Page 1
General Description
The MAX15032 constant-frequency, pulse-width-modulating (PWM), low-noise boost converter is intended for
low-voltage systems that need a locally generated high
voltage. This device is capable of generating low-noise,
high output voltages, with an output power capability
up to 600mW with a 2.9V input voltage. This device can
be used for a wide variety of applications, such as PIN
or varactor diode biasing and LCD displays. The
MAX15032 operates from +2.7V to +11V.
The constant-frequency (500kHz), current-mode PWM
architecture provides low-noise output voltage that is
easy to filter. A high-voltage internal lateral DMOS
power switch allows this device to boost output voltages up to 36V. The MAX15032 features a shutdown
mode to save power.
The MAX15032 is available in a small thermally
enhanced 3mm x 3mm 8-pin TDFN package and is
specified for operation over the -40°C to +125°C automotive temperature range.
Applications
Avalanche Photodiode Biasing
PIN Diode Bias Supplies
Low-Noise Varactor Diode Bias Supplies
STB Audio IC Supplies
LCD Displays
Features
o Input Voltage Range
+2.7V to +5.5V (Using Internal Charge Pump)
+5.5V to +11V
o Wide Adjustable Output Voltage Range: (V
IN
+ 1V)
to 36V
o Output Power: ≥ 600mW for V
IN
≥ 2.9V
o Internal 0.5Ω (typ), 40V Switch
o Constant PWM Frequency Provides Easy Filtering
in Low-Noise Applications
o 500kHz (typ) Switching Frequency
o 0.5µA (max) Shutdown Current
o Internal Soft-Start
o Small Thermally Enhanced 3mm x 3mm 8-Pin
TDFN Package
MAX15032
500kHz, 36V Output, 600mW PWM
Step-Up DC-DC Converter
________________________________________________________________
Maxim Integrated Products
1
1
+
34
865
PGND CN IN
MAX15032
2
7
CP
LX FB SHDNGND
TDFN
TOP VIEW
Pin Configuration
Ordering Information
MAX15032
INVIN = 2.7V TO 5.5V
V
OUT
36V
SHDN
PGND
LX
FB
CP
CN
GND
R1
D1
L1
R2
C
IN
C
OUT
C
CP
Typical Operating Circuit
19-4232; Rev 0; 8/08
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
PART
TEMP RANGE
PIN-
PACKAGE
TOP
MARK
MAX15032ATA+T
-40°C to +125°C 8 TDFN-EP*
+BKP
+
Denotes a lead-free/RoHS-compliant package.
T = Tape and reel.
*
EP = Exposed pad.
Page 2
MAX15032
500kHz, 36V Output, 600mW PWM
Step-Up DC-DC Converter
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(VIN= +3.3V, V
SHDN
= +3.3V, CIN= 10µF, PGND = GND = 0V, TA= TJ= -40°C to +125°C, unless otherwise noted. Typical values
are at T
A
= +25°C. See the
Typical Operating Circuit
.) (Note 2)
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: 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.maxim-ic.com/thermal-tutorial.
