MAXM17900AMB [MAXIM]
4V to 24V, 100mA, Compact Step-Down Power Module;
| 型号： | MAXM17900AMB |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | 4V to 24V, 100mA, Compact Step-Down Power Module |
| 文件： | 总17页 (文件大小：1224K) |
| 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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MAXM17900
4V to 24V, 100mA,
Compact Step-Down Power Module
General Description
Benefits and Features
● Easy to Use
The Himalaya series of voltage regulator ICs and power
modules enable cooler, smaller, and simpler power-
supply solutions. The MAXM17900 is a high-efficiency,
synchronous, step-down DC-DC power module with inte-
grated controller, MOSFETs, compensation components,
and inductor that operates over a wide input voltage
range. The module operates from 4V to 24V input voltage
and delivers up to 100mA output current over a program-
mable output voltage from 0.9V to 5.5V. The module sig-
nificantly reduces design complexity, manufacturing risks
and offers a true plug-and-play power supply solution,
reducing the time-to-market.
• Wide 4V to 24V Input
• Adjustable 0.9V to 5.5V Output
• ±1.75% Feedback-Voltage Accuracy
• Up to 100mA Output Current Capability
• Internally Compensated
• All Ceramic Capacitors
● High Efficiency
• Fixed-Frequency PWM
• Pulse Frequency Modulation (PFM) Mode to
Enhance Light-Load Efficiency
• Shutdown Current as Low as 1.2μA (typ)
The MAXM17900 employs peak-current-mode control
architecture. To reduce input inrush current, the device
offers a soft-start feature including a default soft-start time
of 5.1ms.
● Flexible Design
• Programmable Soft-Start and Prebias Startup
• Open-Drain Power Good Output (RESET Pin)
• Programmable EN/UVLO Threshold
The MAXM17900 is available in a low profile, compact
10-pin 2.6mm x 3mm x 1.5mm uSLIC™ package.
● Rugged
• Complies with CISPR22 (EN55022) Class B
Conducted and Radiated Emissions
• Passes Drop, Shock, and Vibration Standards–
JESD22-B103, B104, B111
Applications
● Industrial Sensors and Encoders
● 4mA–20mA Current-Loop Powered Sensors
● LDO Replacement
● HVAC and Building Control
● Battery-Powered Equipment
● Robust Operation
• Hiccup Overcurrent Protection
• Overtemperature Protection
• -40°C to +125°C Ambient Operating Temperature /
-40°C to +150°C Junction Temperature
uSLIC is a trademark of Maxim Integrated Products, Inc.
Ordering Information appears at end of data sheet.
Typical Application Circuit
MAXM17900
V
12V
V
OUT
5V, 100mA
IN
IN
OUT
C
10µF
OUT
C
2.2µF
IN
EN/UVLO
R1
261kΩ
GND
RESET
RT/SYNC
LX
MODE
FB
SS
R3
69.8kΩ
R2
49.9kΩ
C
= 2.2µF: C2012X7R1H225K125AC
IN
C
= 10µF: GRM21BR70J106K
OUT
19-100210; Rev 3; 11/20
MAXM17900
4V to 24V, 100mA,
Compact Step-Down Power Module
Absolute Maximum Ratings
IN, EN/UVLO to GND............................................-0.3V to +29V
LX to GND.......................................................-0.3V to IN +0.3V
OUT to GND............................................................-0.3V to +7V
RT/SYNC, SS, FB, MODE to GND.........................-0.3V to +6V
RESET...................................................................-0.3V to +18V
Output Short-Circuit Duration....................................Continuous
Junction Temperature (Note 1)........................................+150°C
Storage Temperature Range............................ -55°C to +125°C
Lead Temperature (soldering, 10s) .................................+260°C
Soldering Temperature (reflow).......................................+260°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.
Note 1: Junction temperature greater than +125°C degrades operating lifetimes
Package Information
PACKAGE TYPE: 10-PIN uSLIC
Package Code
M102A3+1
21-100094
90-100027
Outline Number
Land Pattern Number
THERMAL RESISTANCE FOUR-LAYER BOARD
Junction to Ambient (θ
)
30.6°C/W
JA
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 resistance measured on Evaluation Board, Natural convection. For detailed information on package thermal consid-
erations, refer to www.maximintegrated.com/thermal-tutorial.
