19-2622; Rev 2; 6/09
1MHz, All-Ceramic, 2.6V to 5.5V Input,
2A PWM Step-Down DC-to-DC Regulators
The MAX1951/MAX1952 high-efficiency, DC-to-DC
step-down switching regulators deliver up to 2A of output current. The devices operate from an input voltage
range of 2.6V to 5.5V and provide an output voltage
from 0.8V to VIN, making the MAX1951/MAX1952 ideal
for on-board postregulation applications. The MAX1951
total output error is less than 1% over load, line, and
temperature.
The MAX1951/MAX1952 operate at a fixed frequency of
1MHz with an efficiency of up to 94%. The high operating
frequency minimizes the size of external components.
Internal soft-start control circuitry reduces inrush current.
Short-circuit and thermal-overload protection improve
design reliability.
The MAX1951 provides an adjustable output from 0.8V
to VIN, whereas the MAX1952 has a preset output of
1.8V. Both devices are available in a space-saving 8-pin
SO package.
Features
♦ Compact 0.385in2 Circuit Footprint
♦ 10µF Ceramic Input and Output Capacitors, 2µH
Inductor for 1.5A Output
♦ Efficiency Up to 94%
♦ 1% Output Accuracy Over Load, Line, and
Temperature (MAX1951, Up to 1.5A)
♦ Guaranteed 2A Output Current
♦ Operate from 2.6V to 5.5V Supply
♦ Adjustable Output from 0.8V to VIN (MAX1951)
♦ Preset Output of 1.8V (1.5% Accuracy) (MAX1952)
♦ Internal Digital Soft-Soft
♦ Short-Circuit and Thermal-Overload Protection
Ordering Information/
Selector Guide
Applications
ASIC/DSP/µP/FPGA Core and I/O Voltages
Set-Top Boxes
PART
PINPACKAGE
TEMP RANGE
Cellular Base Stations
Networking and Telecommunications
OUTPUT
MAX1951ESA+ -40°C to +85°C 8 SO
Adj 0.8V to VIN
MAX1952ESA+ -40°C to +85°C 8 SO
Fixed 1.8V
+Denotes a lead(Pb)-free/RoHS-compliant package.
Pin Configuration
Typical Operating Circuit
OUTPUT
0.8V TO VIN, UP TO 2A
INPUT
2.6V TO 5.5V
TOP VIEW
IN
VCC
8
1
LX
MAX1951
IN
VCC
REF
2
GND
3
MAX1951
MAX1952
FB 4
7
LX
6
PGND
5
COMP
COMP
PGND
OFF
FB
REF
GND
ON
SO
OPTIONAL
________________________________________________________________ Maxim Integrated Products
1
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.
MAX1951/MAX1952
General Description
MAX1951/MAX1952
1MHz, All-Ceramic, 2.6V to 5.5V Input,
2A PWM Step-Down DC-to-DC Regulators
ABSOLUTE MAXIMUM RATINGS
IN, VCC to GND ........................................................-0.3V to +6V
COMP, FB, REF to GND .............................-0.3V to (VCC + 0.3V)
LX to Current (Note 1).........................................................±4.5A
PGND to GND .............................................Internally Connected
Continuous Power Dissipation (TA = +85°C)
8-Pin SO (derate 12.2mW/°C above +70°C)................976mW
Package Junction-to-Ambient
Thermal Resistance (θJA) (Note 2)...............................82°C/W
Package Junction-to-Case
Thermal Resistance (θJC) (Note 2) ..............................32°C/W
Operating Temperature Range
MAX195_ ESA..................................................-40°C to +85°C
Junction Temperature Range ............................-40°C to +150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Note 1: LX has internal clamp diodes to PGND and IN. Applications that forward bias these diodes should take care not to exceed
the IC’s package power dissipation limits.
Note 2: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a fourlayer board. For detailed information on package thermal considerations, refer to www.maxim-ic.com/thermal-tutorial.
