19-3507; Rev 1; 3/06
KIT
ATION
EVALU
BLE
AVAILA
Low-Voltage, Internal Switch,
Step-Down/DDR Regulator
General Description
Features
♦
♦
♦
♦
♦
♦
Dual 40mΩ Internal n-Channel MOSFETs
Integrated Boost Switch
+1.3V to +3.6V Input Voltage Range
1% V
OUT
Accuracy Over Line and Load
1MHz Maximum Switching Frequency
DDR Termination Regulator (DDR Mode)
Tracking Output Voltage
Source/Sink Pulse Skipping
±5mA Reference Buffer
Output Voltage (Non-DDR Mode)
+2.5V, +1.8V, or +1.5V Pin Selectable
+0.5V to +2.7V Adjustable
1.1V ±0.75% Reference Output
Adjustable Soft-Start Inrush Current Limiting
< 1µA (typ) Shutdown Supply Current
< 800µA (max) Operating Supply Current
Selectable Pulse-Skipping Operation at Light Loads
Positive and Negative Current Limit
Power-Good Window Comparator
Output Short-Circuit Protection
MAX1515
The MAX1515 constant-off-time, pulse-width-modulated
(PWM) source/sink step-down DC-DC converter is opti-
mized for use in low-voltage active-termination power
rails or chipset power supplies in notebook and sub-
notebook computers. This device features dual internal
n-channel MOSFET power switches for high efficiency
and reduced component count. External Schottky
diodes are not required. An integrated boost switch
eliminates the need for an external boost diode. The
internal 40mΩ NMOS power switches easily source and
sink continuous load currents up to 3A. The MAX1515
produces an adjustable output from +0.5V to +2.7V
and achieves efficiencies as high as 95%.
The MAX1515 can be configured as a DDR regulator,
producing an output that is exactly half the memory
supply rail. The input of the power stage can be taken
from the memory supply rail itself, resulting in an effi-
cient power supply that returns the energy to the rail
from which it was sourced. The MAX1515 includes a
reference buffer that provides ±5mA of drive current.
The MAX1515 uses a unique current-mode, constant-
off-time, PWM control scheme. A selectable pulse-skip-
ping mode maintains high efficiency during light-load
operation, yet still sources and sinks current on
demand. The MAX1515 can also be operated in fixed-
PWM mode for low output ripple. The programmable
constant-off-time architecture sets switching frequen-
cies up to 1MHz, which allows the user to optimize per-
formance trade-offs between efficiency, output
switching noise, component size, and cost. The
MAX1515 features an adjustable soft-start to limit surge
currents during startup and a low-power shutdown
mode to disconnect the input from the output and
reduce supply current below 1µA. The MAX1515 is
available in a 24-pin thin QFN package with an
exposed backside pad.
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Ordering Information
PART
MAX1515ETG
MAX1515ETG+
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
PIN-
PACKAGE
24 Thin QFN
4mm x 4mm
24 Thin QFN
4mm x 4mm
PKG CODE
T2444-4
T2444-4
+Denotes
lead-free package.
Minimal Operating Circuit
V
BIAS
(3.0V TO 3.6V)
V
IN
(1.3V TO 3.6V)
IN
V
DD
BST
Applications
Notebook DDR Memory Termination
Active-Termination Buses
Chipset/Graphics Processor Supplies
V
CC
COMP
PGOOD
SHDN
MODE
SKIP
REF
V
DDQ
(2.5V OR 1.8V)
REFIN
SS
TOFF
FBSEL0
FBSEL1
V
REFOUT
= V
TTR
REFOUT
MAX1515
V
OUT
= V
TT
LX
FB
PGND
GND
Pin Configuration appears at end of data sheet.
________________________________________________________________
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.