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MAXM17900
4V to 24V, 100mA,
Compact Step-Down Power Module
Electrical Characteristics
(V = 12V, V
= 0V, V = 0.85V, V
= 1.5V, RT/SYNC = 69.8kΩ, LX = SS = RESET = unconnected, MODE = GND; T = -40°C
IN
GND
FB
EN/UVLO
A
to +125°C, unless otherwise noted. Typical values are at T = +25°C. All voltages are referenced to GND, unless otherwise noted) (Note 2)
A
PARAMETER
INPUT SUPPLY (IN)
Input Voltage Range
Input Shutdown Current
SYMBOL
CONDITIONS
MIN
TYP
MAX UNITS
V
4
24
V
IN
I
V
= 0V, T = +25°C
0.67
1.2
2.25
µA
IN-SH
EN/UVLO
A
V
V
= Normal switching, V
= 0V,
MODE
FB
I
800
30
1100
1950
110
Q-PWM
= 3.3V
OUT
Input Supply Current
µA
I
V
MODE
= unconnected
62
Q-PFM
MODULE OUTPUT PIN (OUT)
Output Line Regulation
Accuracy
V
= 4V to 24V, V
= 0
= 3.3V,
IN
OUT
0.1
0.3
mV/V
I
LOAD
Output Load Regulation
Accuracy
Tested with I
= 0A and 100mA
OUT
= 3.3V
mV/mA
V
OUT
ENABLE/UVLO (EN/UVLO)
V
V
V
V
rising
falling
1.2
1.1
1.25
1.15
0.72
1.3
1.2
ENR
EN/UVLO
EN/UVLO
EN/UVLO
V
EN/UVLO Threshold
V
ENF
V
falling, true shutdown
= 1.3V, T = +25°C
EN-TRUESD
I
EN/UVLO Leakage Current
V
-100
-1
+100
+1
nA
EN
EN/UVLO
A
LX
V = (V
+ 1V)
GND
V
= 0V, T = +25°C,
EN
A
LX
I
LX Leakage Current
µA
LX-LKG
to (V - 1V) V
= float
IN
OUT
SOFT-START (SS)
Soft-Start Time
t
No SS cap
4.4
4.7
5.1
5
5.8
5.3
ms
µA
SS
I
V
= 0.4V
SS Charging Current
FEEDBACK (FB)
SS
SS
MODE = OPEN
MODE = GND
0.786 0.812 0.830
V
FB Regulation Voltage
V
FB-REG
0.786
-100
0.8
0.814
+120
I
FB Input Leakage Current
V
= 0.81V, T = 25°C
nA
FB
FB
A
CURRENT LIMIT
I
V
Current-Limit
100
178
-1
mA
mA
OUT
SOURCE-LIMIT
MODE = OPEN
MODE = GND
I
V
Current-Limit
OUT
SINK-LIMIT
-74
-50
OSCILLATOR (RT/SYNC)
R
R
R
R
R
= 422kΩ
= 191kΩ
= 130kΩ
= 69.8kΩ
= 45.3kΩ
85
100
220
322
600
900
120
250
350
640
973
RT
RT
RT
RT
RT
200
295
540
813
Switching Frequency
f
kHz
SW
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MAXM17900
4V to 24V, 100mA,
Compact Step-Down Power Module
Electrical Characteristics (continued)
(V = 12V, V
= 0V, V = 0.85V, V
= 1.5V, RT/SYNC = 69.8kΩ, LX = SS = RESET = unconnected, MODE = GND; T = -40°C
IN
GND
FB
EN/UVLO A
to +125°C, unless otherwise noted. Typical values are at T = +25°C. All voltages are referenced to GND, unless otherwise noted) (Note 2)
A
PARAMETER
SYMBOL
CONDITIONS
MIN
100
TYP
MAX UNITS
Switching Frequency
Adjustable Range
See the Switching Frequency (RT/SYNC)
section for details
900
900
kHz
kHz
ns
1.1 x
SYNC Input Frequency
f
SW
SYNC Pulse Minimum
Off-Time
40
V
SYNC Rising Threshold
Hysteresis
1
1.22
0.18
1.48
SYNC-H
V
V
0.115
0.265
SYNC-HYS
Number of SYNC Pulses to
Enable Synchronization
1
Cycles
MODE
V
V
PFM Threshold
Hysterisis
1
1.22
0.19
1.48
V
V
MODE-PFM
MODE-HYS
TIMING
t
Minimum On-Time
46
90
90
94
152
98
ns
%
ON-MIN
V
= 0.98 x V
≤ 600kHz
FB
FB-REG
f
SW
D
Maximum Duty Cycle
MAX
600kHz < f
< 900kHz,
FB-REG
SW
= 0.98 x V
87
92
51
V
FB
Hiccup Timeout
ms
RESET
FB Threshold for RESET
Rising
V
V
V
rising
falling
93
90
95
92
97
94
%
%
FB-OKR
FB
FB Threshold for RESET
Falling
V
FB-OKF
FB
RESET Delay after FB
Reaches 95% Regulation
2.08
0.23
ms
V
RESET Output Level Low
I
= 1mA
RESET
RESET Output Leakage
Current
V
= 1.01 x V
, T = +25°C
1
µA
FB
FB-REG
A
THERMAL SHUTDOWN
Thermal-Shutdown Threshold
Thermal-Shutdown Hysteresis
Temperature rising
160
20
°C
°C
Note 2: All limits are 100% tested at +25°C. Limits over temperature are guaranteed by design.