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
(VIN = VCC = 3.3V, PGND = GND, FB in regulation, CREF = 0.1µF, TA = 0°C to +85°C, unless otherwise noted. Typical values are at
TA = +25°C.)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
IN AND VCC
IN Voltage Range
2.6
Supply Current
Switching with no load, LX unconnected
Shutdown Current
COMP = GND
VCC Undervoltage Lockout
Threshold
When LX starts/stops switching
5.5
V
VIN = 5.5V
6
10
mA
1.0
2.5
mA
VCC rising
0.5
2.35
VCC falling
V
2
2.25
1.96
2
0.01
2.03
0.2
V
%
0.01
0.4
%
12
22
Ω
REF
REF Voltage
REF Load Regulation
IREF = 0µA, VIN = 2.6V to 5.5V
IREF = 0 to 40µA, VIN = 2.6V to 5.5V
REF Line Regulation
IREF = 20µA, VIN = 2.6V to 5.5V
REF Shutdown Resistance
From REF to GND, COMP = GND
COMP
MAX1951
40
60
80
MAX1952
26.7
40
53.3
COMP Transconductance
From FB to COMP, VCOMP = 1.25V
COMP Clamp Voltage, Low
VIN = 2.6V to 5.5V, VFB = 1.3V
0.6
1
1.2
V
COMP Clamp Voltage, High
COMP Shutdown Resistance
VIN = 2.6V to 5.5V, VFB = 1.1V
From COMP to GND, VIN = 2V
1.97
2.15
15
2.28
30
V
Ω
COMP Shutdown Threshold
When LX starts/stops switching
0.6
1
COMP Startup Current
FB
COMP rising
COMP falling
0.17
0.4
COMP = GND
15
25
Output Voltage Range
(MAX1951)
When using external feedback resistors to drive FB
0.8
FB Regulation Voltage
(Error Amp Only)
VCOMP = 1V to 2V,
IOUT = 0 to 1.5A
VIN
V
µA
V
VIN = 2.6V to 5.5V MAX1951
0.787
0.795
0.803
VIN = 2.8V to 5.5V MAX1952
1.773
1.8
1.827
18
28
kΩ
+0.1
µA
FB Input Resistance
MAX1952
13
FB Input Bias Current
MAX1951
-0.1
2
40
µS
_______________________________________________________________________________________
V
1MHz, All-Ceramic, 2.6V to 5.5V Input,
2A PWM Step-Down DC-to-DC Regulators
(VIN = VCC = 3.3V, PGND = GND, FB in regulation, CREF = 0.1µF, TA = 0°C to +85°C, unless otherwise noted. Typical values are at
TA = +25°C.)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
266
mΩ
206
mΩ
0.24
0.35
Ω
3.1
4.5
LX
LX On-Resistance, PMOS
LX On-Resistance, NMOS
VIN = 5V
116
VIN = 3.3V
140
VIN = 2.6V
163
VIN = 5V
93
VIN = 3.3V
106
VIN = 2.6V
116
LX Current-Sense
Transimpedance
From LX to COMP, VIN = 2.6V to 5.5V
LX Current-Limit Threshold
Duty cycle = 100%, VIN = 2.6V to 5.5V
LX Leakage Current
VIN = 5.5V
LX Switching Frequency
VIN = 2.6V to 5.5V
0.85
LX Maximum Duty Cycle
VCOMP = 1.5V, LX = Hi-Z, VIN = 2.6V to 5.5V
100
LX Minimum Duty Cycle
VCOMP = 1V, VIN = 2.6V to 5.5V
0.16
High side
2.4
Low side
-0.6
VLX = 5.5V
LX = GND
10
-10
1
1.1
A
µA
MHz
%
15
%