Low-Voltage, Internal Switch,
Step-Down/DDR Regulator
MAX1515
ABSOLUTE MAXIMUM RATINGS
V
CC
, V
DD
, LX,
SHDN
to GND ...................................-0.3V to +4V
MODE, IC to GND ....................................................-0.3V to +4V
COMP, FB, REF, REFIN, REFOUT, PGOOD
to GND.........................................................-0.3V to (V
CC
+ 0.3V)
FBSEL0, FBSEL1, TOFF,
SKIP,
SS to GND....-0.3V to (V
CC
+ 0.3V)
V
DD
to V
CC
...........................................................-0.3V to + 0.3V
IN to V
DD
....................................................-0.3V to (V
DD
+ 0.3V)
PGND to GND ...................................................... -0.3V to +0.3V
LX to BST................................................................. -4V to +0.3V
BST to GND .......................................................... -0.3V to +8.0V
LX Current (Note 1).............................................................±4.7A
REF Short Circuit to GND ...........................................Continuous
REFOUT Short Circuit to GND....................................Continuous
Continuous Power Dissipation (T
A
= +70°C)
24-Pin Thin QFN (derate 20.8mW/°C above +70°C;
part mounted on 1in
2
of 1oz copper)........................1667mW
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:
LX has clamp diodes to PGND and IN. If continuous current is applied through these diodes, thermal limits must be observed.
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
= +3.3V, V
CC
= V
DD
=
SHDN
= MODE = +3.3V, V
REFIN
= V
REF
,
SKIP
= GND,
T
A
= 0°C to +85°C,
unless oth-
erwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
PWM CONTROLLER
Input Voltage Range
Output Adjust Range
V
FB
-
V
REFIN
V
IN
V
CC
, V
DD
V
OUT
≤
V
IN
V
IN
= +3.3V, I
LOAD
= 0,
MODE = V
CC
T
A
= +25°C
to +85°C
T
A
= 0°C to
+85°C
1.3
3.0
0.5
-3
-4
2.463
2.450
1.782
1.773
1.477
1.470
0.492
0.490
0
0
2.5
2.5
1.800
1.800
1.500
1.500
0.500
0.500
0.1
3.6
3.6
2.7
+3
mV
+4
2.537
2.550
1.827
1.836
V
1.523
1.530
0.508
0.510
%
V
V
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
T
A
= +25°C
FBSEL0 = V
CC
, to +85°C
FBSEL1 = V
CC
,
T
A
= 0°C to
REFIN = REF
+85°C
T
A
= +25°C
FBSEL0 = V
CC
, to +85°C
FBSEL1 = GND,
T
A
= 0°C to
REFIN = REF
V
IN
= +3.3V,
+85°C
I
LOAD
= 0,
T
A
= +25°C
MODE = low
FBSEL0=GND to +85°C
FBSEL1=V
CC
T
A
= 0°C to
REFIN=REF
+85°C
FBSEL0=GND
FBSEL1=GND
REFIN=0.5V
T
A
= +25°C
to +85°C
T
A
= 0°C to
+85°C
Feedback Voltage Accuracy
V
FB
Feedback Load-Regulation Error
V
IN
= +1.3V to +3.6V, I
LOAD
= 0 to 3A,
SKIP
= V
CC
2
_______________________________________________________________________________________
Low-Voltage, Internal Switch,