IN to GND ...............................................................-0.3V to +12V
LX to PGND ............................................................-0.3V to +40V
FB to GND ..............................................................-0.3V to +12V
SHDN to GND..............................................-0.3V to (V
IN
+ 0.3V)
CN to GND .............................................................-0.3V to +12V
CP to GND..............................................................-0.3V to +12V
PGND to GND .......................................................-0.3V to +0.3V
Continuous Power Dissipation (T
A
= +70°C)
8-Pin TDFN (derate 24.4mW/°C above +70°C) ......1951.2mW
Junction-to-Case Thermal Resistance (θ
JC
) (Note 1) ........8°C/W
Junction-to-Ambient Thermal Resistance (θ
JA
)
(Note 1) ........................................................................41°C/W
Operating Temperature Range .........................-40°C to +125°C
Junction Temperature......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
SUPPLY VOLTAGE
CCP = 10nF 2.7 5.5
Supply Voltage Range V
IN
CP connected to IN 5.5 11
V
VFB = 1.4V (no switching), CCP = 10nF,
V
IN
= 3.3V
12
Supply Current I
IN
VFB = 1.4V (no switching), CP = IN,
V
IN
= 11V
1.5 3
mA
Undervoltage Lockout V
UVLO
VIN rising 2.375 2.5 2.675 V
Undervoltage Lockout Hysteresis V
UVLO-HYS
100 mV
Shutdown Current I
SHDN
V
SHDN
= 0V 0.5 µA
LOGIC INPUT (SHDN)
SHDN Input Low Level V
IL
0.8 V
SHDN Input High Level V
IH
2.0 V
BOOST CONVERTER
Output Voltage Adjustment
Range
V
IN
+ 1 36 V
Switching Frequency f
SW
450 500 550 kHz
FB Set Point V
FB
1.214 1.245 1.276 V
FB Input Bias Current I
FB
300 nA
VIN = 2.9V, VCP = 5.5V 0.42 1
CCP = 10nF,
I
LX
= 100mA
V
IN
= 5.5V, VCP = 10V 0.33 1
VIN = VCP = 5.5V 0.42 1
LX Switch On-Resistance R
DS_ON
CP connected to
IN, I
LX
= 100mA
V
IN
= VCP = 11V 0.33 1
Ω
Peak Switch Current Limit I
LIM_LX
1 1.33 1.7 A
LX Leakage Current VLX = 36V 2 µA
Line Regulation I
LOAD
= 2mA 0.25 %
Page 3
MAX15032
500kHz, 36V Output, 600mW PWM
Step-Up DC-DC Converter
_______________________________________________________________________________________ 3
Note 2: All devices are 100% production tested at room temperature (TA= +25°C). All parameter limits through the temperature
range are guaranteed by design.
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Load Regulation I
LOAD
= 0 to 20mA, V
OUT
= 30V 1 %
Soft-Start Duration 8ms
Soft-Start Steps (0.25 x I
LIM_LX
) to I
LIM_LX
32 Steps
THERMAL PROTECTION
Thermal Shutdown Rising +160 °C
Thermal-Shutdown Hysteresis 8°C
ELECTRICAL CHARACTERISTICS (continued)
(VIN= +3.3V, V
SHDN
= +3.3V, CIN= 10µF, PGND = GND = 0V, TA= TJ= -40°C to +125°C, unless otherwise noted. Typical values
are at T
A
= +25°C. See the
Typical Operating Circuit
.) (Note 2)
EFFICIENCY
vs. LOAD CURRENT
MAX15032 toc01
LOAD CURRENT (mA)
EFFICIENCY (%)
181612 144 6 8 102
40
45
50
55
60
65
70
75
80
85
35
020
V
OUT
= 36V
V
IN
= 5V
V
OUT
= 36V
V
IN
= 3.3V
EFFICIENCY
vs. LOAD CURRENT
MAX15032 toc02
LOAD CURRENT (mA)
EFFICIENCY (%)
181612 144 6 8 102
40
45
50
55
60
65
70
75
80
85
35
020
V
OUT
= 30V
V
IN
= 5V
V
OUT
= 30V
V
IN
= 3.3V
EFFICIENCY
vs. LOAD CURRENT
MAX15032 toc03
LOAD CURRENT (mA)
EFFICIENCY (%)
454030 3510 15 20 255
40
45
50
55
60
65
70
75
80
85
35
050
V
OUT
= 24V
V
IN
= 5V
V
OUT
= 24V
V
IN
= 3.3V
Typical Operating Characteristics
(VIN= 3.3V, L1 = 4.7µH, R1 = 143kΩ, R2 = 6.2kΩ, CIN= 10µF, C
OUT
= 2.2µF, CCP= 10nF, see the
Typical Operating Circuit
.
TA= +25°C, unless otherwise noted.)