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MAXM17900
4V to 24V, 100mA,
Compact Step-Down Power Module
Typical Operating Characteristics
(V = 12V, V
= 1.5V, RT/SYNC = 69.8kΩ, T = +25°C unless otherwise noted)
A
IN
EN/UVLO
EFFICIENCY vs. LOAD CURRENT
(5V OUTPUT, PWM MODE, fSW = 600kHz)
EFFICIENCY vs. LOAD CURRENT
(3.3V OUTPUT, PWM MODE, fSW = 600kHz)
LOAD AND LINE REGULATION
(3.3V OUTPUT, PWM MODE)
toc02
toc03
toc01
3.350
3.345
3.340
3.335
3.330
3.325
3.320
3.315
3.310
3.305
3.300
100
90
80
70
60
50
40
30
20
10
100
90
80
70
60
50
40
30
20
10
VIN = 24V
VIN = 6V
VIN = 24V
VIN = 10V
VIN = 24V
VIN = 12V
VIN = 12V
VIN = 12V
VIN = 6V
0
10 20 30 40 50 60 70 80 90 100
LOAD CURRENT (mA)
0
20
40
60
80
100
0
20
40
60
80
100
LOAD CURRENT (mA)
LOAD CURRENT (mA)
LOAD AND LINE REGULATION
(5V OUTPUT, PWM MODE)
EFFICIENCY vs. LOAD CURRENT
EFFICIENCY vs. LOAD CURRENT
(3.3V OUTPUT, PFM MODE)
(5V OUTPUT, PFM MODE)
toc04
toc06
toc05
5.05
5.00
4.95
4.90
4.85
4.80
4.75
4.70
90
80
70
60
50
40
30
20
10
100
90
80
70
60
50
40
30
20
10
VIN = 24V
VIN = 10V
VIN = 12V
VIN = 12V
VIN = 24V
VIN = 12V
VIN = 24V
MODE = OPEN
MODE = OPEN
1
10
100
0
10 20 30 40 50 60 70 80 90 100
LOAD CURRENT (mA)
1
10
LOAD CURRENT (mA)
100
LOAD CURRENT (mA)
OUTPUT VOLTAGEvs. LOAD CURRENT
OUTPUT VOLTAGEvs. LOAD CURRENT
SOFT-START FROM EN/UVLO
(3.3V OUTPUT, 100mA LOAD CURRENT, PWM MODE)
(3.3V OUTPUT, PFM MODE)
(5V OUTPUT, PFM MODE)
toc07
toc08
toc09
3.6
3.5
3.4
3.3
3.2
3.1
5.2
5.1
5.0
4.9
4.8
4.7
5V/div
VEN/UVLO
1V/div
VOUT
IOUT
VIN = 12V
50mA/div
5V/div
VIN = 12V
VIN = 24V
VIN = 24V
VRESET
0
20
40
60
80
100
0
20
40
60
80
100
1ms/div
LOAD CURRENT (mA)
LOAD CURRENT (mA)
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MAXM17900
4V to 24V, 100mA,
Compact Step-Down Power Module
Typical Operating Characteristics (continued)
(V = 12V, V
= 1.5V, RT/SYNC = 69.8kΩ, T = +25°C unless otherwise noted)
IN
EN/UVLO
A
SOFT-START WITH 3V PREBIAS
(5V OUTPUT, NO LOAD )
SOFT-START FROM EN/UVLO
(5V OUTPUT, 100mA LOAD CURRENT, PWM MODE)
SHUTDOWN FROM EN/UVLO
(5V OUTPUT, 100mA LOAD CURRENT, PWM MODE)
toc10
toc12
toc11
VEN/UVLO
5V/div
1V/div
5V/div
5V/div
2V/div
VEN/UVLO
VEN/UVLO
VOUT
IOUT
2V/div
VOUT
IOUT
50mA/div
5V/div
50mA/div
5V/div
VOUT
VRESET
VRESET
5V/div
VRESET
1ms/div
1ms/div
1ms/div
SOFT-START WITH 3V PREBIAS
(100mA LOAD CURRENT, 5V OUTPUT, PWM MODE)
STEADY-STATE SWITCHING WAVEFORMS
(5V OUTPUT, 0.1A LOAD CURRENT)
STEADY-STATE SWITCHING WAVEFORMS
(5V OUTPUT, NO LOAD CURRENT)
toc14
toc15
toc13
VEN/UVLO
10mV/div
VOUT
(AC)
5V/div
VOUT
(AC)
10mV/div
2V/div
VOUT
IOUT
100mA/div
VRESET
2V/div
5V/div
VLX
5V/div
VLX
1ms/div
2μs/div
2μs/div
SWITCHING FREQUENCY
vs. INPUT VOLTAGE
STEADY-STATE SWITCHING WAVEFORMS
AVERAGE CURRENT LIMIT
(5V OUTPUT, 0.02A LOAD CURRENT, PFM MODE)
