MAX17250ATD [MAXIM]
2.7V to 18V Input, Boost Converter with 0.1μA True Shutdown, Short-Circuit Protection and Selectable Input Current Limit;
| 型号： | MAX17250ATD |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | 2.7V to 18V Input, Boost Converter with 0.1μA True Shutdown, Short-Circuit Protection and Selectable Input Current Limit |
| 文件： | 总13页 (文件大小：1027K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
EVALUATION KIT AVAILABLE
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MAX17250
2.7V to 18V Input, Boost Converter with 0.1μA
True Shutdown, Short-Circuit Protection
and Selectable Input Current Limit
General Description
Benefits and Features
● Input Voltage Range 2.7V to 18V
TheMAX17250DC-DCboostconverterisahigh-efficiency,
low quiescent current, synchronous boost (step-up)
converter with True Shutdown™, programmable input
current limit, and short-circuit protection. The MAX17250
has a wide input voltage range of 2.7V to 18V and
generates an output voltage of 3V to 18V. The MAX17250
has a maximum on-time of 800ns and implements three
modes of operation. The first mode of operation is a
soft-start mode at power-up. The second mode of
operation is normal operation and utilizes a fixed on-time/
minimum off-time Pulse Frequency Modulation (PFM)
architecture that uses only 60μA (typ) quiescent
current due to the converter switching only when needed.
The last mode is True Shutdown, where the output is
completely disconnected from the input, and the battery
drain is minimized to 0.1μA (typ) shutdown current. The
MAX17250 is available in a compact, 12-bump, 1.72mm
x 1.49mm WLP or a 14-pin, 3mm x 3mm TDFN package.
• 1 or 2 Cell Li-ion Batteries
● Output Voltage Range 3V to 18V, > V
● Integrated Power FETs
IN
● Selectable Input Peak Current Limit (ISET)
• 3.5A, 2.7A, or 1.85A
● 93% Efficiency
● Low Power
• 0.1μA True Shutdown Current
• 60μA Quiescent Current
● Protection
• True Shutdown Prevents Current Flowing Between
Input and Output
• Soft-Start Inrush Protection
• Short-Circuit Protection
• Overtemperature Protection
• -40°C to +125°C Operation
Applications
● Digital Cameras
● Battery Powered Internet of Things (IoT) Device
● 1 or 2 Cell Li-ion Battery Applications
● Display Supply
Ordering Information appears at end of data sheet.
● Buzzer/Alarm Driver
True Shutdown is a trademark of Maxim Integrated Products.
Typical Application Circuit
L
3.0V to 8.4V
2.2µH
0.1µF
12V
OUT
IN
LX
IN
BST
OUT
PVH
CIN
2x10µF
COUT
10µF
CPVH
2x22µF
Rz
1kΩ
4.7nF
EN
GND
EN MAX17250
R1
84.5kΩ
VL
ISET
FB
VL
2.2µF
R2
10kΩ
AGND
PGND
19-100359; Rev 2; 10/19
MAX17250
2.7V to 18V Input, Boost Converter with 0.1μA
True Shutdown, Short-Circuit Protection
and Selectable Input Current Limit
Absolute Maximum Ratings
IN, LX, OUT, PVH to AGND...................................-0.3V to +22V
BST to LX.................................................................-0.3V to +6V
EN, ISET, FB, VL to AGND......................................-0.3V to +6V
PGND to AGND.....................................................-0.3V to +0.3V
TDFN Continuous Power Dissipation
(T = +70°C, derate 24.4mW/°C above +70°C.).....1951.2mW
A
Operating Temperature Range.......................... -40°C to +125°C
Junction Temperature.......................................................+150°C
Storage Temperature Range............................. -65°C to +150°C
Lead Temperature (soldering, 10 seconds)......................+300°C
Soldering Temperature (reflow)........................................+260°C
WLP LX RMS Current.............................-3.2A
TDFN LX RMS Current.......................-2.58A
Short-Circuit Between OUT and GND........................Continuous
WLP Continuous Power Dissipation
to +3.2A
RMS
RMS
to +2.58A
RMS
RMS
(T = +70°C, derate 13.7mW/°C above +70°C.)........1096mW
A
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.