THERMAL CHARACTERISTICS
Thermal-Shutdown Threshold
When LX starts/stops switching
TJ rising
160
TJ falling
145
°C
ELECTRICAL CHARACTERISTICS
(VIN = VCC = 3.3V, PGND = GND, FB in regulation, CREF = 0.1µF, TA = -40°C to +85°C, unless otherwise noted.) (Note 3)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
IN AND VCC
IN Voltage Range
2.6
Supply Current
Switching with no load, VIN = 5.5V
Shutdown Current
COMP = GND
VCC Undervoltage Lockout
Threshold
When LX starts/stops switching
VCC rising
VCC falling
5.5
V
10
mA
1
mA
2.5
1.95
V
REF
REF Voltage
IREF = 0µA, VIN = 2.6V to 5.5V
2.03
V
REF Load Regulation
IREF = 0 to 40µA, VIN = 2.6V to 5.5V
1.95
0.2
%
REF Line Regulation
IREF = 20µA, VIN = 2.6V to 5.5V
0.4
%
REF Shutdown Resistance
From REF to GND, COMP = GND
22
Ω
_______________________________________________________________________________________
3
MAX1951/MAX1952
ELECTRICAL CHARACTERISTICS (continued)
MAX1951/MAX1952
1MHz, All-Ceramic, 2.6V to 5.5V Input,
2A PWM Step-Down DC-to-DC Regulators
ELECTRICAL CHARACTERISTICS (continued)
(VIN = VCC = 3.3V, PGND = GND, FB in regulation, CREF = 0.1µF, TA = -40°C to +85°C, unless otherwise noted.) (Note 3)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
COMP
MAX1951
40
80
MAX1952
26.7
53.3
COMP Transconductance
From FB to COMP, VCOMP = 1.25V
COMP Clamp Voltage, Low
VIN = 2.6V to 5.5V, VFB = 1.3V
0.6
1.2
V
COMP Clamp Voltage, High
VIN = 2.6V to 5.5V, VFB = 1.1V
1.97
2.28
V
COMP Shutdown Resistance
From COMP to GND, VIN = 2V
30
Ω
COMP rising
1.2
µS
COMP Shutdown Threshold
When LX starts/stops switching
COMP Startup Current
COMP = GND
14
40
µA
Output Voltage Range
(MAX1951)
When using external feedback resistors to drive FB
0.8
VIN
V
FB Regulation Voltage
(Error Amp Only)
VCOMP = 1V to 2V, VIN = 2.6V to 5.5V
MAX1951
0.783
0.807
MAX1952
1.764
1.836
FB Input Resistance
From FB to GND
COMP falling
0.17
V
FB
V
MAX1952
10
30
kΩ
MAX1951
-0.1
+0.1
µA
LX On-Resistance, PMOS
266
mΩ
LX On-Resistance, NMOS
LX Current Sense
206
mΩ
From LX to COMP, VIN = 2.6V to 5.5V
0.16
0.35
Ω
LX Current-Limit Threshold
Duty cycle = 100%, VIN = 2.6V to 5.5V, high side
2.4
4.5
A
FB Input Bias Current
LX (Note 4)
VLX = 5.5V
10
LX Leakage Current
VIN = 5.5V
LX Switching Frequency
VIN = 2.6V to 5.5V
0.8
LX Maximum Duty Cycle
VCOMP = 1.5V, LX = Hi-Z, VIN = 2.6V to 5.5V
100
LX = GND
-10
Note 3: Specifications to -40°C are guaranteed by design and not production tested.
Note 4: The LX output is designed to provide 2.4A RMS current.