Step-Down/DDR Regulator
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, V
IN
= +3.3V, V
CC
= V
DD
=
SHDN
= MODE = +3.3V, V
REFIN
= V
REF
,
SKIP
= GND,
T
A
= 0°C to +85°C,
unless oth-
erwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
Sink-Mode Detect Threshold
Source-Mode Detect Threshold
MOSFET On-Resistance
Switching Frequency
Maximum Output Current
Current-Limit Threshold
SYMBOL
V
FB
-
V
REFIN
V
FB
-
V
REFIN
R
NMOS
f
SW
I
OUT(RMS)
I
LIMIT_P
I
LIMIT_N
Pulse-Skipping Current Threshold
I
SKIP_P
I
ZX_P
I
ZX_N
FB Input Bias Current
Off-Time
t
OFF
CONDITIONS
MODE = V
CC
, V
REFIN
= +0.5V to +1.5V
MODE = V
CC
, V
REFIN
= +0.5V to +1.5V
V
CC
= V
DD
= V
IN
= +3.3V, I
LOAD
= 0.5A
(Note 2)
(Note 3)
V
IN
= +3.3V, MODE = GND or V
CC
,
positive or sourcing mode
MODE = V
CC
, negative or sinking mode
V
IN
= +3.3V, MODE = GND or V
CC
, positive
or sourcing mode
V
IN
= +3.3V, MODE = GND or V
CC
, positive
or sourcing mode
MODE = V
CC
, negative or sinking mode
FB = 1.01 x V
TARGET
(Note 4)
V
FB
> 0.3 x V
TARGET
(Note 4)
R
TOFF
= 33.2kΩ
R
TOFF
= 110kΩ
R
TOFF
= 499kΩ
Extended Off-Time
Minimum On-Time
Maximum On-Time
SS Source Current
SS Sink Current
t
OFF(EXT)
t
ON(MIN)
t
ON(MAX)
I
SS(SRC)
I
SS(SNK)
MODE = GND,
FBSEL0 = GND,
FBSEL1 = GND,
V
FB
= 1.01 x
V
TARGET
MODE = V
CC
,
V
FB
= V
TARGET
I
CC
+ I
DD
+ I
IN
I
IN
I
LX
SHDN
= MODE = GND, LX = 0V or 3.3V
SHDN
= MODE = GND, LX = 0V
SHDN
= MODE = GND, LX = 3.3V
V
FB
< 0.3 x V
TARGET
(Notes 2, 4)
(Note 2)
5
3.50
100
-50
0.270
0.85
3.8
0.34
1.00
4.5
4x
t
OFF
180
11
5.25
6.75
0.5
3.3
3.60
4.2
-3.0
0.8
200
-350
+50
0.405
1.15
5.2
µs
ns
µs
µA
µA
µs
nA
1.1
A
4.85
MIN
+18
-32
0.04
TYP
MAX
+32
-18
0.10
1
UNITS
mV
mV
Ω
MHz
A
A
MAX1515
Zero Cross Current Threshold
mA
450
800
µA
No-Load Supply Current
I
CC
+ I
DD
+ I
IN
V
IN
= 3.3V
(not switching) (Note 4)
700
0.2
0.2
0.1
1200
20
20
20
µA
Shutdown Supply Currents
_______________________________________________________________________________________
3
Low-Voltage, Internal Switch,
Step-Down/DDR Regulator
MAX1515
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, V
IN
= +3.3V, V
CC
= V
DD
=
SHDN
= MODE = +3.3V, V
REFIN
= V
REF
,
SKIP
= GND,
T
A
= 0°C to +85°C,
unless oth-
erwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
REFERENCE
T
A
= +25°C to
+85°C
Reference Voltage
V
REF
V
CC
= +3.0V to +3.6V
T
A
= 0°C to
+85°C
1.0923
1.0907
1.100
1.100
1.1077
V
1.1094
10
0.5
I
REFOUT
= -1mA
to +1mA
I
REFOUT
= -5mA
to +5mA
-10
-20
-50
+165
2.5
-13
+7
2.7
-10
+10
10
0.1
1
2.9
-7
+13
1.5
+10
mV
V
REFIN
= +0.5V to +1.5V
V
REFIN
= 1.1V
Rising, hysteresis = 15°C
No load, falling edge, hysteresis = 1%
No load, rising edge, hysteresis = 1%