Package Information
14-TDFN
Package Code
T1433+2C
21-0137
90-0063
Outline Number
Land Pattern Number
Thermal Resistance, Single-Layer Board:
Junction to Ambient (θ
)
54°C/W
8°C/W
JA
Junction to Case (θ
)
JC
Thermal Resistance, Four-Layer Board:
Junction to Ambient (θ
)
41°C/W
8°C/W
JA
Junction to Case (θ
)
JC
12-WLP
Package Code
Outline Number
N121B1+1
21-100158
Land Pattern Number
Thermal Resistance, Four-Layer Board:
Junction to Ambient (θ
Refer to Application Note 1891
)
72.82°C/W
N/A
JA
Junction to Case (θ
)
JC
For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a “+”,
“#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing
pertains to the package regardless of RoHS status.
Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-layer board.
For detailed information on package thermal considerations, refer to www.maximintegrated.com/thermal-tutorial.
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MAX17250
2.7V to 18V Input, Boost Converter with 0.1μA
True Shutdown, Short-Circuit Protection
and Selectable Input Current Limit
Electrical Characteristics
(V = 7.2V, V
= V
= 10V, V = 5V, T = -40°C to +125°C, typical values are at T = +25°C, unless otherwise noted.) (Note 1)
IN
PVH
OUT
EN
A
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
18
UNITS
Input Voltage Range
V
2.7
V
IN
T
T
= 25°C
60
80
Quiescent Supply
Current
Not switching, 105%
A
A
I
μA
μA
Q
of V
= -40°C to 125°C
95
OUT_TARGET,
V
V
= V
= 0V,
EN
OUT
Shutdown Current
I
T
= 25°C
<0.001
1
SD
A
= 7.2V
PVH
Output Voltage Range
FB Accuracy
V
V
< V
OUT_TARGET
3
18
V
V
OUT
IN
ACC
V
falling, when LX starts switching
1.235
1.25
2.6
1.265
FB
Input Undervoltage
Threshold
V
Rising, hysteresis typical 100mV
2.68
V
UVLO
PEAK
ISET = Open (Note 2)
ISET = AGND (Note 2)
ISET = VL (Note 2)
1.48
2.16
2.8
1.85
2.7
2.31
3.45
4.55
Inductor Peak Current
Limit
I
A
3.5
LX Switch Maximum
On-Time
t
V
V
= 1.2V, I
= 0A
OUT
640
160
800
960
260
ns
ON
FB
FB
LX Switch Minimum
Off-Time
t
= 1.2V
200
9
ns
OFF
Startup Slew Rate
t
Using Typical Application Circuit
V/ms
ST_SR
V
= V
= 18V, V
= V
= 0V,
= 0V,
LX
PVH
EN
OUT
9
1000
T = 25°C
A
LX Leakage Current
I
nA
LX_LEAK
V
= V
PVH
= 125°C
= 18V, V
= V
LX
EN
OUT
570
3.4
T
A
Output Short-Circuit
Current Limit
I
V
= V = 5V
PVH
2.6
4.25
A
OUT_SHORT
IN
ISET = OPEN
ISET = AGND
175
120
95
380
260
200
N-Channel On-
Resistance
R
R
mΩ
mΩ
mA
DS(ON)
DS(ON)
ISET = V
L
Load Switch-On
Resistance
V
= V
= 5V
250
520
IN
PVH
ISET = OPEN (Note 2)
ISET = AGND (Note 2)
90
130
170
1.2
1.7
2.3
Synchronous Rectifier
Zero Crossing
I
ZX