toc16
toc17
toc18
240
230
220
210
200
190
180
170
160
630
620
610
600
590
580
570
560
VOUT
(AC)
TEMP = 85°C
50mV/div
-40°C
25°C
85°C
TEMP = 25°C
5V/div
VLX
TEMP = -40°C
0
5
10
15
20
25
10μs/div
0
5
10
15
20
25
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
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MAXM17900
4V to 24V, 100mA,
Compact Step-Down Power Module
Typical Operating Characteristics (continued)
(V = 12V, V
= 1.5V, RT/SYNC = 69.8kΩ, T = +25°C unless otherwise noted)
IN
EN/UVLO
A
LOAD CURRENT TRANSIENT RESPONSE
SHUTDOWN CURRENT
vs. INPUT VOLTAGE
(VIN = 12V, VOUT = 5V, IOUT = 0.05A TO 0.1A)
toc19
toc20
3.00
2.50
2.00
1.50
1.00
0.50
0.00
50mV/div
(AC
VOUT
COUPLED)
25°C
TEMP = 25°C
IOUT
50mA/div
0
5
10
15
20
25
100µs/div
INPUT VOLTAGE (V)
LOAD CURRENT TRANSIENT RESPONSE
(PFM MODE
LOAD CURRENT TRANSIENT RESPONSE
(PFM MODE
VIN = 12V, VOUT = 5V, IOUT = 25mATO 75mA)
VIN = 12V, VOUT = 3.3V, IOUT = 20mATO 75mA)
toc22
toc21
100mV/div
(AC
COUPLED)
100mV/div
(AC
COUPLED)
VOUT
VOUT
AC
(AC)
(
)
50mA/div
IOUT
50mA/div
IOUT
200µs/div
200µs/div
LOAD CURRENT TRANSIENT RESPONSE
(VIN = 12V, VOUT = 5V, IOUT = 0A TO 0.05A)
LOAD CURRENT TRANSIENT RESPONSE
(VIN = 12V, VOUT = 3.3V, IOUT = 0.05ATO 0.1A)
toc24
toc23
50mV/div
(AC
COUPLED)
VOUT
50mV/div
(AC
COUPLED)
VOUT
50mA/div
IOUT
IOUT
50mA/div
200µs/div
100µs/div
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MAXM17900
4V to 24V, 100mA,
Compact Step-Down Power Module
Typical Operating Characteristics (continued)
(V = 12V, V
= 1.5V, RT/SYNC = 69.8kΩ, T = +25°C unless otherwise noted)
IN
EN/UVLO
A
EXTERNAL SYNCHRONIZATION WITH 900kHz
CLOCK FREQUENCY
LOAD CURRENT TRANSIENT RESPONSE
(VIN = 12V, VOUT = 3.3V, IOUT = 0A TO 0.05A)
(VIN = 12V, VOUT = 5V, IOUT = 0.1A)
toc25
toc26
5V/div
50mV/div
(AC
COUPLED)
VOUT
VLX
2V/div
VSYNC
IOUT
50mA/div
200µs/div
2µs/div
OUTPUT CURRENT
DURING STEADY-STATE SHORT
OVERLOAD PROTECTION
toc28
toc27
VOUT
2V/div
5V/div
100mA/div
IOUT
LX
40µs/div
20ms/div
BODE PLOT
(VIN = 12V, VOUT = 3.3V, IOUT = 0.1A)
BODE PLOT
(VIN = 12V, VOUT = 5V, IOUT = 0.1A)
toc30
toc29
40
30
90
80
70
60
50
40
30
20
10
0
40
30
100
PHASE
90
80
70
60
50
40
30
20
10
0
PHASE
20
20
10
10
0
0
GAIN
GAIN
-10
-20
-30
-40
-10
-20
-30
-40
fCR = 23.2kHz,
fCR = 28.1kHz,
PHASE MARGIN = 67.8°
PHASE MARGIN = 66.2°
105
104
103
105
103
104
FREQUENCY (Hz)
FREQUENCY (Hz)
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MAXM17900
4V to 24V, 100mA,
Compact Step-Down Power Module
Pin Configuration
TOP VIEW
1
2
10 IN
LX
GND
+
9
EN/UVLO
MAXM17900
MODE
RESET
3
4
8
7
RT/SYNC
SS
OUT
5
6
FB
(“+” INDICATES PIN 1 OF THE MODULE)
Pin Description
PIN NAME
PIN #
FUNCTION
Switching Node. LX is high impedance when the device is in shutdown. Do not connect any external
components to this pin.