t
PGOOD
FB forced 2% beyond PGOOD trip
threshold
I
SINK
= 1mA
High state, forced to 3.6V; V
CC
= V
DD
= 3.6V
+20
+50
nA
°C
V
%
%
µs
V
µA
mV
V
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Reference Load Regulation
REFIN Input Voltage Range
V
REFIN
V
REFIN
-
V
REFOUT
I
REFIN
T
SHDN
I
REF
= -1µA to +50µA
V
CC
= +3.0V to +3.6V
V
REFIN
= +0.5V to +1.5V
REFOUT Output Accuracy
REFIN Input Bias Current
FAULT DETECTION
Thermal Shutdown
Undervoltage-Lockout Threshold
PGOOD Trip Threshold (Lower)
PGOOD Trip Threshold (Upper)
PGOOD Propagation Delay
PGOOD Output Low Voltage
PGOOD Leakage Current
Condition
INPUTS AND OUTPUTS
Logic Input High Voltage
Logic Input Low Voltage
Logic Input Current
V
CC(UVLO)
V
CC
rising, 2% falling-edge hysteresis
SKIP, SHDN,
MODE, FBSEL0, FBSEL1
SKIP, SHDN,
MODE, FBSEL0, FBSEL1
SKIP, SHDN,
MODE, FBSEL0, FBSEL1
2.0
0.8
-0.5
+0.5
V
V
µA
4
_______________________________________________________________________________________
Low-Voltage, Internal Switch,
Step-Down/DDR Regulator
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 1, V
IN
= +3.3V, V
CC
= V
DD
=
SHDN
= MODE = +3.3V, V
REFIN
= V
REF
,
SKIP
= GND,
T
A
= -40°C to +85°C,
unless
otherwise noted. Note 5)
PARAMETER
PWM CONTROLLER
Input Voltage Range
Output Adjust Range
V
FB
-
V
REFIN
V
IN
V
CC
, V
DD
V
OUT
≤
V
IN
V
IN
= +3.3V, I
LOAD
= 0, MODE = V
CC
FBSEL0 = V
CC
,
FBSEL1 = V
CC
,
REFIN = REF
FBSEL0 = V
CC
,
FBSEL1 = GND,
REFIN = REF
FBSEL0 = GND,
FBSEL1 = V
CC
,
REFIN = REF
FBSEL0 = GND,
FBSEL1 = GND,
REFIN = 0.5V
Sink-Mode Detect Threshold
Source-Mode Detect Threshold
nFET On-Resistance
Switching Frequency
Current-Limit Threshold
Pulse-Skipping Current Threshold
V
FB
-
V
REFIN
V
FB
-
V
REFIN
R
NMOS
f
SW
I
LIMIT_P
I
SKIP_P
MODE = V
CC
, V
REFIN
= +0.5V to +1.5V
MODE = V
CC
, V
REFIN
= +0.5V to +1.5V
V
CC
= V
DD
= V
IN
= +3.3V, I
LOAD
= 0.5A
(Note 2)
V
IN
= +3.3V, MODE = GND or V
CC
,
positive or sourcing mode
V
IN
= +3.3V, MODE = GND or V
CC
,
positive or sourcing mode
V
FB
> 0.3 x V
TARGET
(Note 4)
R
TOFF
= 33.2kΩ
R
TOFF
= 110kΩ
R
TOFF
= 499kΩ
Maximum On-Time
SS Source Current
SS Sink Current
t
ON(MAX)
I
SS(SRC)
I
SS(SNK)
3.35
0.4
0.250
0.8
3.8
5
3
100
7
1.3
3.0
0.5
-5
3.6
3.6
V
CC
+5
V
V
mV
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
MAX1515
2.438
2.562
Feedback Voltage Accuracy
V
FB
V
IN
= +3.3V, I
LOAD
= 0,
MODE = low
1.755
1.845
V
1.463
1.538
0.487
0.513
+15
-35
+35
-15
0.10
1
5.05
1.2
0.425
1.2
5.2
mV
mV
Ω
MHz
A
A
Off-Time
t
OFF
µs
µs
µA
µA
_______________________________________________________________________________________
5
Microchip MCU
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