ISET = V (Note 2)
L
ISET = OPEN (Note 2)
ISET = AGND (Note 2)
Synchronous Rectifier
Valley Current Crossing
I
A
V
VX
ISET = V (Note 2)
L
V
V
V
= 2.7V to 18V
= 2.7V to 18V
0.4
Enable Voltage
Threshold
IL
IN
IN
V
1.5V
IH
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MAX17250
2.7V to 18V Input, Boost Converter with 0.1μA
True Shutdown, Short-Circuit Protection
and Selectable Input Current Limit
Electrical Characteristics (continued)
(V = 7.2V, V
= V
= 10V, V = 5V, T = -40°C to +125°C, typical values are at T = +25°C, unless otherwise noted.) (Note 1)
IN
PVH
OUT
EN
A
A
PARAMETER
SYMBOL
CONDITIONS
≤ 5.5V, T = 25°C, V
MIN
TYP
MAX
UNITS
0V ≤ V
= 0V, V
=
EN
A
EN
IN
V
V
V
= V
= V
= 7.2V, V
= V = 0V,
LX
PVH
BST
OUT FB
-1
+0.45
+1
= 5.5V, V = V = 7.2V, V
= V
BST
=
=
EN
IN
LX
PVH
= 10V, V = 1.3V
OUT
FB
Enable Input Leakage
I
µA
EN_LK
0V ≤ V
≤ 5.5V, T = 125°C, V
= 0V, V
EN
A
EN IN
V
V
V
= V
= V
= 7.2V, V
= V = 0V,
LX
PVH
BST
OUT FB
0.65
= 5.5V, V = V = 7.2V, V
= V
=
EN
IN
LX
PVH
BST
= 10V, V = 1.3V
OUT
FB
T
T
= 25°C
-100
-1
+10
60
+100
+1
A
FB Leakage
I
V
= 1.25V,
nA
µA
FB_LK
FB
= 125°C
A
0V ≤ V
0V ≤ V
≤ V , T = 25°C
+0.0005
0.001
ISET
L
A
ISET Input Leakage
ISET Maximum Tie-
I
I
SET_LK
≤ V , T = 125°C
ISET
L
A
High (to V )/Tie-Low
200
Ω
L
(to GND) Resistance
VL Voltage
VL
No load
3.29
-1
3.38
3.47
+1
V
<
V
= V
= 18V, V = 0V, T = 25°C
EN A
BST
PVH
PVH
+0.001
BST Leakage
OUT Leakage
µA
µA
BST_LK
V
V
V
V
= V
= 18V, V
= 0V, T = 125°C
0.02
+0.002
0.25
BST
PVH
PVH
PVH
EN
OUT
OUT
A
= 18V, V
= 18V, V
= 18V, V
= V
= V
= 0V, T = 25°C
-1
-1
+1
+1
EN
EN
EN
A
I
OUT_LK
= 0V, T = 125°C
A
= V = VOUT = 0V,
LX
+0.015
0.5
T = 25°C
A
PVH Leakage
I
µA
PVH_LK
V
= 18V, V
= V = VOUT = 0V,
PVH
EN LX
T = 125°C
A
Overtemperature
Lockout Threshold
T rising, 15°C typical hysteresis
J
165
°C
V
Rising
Falling
2.03
2
2.185
2.145
2.34
2.3
VL_UVLO Voltage
VL_UVLO
Note 1: Limits are 100% production tested at T = +25°C. Limits over the operating temperature range are guaranteed through
A
correlation using statistical quality control (SQC) methods.
Note 2: This is a static measurement. The actual dynamic threshold depends upon V , V
and the inductor due to propagation
IN OUT
delays.
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MAX17250
2.7V to 18V Input, Boost Converter with 0.1μA
True Shutdown, Short-Circuit Protection
and Selectable Input Current Limit
Typical Operating Characteristics
(MAX17250ANC+, V = 7.2V, V
= 12V, C = 2 x 10µF, C
= 10µF, C
= 2 x 22µF, C = 2.2µF, T = 25°C, unless otherwise
IN
OUT
IN
OUT
PVH
VL
A
noted.)