Page 4
MAX15032
500kHz, 36V Output, 600mW PWM
Step-Up DC-DC Converter
4 _______________________________________________________________________________________
EFFICIENCY
vs. LOAD CURRENT
MAX15032 toc04
LOAD CURRENT (mA)
EFFICIENCY (%)
454030 3510 15 20 255
40
45
50
55
60
65
70
75
80
85
90
35
050
V
OUT
= 12V
V
IN
= 3.3V
V
OUT
= 12V
V
IN
= 5V
L = 3.3μH
MAXIMUM LOAD CURRENT
vs. INPUT VOLTAGE
MAX15032 toc05
INPUT VOLTAGE (V)
MAXIMUM LOAD CURRENT (mA)
1097 84 5 63
30
60
90
120
150
180
210
240
270
300
330
360
0
211
L = 4.7μH FOR V
OUT
= 36V, 30V, AND 24V
V
OUT
= 12V
L = 3.3μH
V
OUT
= 24V
V
OUT
= 30V
V
OUT
= 36V
MINIMUM STARTUP VOLTAGE
vs. LOAD CURRENT
MAX15032 toc06
LOAD CURRENT (mA)
MINIMUM STARTUP VOLTAGE (V)
181612 144 6 8 102
2.35
2.40
2.45
2.50
2.55
2.60
2.65
2.70
2.75
2.80
2.30
020
V
OUT
= 30V
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX15032 toc07
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (mA)
1093 4 5 76 8
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
0
211
VFB = 1.4V
SUPPLY CURRENT
vs. TEMPERATURE
MAX15032 toc08
TEMPERATURE (°C)
SUPPLY CURRENT (mA)
1109565 80-10 5 20 35 50-25
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
0.50
-40 125
VFB = 1.4V
SWITCHING FREQUENCY
vs. TEMPERATURE
MAX15032 toc09
TEMPERATURE (°C)
SWITCHING FREQUENCY (kHz)
1109565 80-10 5 20 35 50-25
460
470
480
490
500
510
520
530
540
550
450
-40 125
VIN = 5V
EXITING SHUTDOWN
MAX15032 toc10
1ms/div
V
SHDN
2V/div
V
OUT
10V/div
I
L
500mA/div
V
IN
= 5V
I
OUT
= 1mA
ENTERING SHUTDOWN
MAX15032 toc11
20ms/div
V
SHDN
2V/div
V
OUT
10V/div
V
IN
= 5V
I
OUT
= 1mA
SWITCHING WAVEFORMS
MAX15032 toc12
1μs/div
V
OUT
(AC-COUPLED)
50mV/div
V
LX
20V/div
I
L
500mA/div
I
OUT
= 20mA
Typical Operating Characteristics (continued)
(VIN= 3.3V, L1 = 4.7µH, R1 = 143kΩ, R2 = 6.2kΩ, CIN= 10µF, C
OUT
= 2.2µF, CCP= 10nF, see the
Typical Operating Circuit
.
T
A
= +25°C, unless otherwise noted.)
