2.5V
10A
B
D
C
A
20µs/div
0
5A
0
5V
A. LOAD (0 TO 150mΩ), 10A/div
B. INDUCTOR CURRENT, 10A/div
C. DL2, 5V/div
OVP/UVP = V
CC
OR REF
D. 2.5V OUTPUT, 2V/div
E. PGOOD2, 5V/div
E
0
5V
INDUCTOR-SATURATION PROTECTION
(LSAT DISABLED)
MAX1540 toc24
0
2.5V
B
D
C
A
20µs/div
5A
7.5A
A. I
OUT2
= 0 TO 5A, 5A/div
B. 2.5V OUTPUT, 200mV/div
LSAT = GND, L = 3.3µH 3.5A
C. ILIM, 100mV/div
D. INDUCTOR CURRENT, 5A/div
0.67V
0
MAX1540/MAX1541
Dual Step-Down Controllers with Saturation
Protection, Dynamic Output, and Linear Regulator
______________________________________________________________________________________ 15
Typical Operating Characteristics (continued)
(MAX1541 Circuit of Figure 12, V
IN
= 12V, VDD= VCC= 5V, SKIP = GND, TON = REF, TA = +25°C, unless otherwise noted.)
INDUCTOR-SATURATION PROTECTION
(∆V
ILIM
= 200mV)
MAX1540 toc25
0
2.5V
B
D
C
A
20µs/div
5A
7.5A
A. I
OUT2
= 0 TO 5A, 5A/div
B. 2.5V OUTPUT, 200mV/div
LSAT = REF, L = 3.3µH 3.5A
C. ILIM, 200mV/div
D. INDUCTOR CURRENT, 5A/div
0.67V
0
0.47V
INDUCTOR-SATURATION PROTECTION
(∆V
ILIM
= 400mV)
MAX1540 toc26
0
2.5V
1.5V
B
D
C
A
20µs/div
5A
5A
A. I
OUT2
= 0 TO 5A, 5A/div
B. 2.5V OUTPUT, 1V/div
C. PGOOD, 5V/div
LSAT = REF, L = 3.3µH 3.5A
D. ILIM, 400mV/div
E. INDUCTOR CURRENT, 5A/div
5V
0
0.67V
E
0.27V
MAX1541
DYNAMIC OUTPUT-VOLTAGE TRANSITION
(C
REFIN1
= 100pF)
MAX1540 toc27
-5A
1.5V
B
D
C
A
40µs/div
5A
5A
A. GATE, 5V/div
B. OUT1 (1.0V TO 1.5V), 0.5V/div
C. REFIN1, 0.5V/div
200mA LOAD, SKIP = GND
D. PGOOD1, 5V/div
E. INDUCTOR CURRENT, 5A/div
1.5V
0
1V
E
5V
0
MAX1541
DYNAMIC OUTPUT-VOLTAGE TRANSITION
(C
REFIN1
= 1nF)
MAX1540 toc28
-5A
1.5V
B
D
C
A
100µs/div
5A
5A
A. GATE, 5V/div
B. OUT1 (1.0V TO 1.5V), 0.5V/div
C. REFIN1, 0.5V/div
200mA LOAD, SKIP = GND
D. PGOOD1, 5V/div
E. INDUCTOR CURRENT, 5A/div
1.5V
0
1V
E
5V
0
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