TOTAL SYSTEM SHUTDOWN CURRENT
vs. TEMPERATURE
VIN CURRENT vs. TEMPERATURE
VIN CURRENT vs. INPUT VOLTAGE
toc01
toc03
toc02
340
700
600
500
400
300
200
EN = 0V
EN = VIN, VOUT REGULATED TO
12V, 125µA LOAD
EN = 1.8V, VOUT REGULATED TO
12V, 125µA LOAD
330
320
310
300
290
280
270
260
5050
4050
3050
2050
1050
50
2.7 3.7 4.7 5.7 6.7 7.7 8.7 9.7 10.7 11.7
-50
-25
0
25
50
75
100 125
-40 -20
0
20 40 60 80 100 120
TEMPERATURE (ºC)
TEMPERATURE (ºC)
V
(V)
IN
EFFICIENCY vs. LOAD CURRENT
(VOUT = 12V)
MAXIMUM OUTPUT CURRENT
vs. INPUT VOLTAGE
VIN CURRENT vs. INPUT VOLTAGE
toc06
toc04
toc05
100
95
90
85
80
75
70
65
60
1200
1000
800
600
400
200
0
400
350
300
250
200
VIN = 8.4V WLP
VIN = 7.2V TDFN
VOUT = 12V , L = 2.2µH
EN = 1.8V, VOUT REGULATED TO 5V,
125µA LOAD
VOUT = 5V , L = 1.0µH
VIN = 5.4V WLP
VIN = 7.2V WLP
VOUT = 18V , L = 3.3µH
1
10
100
1000
2.7
3.7
4.7
5.7
6.7
7.7
8.7
2.7
3.1
3.5
3.9
(V)
4.3
4.7
LOAD CURRENT (mA)
VIN (V)
V
IN
EFFICIENCY vs. LOAD CURRENT
(VOUT = 5V)
EFFICIENCY vs. LOAD CURRENT
(VOUT = 14V)
SWITCHING FREQUENCY
vs. LOAD CURRENT
toc08
toc07
toc09
95
90
85
80
75
70
65
60
100
90
80
70
60
50
40
VIN = 3.3V TDFN
VIN = 4.2V WLP
VIN = 8.4V WLP
VIN = 7.2V TDFN
1000.00
100.00
10.00
1.00
VIN = 3.3V, VOUT = 5V
VIN = 7.2V WLP
VIN = 3.3V WLP
VIN = 2.7V WLP
VIN = 5.4V WLP
VIN = 7.2V, VOUT = 12V
0.10
1
10
100
1000
0.01
1
10
100
1000
10
1000
100000
LOAD CURRENT (mA)
LOAD CURRENT (mA)
LOAD CURRENT (µA)
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MAX17250
2.7V to 18V Input, Boost Converter with 0.1μA
True Shutdown, Short-Circuit Protection
and Selectable Input Current Limit
Typical Operating Characteristics (continued)
(MAX17250ANC+, V = 7.2V, V
= 12V, C = 2 x 10µF, C
= 10µF, C
= 2 x 22µF, C = 2.2µF, T = 25°C, unless otherwise
IN
OUT
IN
OUT
PVH
VL
A
noted.)
STARTUP
LOAD TRANSIENT
POWER DOWN
toc12
toc11
toc10
VOUT
30mV/div
(AC-
1V/div
4V/div
COUPLED)
EN
EN
1V/div
4V/div
2A/div
ILX
VOUT
VOUT
500mA/div
IOUT
6V/div
VLX
ILX
1A/div
ILX
1A/div
20µSec/div
1mSec/div
VIN = 5.4V, VOUT = 12V, IOUT = 0A
100µSec/div
VIN = 7.2V, VOUT = 12V, IOUT = 0A
VIN = 7.2V, VOUT = 12V, IOUT = 0 TO 500mA
HEAVY LOAD
SWITCHING WAVEFORM
MEDIUM LOAD
SWITCHING WAVEFORM
NO LOAD
SWITCHING WAVEFORM
toc15
toc14
toc13
VOUT
50mV/div
(AC-
VOUT
100mV/div
(AC-
COUPLED)
COUPLED)
VOUT
100mV/div
(AC-
COUPLED)
ILX
1A/div
ILX
1A/div
ILX
1A/div
6V/div
VLX
6V/div
VLX
6V/div
VLX
IOUT
500mA/div
300mA/div
IOUT
5mSec/div
2µSec/div
5µSec/div
VIN = 7.2V, VOUT = 12V, IOUT = 0A
VIN = 7.2V, VOUT = 12V, IOUT = 0.76A
VIN = 7.2,VOUT = 12V, IOUT = 300mA
LINE TRANSIENT
SHORT AT OUTPUT
toc16
toc17
50mV/div
(AC-
COUPLED)
VOUT
ILX
VOUT
5V/div
3A/div
1V/div
ILX
VIN
5V/div)
1A/div
4A/div
5V/div
IOUT
VLX
6V/div
VIN
200µSec/div
50µSec/div
VIN = 7.2V, VOUT = 12V, IOUT = SHORT to GND
VIN = 5.4V TO 8.4V, VOUT = 12V, IOUT = 680mA
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MAX17250
2.7V to 18V Input, Boost Converter with 0.1μA
True Shutdown, Short-Circuit Protection
and Selectable Input Current Limit
Pin Configurations
TOP VIEW
TOP VIEW
1
2
3
4
PGND
PGND
LX
V
1
2
3
4
5
6
7
14
13
12
11
10
9
L
+
+
AGND
BST
OUT
PVH
IN
EN
A
B
C
FB
LX
FB
ISET
LX
LX
ISET
AGND
BST
PVH
PVH
OUT
*EP
8
IN
EN
PGND
V
L
TDFN
*CONNECT EXPOSED PAD TO GND
WLP
Pin Description
PIN
NAME
FUNCTION
WLP
A1
TDFN
6
7
AGND
BST
Analog Ground.