Page 5
MAX15032
500kHz, 36V Output, 600mW PWM
Step-Up DC-DC Converter
_______________________________________________________________________________________
5
LOAD-TRANSIENT RESPONSE
MAX15032 toc13
100ms/div
V
OUT
(AC-COUPLED)
200mV/div
I
OUT
5mA/div
RISE TIME = 10ns
LINE-TRANSIENT RESPONSE
MAX15032 toc14
2ms/div
V
IN
1V/div
V
OUT
(AC-COUPLED)
50mV/div
I
OUT
= 1mA
FB VOLTAGE
vs. TEMPERATURE
MAX15032 toc15
TEMPERATURE (°C)
FB VOLTAGE (V)
11095-25 -10 5 35 50 6520 80
1.22
1.23
1.24
1.25
1.26
1.27
1.28
1.29
1.21
-40 125
SWITCH ON-RESISTANCE
vs. TEMPERATURE
MAX15032 toc16
TEMPERATURE (°C)
SWITCH ON-RESISTANCE (mΩ)
1109565 80-10 5 20 35 50-25
450
500
550
600
650
700
750
800
850
900
950
1000
400
-40 125
VIN = 5V
LX LEAKAGE CURRENT
vs. TEMPERATURE
MAX15032 toc17
TEMPERATURE (°C)
LX LEAKAGE CURRENT (nA)
1109565 80-10 5 20 35 50-25
5
10
15
20
25
30
35
40
45
50
0
-40 125
VLX = 36V
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
MAX15032 toc18
TEMPERATURE (°C)
SHUTDOWN SUPPLY CURRENT (nA)
1109565 80-10 5 20 35 50-25
30
60
90
120
150
180
210
240
270
300
0
-40 125
V
SHDN
= 0V
OUTPUT VOLTAGE
vs. LOAD CURRENT
MAX15032 toc19
LOAD CURRENT (mA)
OUTPUT VOLTAGE (V)
181612 144 6 8 102
29.55
29.60
29.65
29.70
29.75
29.80
29.85
29.90
29.95
30.00
29.50
020
VIN = 3.3V
VIN = 5V
V
OUT
vs. OPTIMUM
INDUCTOR VALUE
MAX15032 toc20
L OPTIMUM (μH)
V
OUT
(V)
4.73.3
12
18
24
30
36
42
6
VIN = 2.7V TO 11V
Typical Operating Characteristics (continued)
(VIN= 3.3V, L1 = 4.7µH, R1 = 143kΩ, R2 = 6.2kΩ, CIN= 10µF, C
OUT
= 2.2µF, CCP= 10nF, see the
Typical Operating Circuit
.
T
A
= +25°C, unless otherwise noted.)
Page 6
MAX15032
500kHz, 36V Output, 600mW PWM
Step-Up DC-DC Converter
6 _______________________________________________________________________________________
Pin Description
PIN NAME FUNCTION
1LX
Drain of Internal 40V n-Channel DMOS. Connect inductor/diode to LX. Minimize trace area at LX to
reduce switching noise emission.
2 GND
Signal Ground. Connect directly to the local ground plane. Connect GND to PGND at a single point,
typically near the output capacitor return terminal.
3FB
Feedback Regulation Point. Connect to the center tap of a resistive divider from the output (V
OUT
) to
GND to set the output voltage. The FB voltage regulates to 1.245V (typ).
4 SHDN
Active-Low Shutdown Control Input. A logic-low voltage on SHDN shuts down the device and reduces
the supply current to 0.5µA (max). Connect SHDN to IN for always-on operation. Do not connect
SHDN to a voltage higher than V
IN
.
5 IN Input Supply Voltage. Bypass IN to PGND with a 4.7µF minimum ceramic capacitor.
6CN
Negative Terminal of the Charge-Pump Flying Capacitor for 2.7V to 5.5V Supply Voltage Operation.
Leave CN unconnected when the input voltage is in the +5.5V to +11V range.
7CP
Positive Terminal of the Charge-Pump Flying Capacitor for 2.7V to 5.5V Supply Voltage Operation.
Connect to IN when the input voltage is in the +5.5V to +11V range.
8 PGND
Power Ground. Connect the input and output filter capacitors’ negative terminal to PGND. Connect
externally to GND at a single point, typically at the output capacitor return terminal.
—EP
Exposed Pad. Connect EP to a large copper plane at the GND potential to improve thermal
dissipation. Do not use as the main GND connection.