LX
1
Ground. Connect GND to the power ground plane. Connect all the circuit ground connections together
at a single point. See the PCB Layout Guidelines section.
GND
2
3
PFM/PWM Mode Selection Input. Connect MODE to GND to enable the fixed-frequency PWM. Leave
MODE unconnected for light-load PFM operation.
MODE
Open-Drain Reset Output. Pull up RESET to an external power supply less than or equal to 16V with
an external resistor. RESET pulls low if FB drops below 92% of its set value. RESET goes high 2ms
after FB rises above 95% of its set value.
RESET
4
Module output pin. Connect a capacitor from OUT to GND. See PCB Layout Guidelines section for
more connection details.
OUT
FB
5
6
7
Output Feedback Connection. Connect FB to a resistor-divider between OUT and GND to set the
output voltage.
Soft-Start Capacitor Input. Connect a capacitor from SS to GND to set the soft-start time. Leave SS
unconnected for default 5.1ms internal soft-start.
SS
Oscillator Timing Resistor Input. Connect a resistor from RT/SYNC to GND to program the switching
frequency from 100kHz to 900kHz. See the Switching Frequency (RT/SYNC) section for details. An
external pulse can be applied to RT/SYNC through a coupling capacitor to synchronize the internal
clock to the external pulse frequency.
RT/SYNC
8
Active-High, Enable/Undervoltage-Detection Input. Pull EN/UVLO to GND to disable the module
output. Connect EN/UVLO to IN for always-on operation. Connect a resistor-divider between IN, EN/
UVLO, and GND to program the input voltage at which the module is enabled and turns on.
EN/UVLO
IN
9
Power Module Input. Connect a ceramic capacitor from IN to GND for bypassing. Place the capacitor
close to the IN and PGND pins. See Table 1 for more details.
10
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MAXM17900
4V to 24V, 100mA,
Compact Step-Down Power Module
Functional Diagram
MAXM17900
IN
LDO
HIGH-SIDE DRIVER
MODE
LX
1.22V
PEAK
CURRENT-MODE
CONTROLLER
RT/SYNC
EN/UVLO
OSCILLATOR
100µH
OUT
LOW-SIDE DRIVER
1.25V
GND
SS
RESET
FB
PGOOD LOGIC
0.76V
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MAXM17900
4V to 24V, 100mA,
Compact Step-Down Power Module
tion mode, turns on all internal blocks, and again com-
mences the process of delivering pulses of energy to the
output until it reaches 102% (typ) of the nominal output
voltage. The device naturally exits PFM mode when the
inductor peak current increases to a magnitude approxi-
Detailed Description
The MAXM17900 synchronous step-down power module
with integrated MOSFETs and inductor, operates over a
4V to 24V input voltage range. The module can deliver
output current up to 100mA at output voltages of 0.9V to
5.5V. The feedback voltage is accurate to within ±1.75%
over -40°C to +125°C.
mately equal to I
.
PFM
Enable Input (EN/UVLO) and Soft-Start (SS)
The device uses an internally-compensated, peak cur-
rent mode control architecture. On the rising edge of
the internal clock, the high-side pMOSFET turns on. An
internal error amplifier compares the feedback voltage to
a fixed internal reference voltage and generates an error
voltage. The error voltage is compared to a sum of the
current-sense voltage and a slope-compensation voltage
by a PWM comparator to set the “on-time.” During the
on-time of the pMOSFET, the inductor current ramps up.
For the remainder of the switching period (off-time), the
pMOSFET is kept off and the low-side nMOSFET turns
on. During the off-time, the inductor releases the stored
energy as the inductor current ramps down, providing cur-
rent to the output. Under overload conditions, the cycle-
by-cycle current- limit feature limits inductor peak current
by turning off the high-side pMOSFET and turning on the
low-side nMOSFET.
When EN/UVLO voltage increases above 1.25V (typ), the
device initiates a soft-start sequence and the duration of
the soft-start depends on the status of the SS pin voltage
at the time of power-up. If the SS pin is not connected, the
device uses a fixed 5.1ms (typ) internal soft-start to ramp
up the internal error-amplifier reference. If a capacitor is
connected from SS to GND, a 5μA current source charges
the capacitor and ramps up the SS pin voltage. The SS
pin voltage is used as a reference for the internal error
amplifier. Such a reference ramp up allows the output
voltage to increase monotonically from zero to the final
set value independent of the load current.