A2
Boost Flying Capacitor Connection. Connect a 0.1µF cap from BST to LX.
Output. Connect, at least, a 10µF capacitor from OUT to PGND.
Load Switch Gate Driver Supply. Connect two 22µF capacitors to PGND.
A3
8
OUT
PVH
A4
9, 10
Feedback. Connect to the center point of a resistor-divider from OUT to AGND to set the
target output voltage.
B1
4
FB
Inductor Peak Current Limit Select. Set the inductor peak current limit by connecting this pin
B2
5
ISET
LX
to either V (I
= 3.5A), AGND (I
= 2.7A) or leave unconnected (I
= 1.85A).
PEAK
L
PEAK
PEAK
B3, B4
11, 12
Inductor Switching Node.
Input Voltage Pin for the Device. Apply a voltage from 2.7V to 18V. Connect two 10µF ceramic
capacitors to PGND. Additional capacitance may be needed for input voltages close to 2.7V
C1
C2
C3
C4
2
IN
to prevent disabling the part by input voltage spikes which result in V < V
IN
.
UVLO
1
3
V
Internal Supply. Connect at least a 2.2µF capacitor to AGND.
L
Active-High Enable Input. Drive with a logic-high to enable the device and drive low to put the
device in True Shutdown mode. This pin should not be driven directly by IN, if IN is greater
than 5.5V.
EN
13, 14, EP
PGND
Power Ground.
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MAX17250
2.7V to 18V Input, Boost Converter with 0.1μA
True Shutdown, Short-Circuit Protection
and Selectable Input Current Limit
Functional Diagram
Boost Converter with Short-Circuit Protection and Programmable Input Current Limit
L1
CBST
0.1µF
2.2µH
LX
BST
PVH
MAX17250
HIGH-SIDE FET
CPVH
2 x 22µF
IN
CZ
UVLO
CIN
LOAD
SWITCH
2 x 10µF
EN
OUT
FB
TON/TOFF CONTROL
MODULATOR
COUT
10µF
RZ
LOW-
SIDE
FET
R1
R2
V
REF
PEAK CURRENT LIMIT
AND
ISET
CURRENT SENSE
REGULATOR
VL
C1
2.2µF
PGND
AGND
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MAX17250
2.7V to 18V Input, Boost Converter with 0.1μA
True Shutdown, Short-Circuit Protection
and Selectable Input Current Limit
MAX17250 provides over temperature and output short-
circuit protection. Should junction temperature be raised
Detailed Description
The MAX17250 compact, high-efficiency, step-up DC-DC
converters have low quiescent current and are guaranteed
to operate with input voltages ranging from 2.7V to 18V.
True Shutdown disconnects the input from the output,
eliminating the need for external load switches. Switching
frequencies up to 1MHz are supported. Tiny package
options, short-circuit protection, 18V operation, 800ns
fixed on time, and the three current-limit options allow the
user to minimize the total solution size.
to undesired levels, the device will stop switching and will
monitortemperatureasitstartstodecline.Oncetemperature
has fallen to manageable levels, switching will resume. The
output voltage short-circuit protection will cause the device
to stop switching once an output short-circuit condition is
detected upon which the output will be permanently latched
off. The device will have to be reset either by power cycling
or using enable signal to resume regulation.