Functional Diagram
N
MAX15032
+A
-C
-A
+C
CLK
V
REF
SHDN
V
REF
LX
PGND
FB
GND
CN
CP
IN
SWITCH
CONTROL
LOGIC
SOFTSTART
OSCILLATOR
500kHz
CHARGE
PUMP
(DOUBLER)
BIAS AND
REFERENCE
THERMAL
SHUTDOWN
SWITCH
CURRENT
SENSE
UVLO
Page 7
MAX15032
500kHz, 36V Output, 600mW PWM
Step-Up DC-DC Converter
_______________________________________________________________________________________ 7
Detailed Description
The MAX15032 constant-frequency, current-mode,
pulse-width-modulating (PWM) boost converter is
intended for low-voltage systems that often need a
locally generated high voltage. This device is capable
of generating low-noise, high-output voltage required
for PIN and varactor diode biasing and LCD displays.
The MAX15032 operates either from +2.7V to +5.5V or
from +5.5V to +11V. For +2.7V to +5.5V operation, an
internal charge pump with an external 10nF ceramic
capacitor is used. The MAX15032 also features a shutdown logic input to disable the device and reduce its
standby current to 0.5µA (max).
The MAX15032 operates in discontinuous mode in order
to reduce the switching noise caused by the reverse
recovery charge of the rectifier diode. Other continuous
mode boost converters generate large voltage spikes at
the output when the LX switch turns on because there is
a conduction path between the output, diode, and
switch to ground during the time needed for the diode to
turn off and reverse its bias voltage. To reduce the output noise even further, the LX switch turns off by taking
6.8ns typically to transition from “ON” to “OFF.” As a
consequence, the positive slew rate of the LX node is
reduced and the current from the inductor does not
“force” the output voltage as hard as would be the case
if the LX switch were to turn off more quickly.
Also, the constant-frequency (500kHz) PWM architecture generates an output voltage ripple that is easy to
filter. A 40V lateral DMOS device used as the internal
power switch makes the device ideal for boost converters with output voltages up to 36V.
The MAX15032 can also be used in other topologies
where the PWM switch is grounded, like SEPIC and
flyback.
PWM Controller
The heart of the MAX15032 current-mode PWM controller is a BiCMOS multi-input comparator that simultaneously processes the output-error signal and switch
current signal. The main PWM comparator is direct
summing, lacking a traditional error amplifier and its
associated phase shift. The direct summing configura-
tion approaches ideal cycle-by-cycle control over the
output voltage since there is no conventional error
amplifier in the feedback path.
The device operates in PWM mode using a fixed-frequency, current-mode operation. The current-mode frequency loop regulates the peak inductor current as a
function of the output error signal. The current-mode
PWM controller is intended for discontinuous conduction mode (DCM) operation. No internal slope compensation is added to the current signal.
Shutdown (
SHDN
)
The MAX15032 features an active-low shutdown input
(SHDN). Pull SHDN low to enter shutdown. During shut-
down, the supply current drops to 0.5µA (max).
However, the output remains connected to the input
through the inductor and output rectifier, holding the
output voltage to one diode drop below VINwhen the
MAX15032 shuts down. Connect SHDN to IN for
always-on operation.
Charge Pump
At low supply voltages (+2.7V to +5.5V), an internal
charge-pump circuit and an external 10nF ceramic
capacitor double the available supply voltage in order
to drive the internal switch efficiently.
In the +5.5V to +11V supply voltage range, the charge
pump must be disabled by connecting CP to IN and
leaving CN unconnected.
Design Procedure
Setting the Output Voltage
Set the MAX15032 output voltage by connecting a
resistive divider from the output to FB to GND (see the
Typical Operating Circuit
). Select R2 (FB to GND resis-
tor) between 6kΩ and 10kΩ. Calculate R1 (V
OUT
to FB
resistor) with the following equation:
where VFB= 1.245V (see the
Electrical Characteristics
table) and V
OUT
can range from (VIN+ 1V) to +36V.