EN/UVLO can be used as an input voltage UVLO adjust-
ment input. An external voltage-divider between IN and
EN/UVLO to GND adjusts the input voltage at which
the device turns on or off. See the Setting the Input
Undervoltage-Lockout Level section for details. If input
UVLO programming is not desired, connect EN/UVLO to
IN (see the Electrical Characteristics table for EN/UVLO
rising and falling-threshold voltages). Driving EN/UVLO
low disables both power MOSFETs, as well as other inter-
nal circuitry, and reduces IN quiescent current to below
1.2μA. The SS capacitor is discharged with an internal
pulldown resistor when EN/UVLO is low. If the EN/UVLO
pin is driven from an external signal source, a series
resistance of minimum 1kΩ is recommended to be placed
between the signal source output and the EN/UVLO pin,
to reduce voltage ringing on the line.
Mode Selection (MODE)
The device features a MODE pin for selecting either
forced-PWM or PFM mode of operation. If the MODE pin
is left unconnected, the device operates in PFM mode
at light loads. If the MODE pin is grounded, the device
operates in a constant-frequency forced-PWM mode at all
loads. The mode of operation cannot be changed on-the
fly during normal operation of the device.
In PWM mode, the inductor current is allowed to go
negative. PWM operation is useful in frequency-sensitive
applications and provides fixed switching frequency at
all loads. However, the PWM mode of operation gives
lower efficiency at light loads compared to PFM mode of
operation.
Switching Frequency (RT/SYNC)
Switching frequency of the device can be programmed
from 100kHz to 900kHz by using a resistor connected
from RT/SYNC to GND. The switching frequency (f
is related to the resistor connected at the RT/SYNC pin
)
SW
PFM mode disables negative inductor current and addi-
tionally skips pulses at light loads for high efficiency. In
PFM mode, the inductor current is forced to a fixed peak
(R ) by the following equation, where R is in kΩ and f
T
T
SW
is in kHz:
of 72mA (typ) (I ) every clock cycle until the output
PFM
rises to 102% (typ) of the nominal voltage. Once the
output reaches 102% (typ) of the nominal voltage, both
high-side and low-side FETs are turned off and the device
enters hibernation mode until the load discharges the
output to 101% (typ) of the nominal voltage. Most of the
internal blocks are turned off in hibernation mode to save
quiescent current. Once the output falls below 101% (typ)
of the nominal voltage, the device comes out of hiberna-
42000
R
=
T
f
SW
The switching frequency in ranges of 130kHz to 160kHz
and 230kHz to 280kHz are not allowed for user pro-
gramming to ensure proper configuration of the internal
adaptive-loop compensation scheme.
Maxim Integrated
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MAXM17900
4V to 24V, 100mA,
Compact Step-Down Power Module
voltage is then smoothly ramped up to the target value
in alignment with the internal reference. Such a feature is
useful in applications where digital integrated circuits with
multiple rails are powered.
External Synchronization
The RT/SYNC pin can be used to synchronize the
device’s internal oscillator to an external system clock.
The external clock should be coupled to the RT/SYNC
pin through a 47pF capacitor, as shown in Figure 1. The
external clock logic high level should be higher than 3V,
logic low level lower than 0.5V and the duty cycle of the
external clock should be in the range of 10% to 70%.
The RT resistor should be selected to set the switching
frequency 10% lower than the external clock frequency.
The external clock should be applied at least 500μs after
enabling the device for proper configuration of the internal
loop compensation.
Operating Input-Voltage Range
The maximum operating input voltage is determined by
the minimum controllable on-time, while the minimum
operating input voltage is determined by the maximum
duty cycle and circuit voltage drops. The minimum and
maximum operating input voltages for a given output volt-
age should be calculated as follows:
V
+ (I
× 8.6)
OUT
OUT
V
=
+ (I
× 2.5)
IN(MIN)
OUT
D
Reset Output (RESET)
MAX
The device includes an open-drain RESET output to
monitor output voltage. RESET should be pulled up with
an external resistor to the desired external power supply
less than or equal to 16V. RESET goes high impedance
2ms after the output rises above 95% of its nominal set
value and pulls low when the output voltage falls below
92% of the set nominal output voltage. RESET asserts
low during the hiccup timeout period.
f
SW
for duty cycle, D > 0.3 : V
> 4.8× V
−
OUT
IN(MIN)
42000
V
OUT
× f
V
=
IN(MAX)
t
ON(MIN) SW
where,
V
= Steady-state output voltage
OUT
I
f
= Maximum load current
OUT
Startup Into a Pre-biased Output
= Switching frequency (max)
SW
The device supports monotonic startup into a pre-biased
output. When the module starts into a pre-biased output,
both the high-side and low-side switches are turned off
so that the module does not sink current from the output.
High-side and low-side switches do not start switching
until the PWM comparator commands the first PWM
pulse, at which point switching commences. The output
D
= Maximum duty cycle
MAX
t
= Worst case minimum controllable switch on-
ON(MIN)
time (152ns).