Design Procedure
Feedback Resistor Divider Selection
for Output Voltage
The MAX17250 utilizes a fixed on-time, current-limited,
pulse-frequency-modulation (PFM) control scheme that
allows low quiescent current and high efficiency over a
wide output current range. The inductor current is limited
by the 1.85A/2.7A/3.5A low-side FET current limit or by
the 800ns switch maximum on-time. When the error
comparator senses that the feedback signal has fallen
below the regulation threshold, the low-side FET is turned
on. This is the beginning of a switching cycle and the
inductor current starts ramping up from the input source.
Once the on-time elapses or the maximum current limit
is reached the low-side FET turns off, the high-side FET
turns on and the inductor current starts discharging to
the output. The high-side FET turns off when the inductor
current reaches zero or if the feedback signal falls below
the regulation threshold after the minimum off time
(200ns) has elapsed. The MAX17250 PFM control scheme
allows for both continuous conduction mode (CCM) or
discontinuous conduction mode (DCM) operation.
The output voltage of the MAX17250 is set through the
resistor divider (R1, Rz, and R2) from VOUT to AGND,
as shown in the Typical Application Circuit. The bottom
resistor (R2) is recommended to be 10.0kΩ. This recom-
mendation is to minimize noise levels at the feedback
pin, which is relevant in continuous conduction mode of
operation. In applications where lower output power
is required and the device operates in discontinuous
conduction mode of operation, larger divider impedance
can be used to minimize current consumption. The top
resistor (R1 + Rz) is calculated by the equation below,
where 1.25V represents the internal reference voltage.
Recommended Rz value is 1kΩ. Because resistor
tolerance will have direct effect on V
resistors should have 1% accuracy or better.
accuracy, these
OUT
R1 + Rz = R2 x (V /1.25 - 1)
OUT
The switching frequency in CCM can be calculated by the
equation below.
Note: Recommended Cz values are: 10nF for output
voltages up to 10V, 4.7nF for output voltages
greater than 10V.
V
−
V
1
+
1
OUT
IN
fsw
=
=
t
t
t
ON
OFF
ON
V
Inductor and Peak Current Limit Selection
OUT
Inductor value depends on the output voltage setting. For
proper inductance selection, refer to Table 1.
For example, with an input voltage of 7.2V and an output
voltage of 12V, the switching frequency in CCM can be
calculated as:
f
= 1/800ns x (12 - 7.2)V/12V = 500kHz
SW
In DCM, the switching frequency varies with load current.
Table 1. Inductance Selection
If the input voltage (V ) is greater than the output
IN
OUTPUT VOLTAGE RANGE
14V to 18V
L (µH)
3.3
voltage (V
) by a diode drop (V
OUT
varies from
DIODE
~0.2V at light load to ~0.7V at heavy load), the output
voltage is clamped to a diode drop below the input voltage
8V to 14V
2.2
(i.e., V
= V - V
).
5V to 8V
1.5
OUT
IN
DIODE
3V to 5V
1.0
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MAX17250
2.7V to 18V Input, Boost Converter with 0.1μA
True Shutdown, Short-Circuit Protection
and Selectable Input Current Limit
The MAX17250 has a three-state ISET input pin used to
select the inductor peak current limit (I ), as shown in
If the calculated value of I
use the ISET = AGND setting for I
is between 1.3A and 2A,
INPEAK
(2.7A, typical).
PEAK
PEAK
the Table 2. ISET value is read when VL crosses its UVLO
threshold during power-up, or when EN transitions low-to-
high. (See VL UVLO in the Electrical Characteristics table).
If the calculated value of I
use the ISET = VL setting for I
is between 2A and 2.7A,
INPEAK
(3.5A, typical).
PEAK
For example, if the minimum input voltage is 6V, the
output voltage is 12V, and the output current is 500mA,
assuming the conversion efficiency is 92%,
The inductor peak current limit setting should be
determined as follows:
Calculate the inductor ripple current (∆I) using the
equation below.