RR
V
V
OUT
FB
12 1=
⎛
⎝
⎜
⎞
⎠
⎟
⎡
⎣
⎢
⎤
⎦
⎥
−
Page 8
MAX15032
Determining Peak Inductor Current
If the boost converter remains in the discontinuous
mode of operation, then the approximate peak inductor
current, I
LPEAK
(A), is represented by the formula
below:
where TSis the period in µs, V
OUT
is the output voltage in
volts, V
IN_MIN
is the minimum input voltage in volts, I
OUT
is the output current in amperes, L is the inductor value in
µH, and η is the efficiency of the boost converter.
Determining the Inductor Value
Three key inductor parameters must be specified for
operation with the MAX15032: inductance value (L),
inductor saturation current (I
SAT
), and DC resistance
(DCR). In general, the inductor should have a saturation
current rating greater than the maximum switch peak
current-limit value (I
LIM-LX(MAX)
= 1.7A). DC series
resistance (DCR) should be below 0.1Ω for reasonable
efficiency. Due to the high switching frequency of the
MAX15032, inductors with a ferrite core or equivalent
are recommended to minimize core losses. Table 1
shows a list of vendors with 4.7µH inductor parts.
Table 1. Inductor Vendors
Use the following formula to calculate the lower bound
of the inductor value at different output voltages and
output currents. This is the minimum inductance value
for discontinuous mode operation for supplying the full
600mW output power:
where VIN(V), V
OUT
(V), and I
OUT
(A) are typical values, TS(µs) is the period, η is the efficiency, and
I
LIM-LX
is the peak LX current (A).
Calculate the optimum value of L (L
OPTIMUM
) to ensure
the full output power without reaching the boundary
between continuous conduction mode (CCM) and DCM
using the following formula:
where:
For a design in which VIN= 3.3V, V
OUT
= 30V,
I
OUT
= 20mA, η = 0.7, and TS= 2µs, (L
OPTIMUM
=
4.7µH):
L
MAX
= 10.5µH
and
L
MIN
= 3.3µH
For a worst-case scenario in which VIN= 2.9V, V
OUT
=
30V, I
OUT
= 20mA, η = 0.7, I
LIM-LX(MIN)
= 1A, and TS=
1.8µs:
L
MAX
= 9.2µH
and:
L
MIN
= 2.2µH
The choice of 4.7µH is reasonable given the worst-case
scenario above. In general, the higher the inductance,
the lower the switching noise.
Diode Selection
The MAX15032’s high switching frequency demands a
high-speed rectifier. Schottky diodes are recommended for most applications because of their fast recovery
time and low forward-voltage drop. Ensure that the
diode’s peak current rating is greater than the inductor
peak current. Also, the diode reverse breakdown voltage must be greater than V
OUT
.
Output Filter Capacitor Selection
For most applications, use a small ceramic surface-mount
output capacitor, 2.2µF or greater. To achieve low output
ripple, a capacitor with low-ESR, low-ESL, and highcapacitance value should be selected. If tantalum or
electrolytic capacitors are used to achieve high capacitance values, always add a small ceramic in parallel to
bypass the high-frequency components of the diode current. The higher ESR and ESL of electrolytic increase both
the output ripple and peak-to-peak transient voltage.
Assuming the contribution from the ESR and capacitor
LH
VVV Ts
IV
MAX
IN MIN OUT IN MIN
OUT OUT
[]
()
__
μη=
××
××
−
2
2
2
L
LH
OPTIMUM
MAX
=
[]
.μ225
LH
TI V V
I
MIN
S OUT OUT IN MIN
LIM LX
[]
()
_
μη=
×× ×
×
−
−
2
2
I
TV V I
L
LPEAK
S OUT IN MIN OUT
=
×× ×
×
−2( )
_
η
500kHz, 36V Output, 600mW PWM
Step-Up DC-DC Converter
8 _______________________________________________________________________________________
VENDOR PHONE FAX
PART NUMBER
OF 4.7µH
INDUCTOR
TDK 408-437-9585 408-437-9591
SLF7045T4R7M2R0-PF
TOKO 847-297-0070 847-699-7864 636CY-4R7M+P3
Coilcraft 800-322-2645 847-639-1469 MOS6020-472MLC
Page 9
discharge equals 50% (proportions could vary), calculate the output capacitance and ESR required for a specified ripple using the following equations:
For very low output-ripple applications, the output of the
boost converter can be followed by an RC filter to further reduce the ripple. Figure 1 shows a 10Ω, 2.2µF filter used to reduce the switching output ripple to
1mV
P-P
with a 20mA output and a ripple voltage of
400µV
P-P
with a 2mA load. The output voltage regulation resistive divider must remain connected to the
diode/output capacitor node.