4
_______________________________________________________________________________________
1.1
µA
MHz
%
1MHz, All-Ceramic, 2.6V to 5.5V Input,
2A PWM Step-Down DC-to-DC Regulators
70
VOUT = 1.5V
50
40
30
20
1.994
VOUT = 1.8V
70
60
VOUT = 1.5V
50
40
30
VOUT = 0.8V
1.995
VOUT = 0.8V
20
10
MAX1951 toc03
80
EFFICIENCY (%)
VOUT = 2.5V
60
TA = +85°C
1.993
TA = +25°C
1.992
1.991
TA = -40°C
1.990
10
0
0
10
100
10,000
1000
1.989
10
100
LOAD CURRENT (mA)
10,000
1000
1.05
1.00
TA = +25°C
0.95
TA = -40°C
0.85
0.80
2.6
3.1
3.6
10
4.1
4.6
5.1
VOUT = 2.5V
2
1
0
-1
-2
-3
25
30
35
40
VOUT = 0.8V
VOUT = 3.3V
VOUT = 1.8V
-4
-5
-6
5.6
0
0.4
0.8
1.6
1.2
LOAD CURRENT (A)
LOAD-TRANSIENT RESPONSE
LOAD-TRANSIENT RESPONSE
MAX1951 toc06
MAX1951 toc07
OUTPUT VOLTAGE:
100mV/div,
AC-COUPLED
OUTPUT VOLTAGE:
100mV/div,
AC-COUPLED
OUTPUT CURRENT:
0.5A/div
OUTPUT CURRENT:
0.5A/div
VIN = 5V
VOUT = 2.5V
IOUT = 0.5 TO 1A
40μs/div
20
6
5
4
3
INPUT VOLTAGE (V)
0A
15
REF OUTPUT CURRENT (μA)
MAX1951 toc05
TA = +85°C
OUTPUT VOLTAGE DEVIATION (mV)
MAX1951 toc04
1.15
0.90
5
OUTPUT VOLTAGE DEVIATION
vs. LOAD CURRENT
1.20
1.10
0
LOAD CURRENT (mA)
SWITCHING FREQUENCY
vs. INPUT VOLTAGE
SWITCHING FREQUENCY (MHz)
EFFICIENCY (%)
80
VOUT = 2.5V
90
REF VOLTAGE
vs. REF OUTPUT CURRENT
REF VOLTAGE (V)
VOUT = 3.3V
90
100
MAX 1951 toc01
100
EFFICIENCY vs. LOAD CURRENT
(VCC = VIN = 3.3V)
MAX 1951 toc02
EFFICIENCY vs. LOAD CURRENT
(VCC = VIN = 5V)
VIN = 3.3V
VOUT = 1.5V
IOUT = 0.5 TO 1A
0A
40μs/div
_______________________________________________________________________________________
5
MAX1951/MAX1952
Typical Operating Characteristics
(Typical values are at VIN = VCC = 5V, VOUT = 1.5V, IOUT = 1.5A, and TA = +25°C, unless otherwise noted. See Figure 2.)
Typical Operating Characteristics (continued)
(Typical values are at VIN = VCC = 5V, VOUT = 1.5V, IOUT = 1.5A, and TA = +25°C, unless otherwise noted. See Figure 2.)
SWITCHING WAVEFORMS
SOFT-START WAVEFORMS
MAX1951 toc08
MAX1951 toc09
INDUCTOR CURRENT
1A/div
VCOMP
2V/div
0A
VLX
5V/div
0V
OUTPUT VOLTAGE
1V/div
OUTPUT VOLTAGE
10mV/div,
AC-COUPLED
VIN = 3.3V
VOUT = 1.8V
ILOAD = 1.5A
VIN = VCC = 3.3V
VOUT = 2.5V
ILOAD = 1.5A
200ns/div
1ms/div
SOFT-START WAVEFORMS
SHUTDOWN WAVEFORMS
MAX1951 toc10
MAX1951 toc11
0V
VCOMP
2V/div
0V
VLX
5V/div
VCOMP
2V/div
OUTPUT VOLTAGE
0.5V/div
VIN = VCC = 3.3V
VOUT = 2.5V
ILOAD = 1.5A
VIN = VCC = 3.3V
VOUT = 0.8V
0V
1ms/div
20μs/div
SHUTDOWN CURRENT
vs. INPUT VOLTAGE
MAX1951 toc12
1.0
0.9
SHUTDOWN CURRENT (mA)
MAX1951/MAX1952
1MHz, All Ceramic, 2.6V to 5.5V Input,
2A PWM Step-Down DC-to-DC Regulators
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
INPUT VOLTAGE (V)
6
_______________________________________________________________________________________
OUTPUT VOLTAGE
1V/div
1MHz, All-Ceramic, 2.6V to 5.5V Input,
2A PWM Step-Down DC-to-DC Regulators
PIN NAME
FUNCTION
1
VCC
Supply Voltage. Bypass VCC with 0.1µF
capacitor to ground and 10Ω resistor to IN.
2
REF
Reference Bypass. Bypass REF with 0.1µF
capacitor to ground.