∆I = (V x t )/L = (6V x 800ns)/(2.2µH) = 2.2A
IN
ON
I
= (V
x I )/(V x η)+ ∆I/2 =
OUT IN
INPEAK
OUT
V
×
t
(12V x 500mA)/(6V x 0.92) + 2.2A/2 = 2.2A
IN_MIN
ON
∆ I
=
L
So, the ISET = VL setting for I
be chosen.
(3.5A, typical) should
PEAK
where V
is the minimum input voltage, t
is the
ON
IN_MIN
800ns on time.
Capacitor Selection
Calculate the maximum input current (I
equation below.
) using the
Input capacitors reduce current peaks from the battery
and increase efficiency. For the input capacitor, choose a
ceramic capacitor because they have the lowest equivalent
series resistance (ESR), smallest size, and lowest cost.
Choose an acceptable dielectric, such as X5R or X7R.
Other capacitor types can be used as well but will have
larger ESRs. Due to ceramic capacitors’ capacitance
drop with DC bias, two standard 10µF ceramic capacitors
are recommended at the input for most applications. The
minimum recommended effective capacitance at the
input is 10µF for most applications. For lower input
voltage applications, the input capacitor value can be
reduced. However, additional capacitance may be needed
for input voltages close to 2.7V to prevent disabling the
INPEAK
V
× I
OUT
V
OUT
× η
∆ I
I
=
+
INPEAK
2
INMIN
where V
is the output voltage, I
is the maximum
OUT
OUT
load current, V
is the minimum input voltage and η
IN_MIN
is the conversion efficiency.
If the calculated value of I
the ISET = Open setting for I
is lower than 1.3A use
(1.85A, typical).
INPEAK
PEAK
Table 2. Inductor I
Selection Table
part by input voltage ripple which results in V < V
.
PEAK
IN
UVLO
For output and PVH capacitors refer to Table 3 for proper
selection.
ISET
VL
I
(A)
PEAK
3.5
The output ripple on the MAX17250 is small because the
ripple at PVH pin gets further filtered and attenuated by the
on-resistance of the load switch and the capacitance at OUT.
AGND
OPEN
2.7
1.85
Table 3. OUT and PVH Capacitor Selection
OUTPUT VOLTAGE RANGE
12V to 18V
C
(µF)
C
(µF)
OUT
PVH
3 x 22µF/25V/X7R
2 x 22µF/25V/X7R
2 x 22µF/16V/X5R
10µF/25V/X7R
10µF/25V/X7R
10µF/16V/X5R
8V to 12V
3V to 8V
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MAX17250
2.7V to 18V Input, Boost Converter with 0.1μA
True Shutdown, Short-Circuit Protection
and Selectable Input Current Limit
At low V
and high V
applications, where the
Duty Cycle Limitation
IN
OUT
MAX17250 is approaching maximum duty cycle limitation,
output current will be limited. Please refer to the Typical
Operating Characteristics for reference.
Maximum duty ratio MAX17250 can provide is 78%.
Whether specific application meets this reqirement can be
checked using the following formula
Enabling MAX17250
D = (1 - ((V
x η))/V
) < 78%
OUT
IN MIN
The MAX17250 has a dedicated EN pin. This pin can
be driven by a digital signal. It is recommended that the
Where,
D is duty cycle.
digital signal to enable the device after V crosses the
IN
V
V
is minimum input voltage.
IN MIN
UVLO threshold.
is output voltage.
OUT
In applications where the EN pin is not driven, it can be
η is efficiency.
pulled high to V . If V range is below 5.5V, EN can be
IN
IN
Output Current Limitation
connected directly to V . If V is above, resistor divider
IN
IN
needs to be used. The divider should be designed that
EN pin voltage is well above its threshold at the instant
device starts regulation. This will assure that sag appearing
The output current will be limited by the input peak
current limit selection for a specific application. The output
current expressed as a function of the Peak Input Current
is shown below:
at V due to enabled regulation will not cause EN being
IN
toggled. Fast transient at enable that makes device
disable and re-enable can cause device not to power up
properly, including misreading the peak input current limit
setting. In some cases, a small value capacitor from the
EN pin to GND can be used. For high input voltage applications,
voltage at the EN pin must not exceed its rating.