X7R ceramic capacitors are stable over -40°C to
+125°C temperature range. Where the automotive temperature range is required, use X7R ceramic capacitors. X5R dielectric can be used for -40°C to +85°C
applications.
Input Capacitor Selection
Bypass IN (the input voltage pin) to PGND with a minimum 4.7µF ceramic capacitor. Depending on the supply source impedance, higher values might be needed.
Make sure that the input capacitor is close enough to
the IC to provide adequate decoupling at IN as well. If
the layout cannot achieve this, add another 0.1µF
ceramic capacitor between IN and PGND in the imme-
diate vicinity of the IC. Bulk aluminum electrolytic
capacitors might be needed to avoid chattering at low
input voltages. In the case of aluminum electrolytic
capacitors, calculate the capacitor value and ESR of
the input capacitor using the following equations:
Applications Information
Layout Considerations
Careful PCB layout is critical to achieve clean and stable operation. Protect sensitive analog grounds by
using a star ground configuration. Connect GND and
PGND together close to the device at the return terminal
of the output bypass capacitor. Do not connect them
together anywhere else. Keep all PCB traces as short
as possible to reduce stray capacitance, trace resistance, and radiated noise. Ensure that the feedback
connection to FB is short and direct. Route high-speed
switching nodes away from the sensitive analog areas.
Avoid any coupling from LX to FB node by keeping the
FB node away from the LX routing. In addition, decoupling LX and FB with a small 22pF capacitor from FB to
GND can be used. Use an internal PCB layer for GND
as an EMI shield to keep radiated noise away from the
device, feedback dividers, and bypass capacitors.
CF
VI
VV
T
IL V
VVV
ESR m
VV
VI
IN
OUT OUT
IN MIN IN
S
LPEAK OPTIMUM OUT
IN MIN OUT IN MIN
IN IN MIN
OUT OUT
[]
.()
[]
.
___
_
μ
η
η
=
×
×××
××
⎡
⎣
⎢
⎢
⎤
⎦
⎥
⎥
=
×××
×
−
−
0505Δ
Ω
ΔΔ
CF
I
V
T
IL
VV
ESR m
V
I
OUT
OUT
OUT
S
LPEAK OPTIMUM
OUT IN MIN
OUT
OUT
[]
.()
[]
.
_
μ=
×
×
⎡
⎣
⎢
⎢
⎤
⎦
⎥
⎥
=
×
−
−
0505Δ
Ω
Δ
MAX15032
500kHz, 36V Output, 600mW PWM
Step-Up DC-DC Converter
_______________________________________________________________________________________ 9
Figure 1. Typical Operating Circuit with RC Filter
MAX15032
INVIN = 2.9V TO 5.5V
V
OUT
30V
SHDN
PGND
LX
FB
CP
CN
GND
R1
143kΩ
D1
1A/40V
L1
4.7μH
R2
6.2kΩ
C
IN
10μF
C
OUT
2.2μF
C
CP
10nF
C
F
2.2μF
R
F
10Ω
Page 10
MAX15032
500kHz, 36V Output, 600mW PWM
Step-Up DC-DC Converter
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
10
____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2008 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.
Chip Information
PROCESS: BiCMOS
Package Information
For the latest package outline information and land patterns, go
to www.maxim-ic.com/packages
.
PACKAGE TYPE PACKAGE CODE DOCUMENT NO.
8 TDFN T833-2
21-0137
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