Overcurrent Protection (OCP), Hiccup Mode
The device implements a HICCUP-type overload protec-
tion scheme to protect the inductor and internal FETs under
output short-circuit conditions. When the overcurrent event
occurs, the part enters hiccup mode. In this mode, the part
is initially operated with hysteretic cycle-by-cycle peak-
current limit that continues for a time period equal to twice
the soft-start time. The part is then turned off for a fixed
51ms hiccup timeout period. This sequence of hysteretic
inductor current waveforms, followed by a hiccup timeout
period, continues until the short/overload on the output is
removed. Since the inductor current is bound between two
limits, inductor current runway never happens.
MAXM17900
47pF
RT/SYNC
CLOCK
SOURCE
R
T
Thermal Shutdown
V
LOGIC-HIGH
DUTY
Thermal shutdown limits the total power dissipation in the
module. When the junction temperature exceeds +160°C,
an on-chip thermal sensor shuts down the device, turns
off the internal power MOSFETs, allowing the device
to cool down. The device turns on after the junction
temperature cools by approximately 20°C.
V
LOGIC-LOW
Figure 1. Synchronization to an External Clock
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MAXM17900
4V to 24V, 100mA,
Compact Step-Down Power Module
Setting the Input Undervoltage-Lockout Level
Application Information
The device offers an adjustable input undervoltage-lock-
out level. Set the voltage at which the device turns on with
a resistive voltage-divider connected from IN to GND (see
Figure 2). Connect the center node of the divider to EN/
UVLO. Choose R1 to be 3.3MΩ max and then calculate
R2 as follows:
Input Capacitor Selection
Small ceramic input capacitors are recommended. The
input capacitor reduces peak current drawn from the
power source and reduces noise and voltage ripple on
the input caused by the switching circuitry. It is recom-
mended to select the input capacitor of the module to
keep the input-voltage ripple under 2% of the minimum
input voltage, and to meet the maximum ripple-current
requirements.
1.25×R
1
R2 =
V
−1.25
INU
where V
to turn on.
is the voltage at which the device is required
INU
Output Capacitor Selection
Small ceramic X7R-grade output capacitors are recom-
mended for the device. The output capacitor has two
functions. It stores sufficient energy to support the output
voltage under load transient conditions and stabilizes the
device’s internal control loop. Usually the output capacitor
is sized to support a step load of 50% of the maximum
output current in the application, such that the output
voltage deviation is less than 3%. Calculate the minimum
required output capacitance from the following equations:
Adjusting the Output Voltage
The output voltage can be programmed from 0.9V to 5.5V.
Different output voltage needs to use different switching
frequency (see Table 1). Set the output voltage by con-
necting a resistor-divider from output to FB to GND (see
Figure 3). Choose R5 in the range of 25kΩ to 100kΩ and
calculate R4 with the following equation:
V
FREQUENCY RANGE
MINIMUM OUTPUT
CAPACITANCE (µF)
OUT
R4 = R5×
−1
(kHZ)
0.8
50
100 to 130
160 to 230
280 to 900
V
V
V
OUT
25
V
IN
IN
MAXM17900
OUT
17
R1
R2
EN/UVLO
OUT
It should be noted that dielectric materials used in ceramic
capacitors exhibit capacitance loss due to DC bias lev-
els and should be appropriately de-rated to ensure the
required output capacitance is obtained in the application.
GND
Soft-Start Capacitor Selection
Figure 2. Adjustable EN/UVLO Network
The device offers a 5.1ms internal soft-start when the SS
pin is left unconnected. When adjustable soft-start time is
required, connect a capacitor from SS to GND to program
the soft-start time. The minimum soft-start time is related
V
OUT
MAXM17900
to the output capacitance (C
) and the output voltage
R4
R5
OUT
(V
) by the following equation:
OUT
FB
t
> 0.05 x C
x V
OUT OUT
SS
where t is in milliseconds and C
is in µF.
OUT
SS
GND
Soft-start time (t ) is related to the capacitor connected
SS
at SS (C ) by the following equation:
SS
C
= 6.25 x t
SS
SS
Figure 3. Circuit for Setting the Output Voltage.
where t is in milliseconds and C is in nF.