I
= ((I
- ∆I/2) x (V x η))/V
OUT MAX
PEAK IN OUT
For example, for 7.2V , 12V
application with
OUT
IN
efficiency of 92% maximum output current recommended
is 0.76A which will allow 30% margin to the peak input
current limit set to 3.5A.
I
= I /1.3 = 3.5A/1.3 = 2.7A
LIMIT
PCB Layout Guidelines
PEAK MAX
Minimize trace lengths to reduce parasitic capacitance,
inductance and resistance, and radiated noise. Keep the
main power path from IN, LX, PVH, OUT, and PGND as
tight and short as possible. Minimize the surface area
used for LX since this is the noisiest node. The trace
between the feedback resistor divider and the FB pin
should be as short as possible and should be isolated
from the noisy power path. VL decoupling capacitor must
be as close to the pin as possible referenced to PGND
pin. Refer to the EV kit layout for best practices.
∆I = (V
t
)/L = (7.2V x 800ns)/(2.2µH) = 2.62A
IN ON
I
= ((I
- ∆I/2) x (V x η)) / V
= 0.76A
OUT
OUT MAX
PEAK
IN
In addition, the output current is a function of the device
package and PCB thermal performance. The maximum
junction temperature should be restricted to 125°C under
normal operating conditions. Calculate the maximum
allowable power dissipation and keep the actual power
dissipation less than or equal to that. The maximum
power dissipation limit is determined using the following
equation.
The PCB layout is important for robust thermal design.
The junction to ambient thermal resistance of the
package greatly depends on the PCB type, layout, and
pad connections. Using thick PCB copper and having the
SW, PVH, VOUT, and PGND copper pours will enhance
the thermal performance. The TDFN package would
have smaller junction to ambient thermal resistance and,
therefore, better thermal performance. It has a large
thermal pad under the package which creates excellent
thermal path to PCB. This pad is electrically connected to
PGND. Its PCB pad should have multiple thermal vias con-
nectingthepadtointernalPGNDplane.Thermalviasshould
either be capped or have small diameter to minimize
solder wicking and voids.
Power Disipation Max (W) = ((125°C - T °C))/
A
(R
(°C)/W)
θJA
where,
T is the maximum ambient temperature for the application.
A
RθJA is the junction-to-ambient thermal resistance given
in the Package Information section.
So, for the same example as above, 7.2V , 12V
,
OUT
IN
I
= 0.76A internal power dissipation will be 0.3W. This
OUT
will cause the junction temperature to rise 22°C above
ambient temperature using the WLP package.
The TDFN package would have smaller junction to
ambient thermal resistance and therefore better thermal
performance.
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MAX17250
2.7V to 18V Input, Boost Converter with 0.1μA
True Shutdown, Short-Circuit Protection
and Selectable Input Current Limit
Ordering Information
PART NUMBER
MAX17250ANC+
MAX17250ATD+
T
TEMPERATURE RANGE
-40°C to +125°C
PIN-PACKAGE
12 WLP
ON
800ns
800ns
-40°C to +125°C
14 TDFN
+ Denotes a lead(Pb)-free/RoHS-compliant package.
T Denotes tape-and-reel.
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MAX17250
2.7V to 18V Input, Boost Converter with 0.1μA
True Shutdown, Short-Circuit Protection
and Selectable Input Current Limit
Revision History
REVISION REVISION
PAGES
DESCRIPTION
CHANGED
NUMBER
DATE
0
6/18
Initial release
—
Updated Typical Application Circuit, Electrical Characteristics, Typical Operating
Characsteristics, and Ordering Information
1
2
9/18
8/19
1, 3, 5, 12
1, 9–12
Updated Typical Application Circuit, Detailed Description, Table 3, and Ordering
Information
For pricing, delivery, and ordering information, please visit Maxim Integrated’s online storefront at https://www.maximintegrated.com/en/storefront/storefront.html.
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses
are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits)
shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
©
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
2019 Maxim Integrated Products, Inc.
│ 13
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