SS
SS
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MAXM17900
4V to 24V, 100mA,
Compact Step-Down Power Module
Table 1. Component Selection Table
V
(V)
V
(V)
C
f
(kHz)
R3 (kΩ)
191
191
140
140
105
70
R4 (kΩ)
6.19
24.9
43.2
61.9
107
R5 (kΩ)
49.9
C
OUT
OUT
IN
IN
SW
0.9
4 to 24
4 to 24
4 to 24
4 to 24
4.5 to 24
6 to 24
10 to 24
10 to 24
1 × 2.2μF 1206 50V X7R
1 × 2.2μF 1206 50V X7R
1 × 2.2μF 1206 50V X7R
1 × 2.2μF 1206 50V X7R
1 × 1μF 1206 50V X7R
1 × 1μF 1206 50V X7R
1 × 1μF 0805 50V X7R
1 × 1μF 0805 50V X7R
220
2 × 10μF 0805 6.3V X7R
2 × 10μF 0805 6.3V X7R
1 × 10μF 0805 6.3V X7R
1 × 10μF 0805 6.3V X7R
1 × 10μF 0805 6.3V X7R
1 × 10μF 0805 6.3V X7R
1 × 10μF 0805 6.3V X7R
1 × 10μF 0805 10V X7R
1.2
1.5
1.8
2.5
3.3
5
220
300
300
400
600
600
700
49.9
49.9
49.9
49.9
158
49.9
70
261
49.9
5.5
60
294
49.9
Transient Protection
In applications where fast line transients or oscilla-
tions with a slew rate in excess of 15V/µs are expect-
ed during power-up or steady-state operation, the
MAXM17900 should be protected with a series resistor
that forms a low pass filter with the input ceramic capacitor
(Figure 4). These transients can occur in conditions such
as hot-plugging from a low-impedance source or due to
inductive load switching and surges on the supply lines.
4.7Ω
IN
MAXM17900
C
IN
=2.2µF
GND
Power Dissipation
Ensure that the junction temperature of the devices do
not exceed 125°C under the operating conditions speci-
fied for the power supply. At a particular operating condi-
tion, the power losses that lead to temperature rise of the
device are estimated as follows:
Figure 4. Circuit for Transient Protection
measure the efficiency to determine the total power
dissipation. The junction temperature (T ) of the device
J
1
can be estimated at any ambient temperature (T ) from
A
P
= P
(
−1)
LOSS
OUT
η
the following equation:
P
= V
×I
OUT OUT
OUT
T = T + θ ×P
LOSS
J
A
JA
where P
is the output power, η is the efficien-
OUT
where θ is the junction-to-ambient thermal impedance
of the package.
JA
cy of power conversion. See the Typical Operating
Characteristics for the power-conversion efficiency or
Maxim Integrated
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MAXM17900
4V to 24V, 100mA,
Compact Step-Down Power Module
● Ensure that all feedback connections are short and
PCB Layout Guidelines
direct
Careful PCB layout (Figure 5) is critical to achieve clean
and stable operation. The switching power stage requires
particular attention. Follow these guidelines for a good
PCB layout:
● Route high-speed switching node (LX) away from the
signal pins
For a sample PCB layout that ensures the first-pass success,
refer to the MAXM17900 evaluation kit data sheet.
● Place the input ceramic capacitor as close as
possible to IN and GND pins
V
IN
V
OUT
OUT
IN
C
MAXM17900
IN
R1
R2
R6
C
OUT
R4
LX
RESET
EN/UVLO
FB
SS
RT/SYNC
R5
GND
MODE
R3
CIN
V
PLANE
IN
GND PLANE
+
LX
1
2
10
9
IN
R1
MAXM17900
GND
EN/UVLO
RT/SYNC
R3
R2
MODE
3
4
8
RESET
R6
7
COUT
SS
OUT
5
6
FB
R5
R4
V
OUT
PLANE
GND PLANE
VIAS TO BOTTOM SIDE GROUND PLANE
Figure 5. Layout Guidelines
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MAXM17900
4V to 24V, 100mA,
Compact Step-Down Power Module
Ordering Information
PART
TEMP RANGE
PIN-PACKAGE
10-pin uSLIC
10-pin uSLIC
MAXM17900AMB+
MAXM17900AMB+T
-40°C to +125°C
-40°C to +125°C
+Denotes a lead(Pb)-free/RoHS-compliant package.
T = Tape and reel.
Chip Information
PROCESS: BiCMOS
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MAXM17900
4V to 24V, 100mA,
Compact Step-Down Power Module
Revision History
REVISION
NUMBER
REVISION
DATE
PAGES
CHANGED
DESCRIPTION
0
12/17
Initial release
—
Updated the title, General Description, Applications, Benefits and Features,
Absolute Maximum Ratings, and Detailed Description sections; added the MODE
section, new TOC05–08, TOC16 and TOC21–22, and renumbered remaining
TOCs; updated the Package Information, Electrical Characteristics, Pin Description,
Ordering Information tables, and Table 1; Replaced the Typical Application Circuit,
Functional Diagram, Pin Configuration, and Figure 5
1
7/18
1–16
Updated the Absolute Maximum Ratings, Electrical Characteristics, Pin Description,
and Reset Output (RESET) sections
2
3
12/19
11/20
2, 4, 9, 12
14–15
Updated Table 1 and the PCB Layout Guidelines section
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.
2020 Maxim Integrated Products, Inc.
│ 17
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