3
GND
Ground
4
FB
Feedback Input. Connect FB to the output to
regulate using the internal feedback resistor
string (MAX1952). Connect an external resistordivider from the output to FB and GND to set
the output to a voltage between 0.8V and VIN
(MAX1951).
5
Regulator Compensation. Connect series RC
network from COMP to GND. Pull COMP below
COMP 0.17V to shut down the regulator. COMP =
GND when VIN is less than 2.25V (see the
Compensation and Shutdown Mode section)
6
Power Ground. Internally connected to GND.
PGND Keep power ground and signal ground planes
separate.
7
8
LX
Inductor Connection. Connect an inductor
between LX and the regulator output.
IN
Power-Supply Voltage. Input voltage range
from 2.6V to 5.5V. Bypass IN with a 10µF (min)
ceramic capacitor to GND and a 10Ω resistor
to VCC.
Detailed Description
The MAX1951/MAX1952 high-efficiency switching regulators are small, simple, DC-to-DC step-down converters
capable of delivering up to 2A of output current. The
devices operate in pulse-width modulation (PWM) at a
fixed frequency of 1MHz from a 2.6V to 5.5V input voltage
and provide an output voltage from 0.8V to VIN, making
the MAX1951/MAX1952 ideal for on-board postregulation applications. The high switching frequency allows
for the use of smaller external components, and internal
synchronous rectifiers improve efficiency and eliminate
the typical Schottky free-wheeling diode. Using the onresistance of the internal high-side MOSFET to sense
switching currents eliminates current-sense resistors,
further improving efficiency and cost. The MAX1951
total output error over load, line, and temperature (0°C
to +85°C) is less than 1%.
Controller Block Function
The MAX1951/MAX1952 step-down converters use a
PWM current-mode control scheme. An open-loop comparator compares the integrated voltage-feedback signal
against the sum of the amplified current-sense signal and
the slope compensation ramp. At each rising edge of the
internal clock, the internal high-side MOSFET turns on
until the PWM comparator trips. During this on-time, current ramps up through the inductor, sourcing current to
the output and storing energy in the inductor. The currentmode feedback system regulates the peak inductor current as a function of the output voltage error signal. Since
the average inductor current is nearly the same as the
peak inductor current (100kHz). K is related to the value of the output
capacitance (see Table 1 for values of K vs. C). Set the
error-amplifier compensation zero formed by R1 and C2
at the modulator pole frequency at maximum load. C2
is calculated as follows:
C2 = (VOUT x COUT/(R1 x IOUT(MAX))
As the load current decreases, the modulator pole also
decreases; however, the modulator gain increases
accordingly, resulting in a constant closed-loop unitygain frequency. Use the following numerical example to
calculate R1 and C2 values of the typical application
circuit of Figure 2a.
Table 1. K Value
DESCRIPTION
COUT (µF)
10
22
K
Values are for output inductance from 1.2µH
0.55 to 2.2µH. Do not use output inductors larger
0.47 than 2.2µH. Use fC = 200kHz to calculate R1.
VOUT = 1.5V
IOUT(MAX) = 1.5A
COUT = 10µF
RESR = 0.010Ω
gmEA = 60µS
______________________________________________________________________________________
1MHz, All-Ceramic, 2.6V to 5.5V Input,
2A PWM Step-Down DC-to-DC Regulators
RLOAD = VOUT/IOUT(MAX) = 1.5V/1.5 A = 1Ω
fpMOD = [1/(2π x COUT x (RLOAD + RESR)]
= [1/(2 x π ×10 ×10-6 x (1 + 0.01)] = 15.76kHz.
fzESR = [1/(2π xCOUT RESR)]
= [1/(2 x π × 10 ×10-6 × 0.01)] = 1.59MHz.
For 2µH output inductor, pick the closed-loop unity-gain
crossover frequency (f C ) at 200kHz. Determine the
power modulator gain at fC:
GMOD(fc) = gmc × RLOAD × fpMOD/fC = 4.2 × 1 ×
15.76kHz/200kHz = 0.33
then:
R1 = VO x K/(gmEA x VFB x GMOD(fc)) = (1.5 x 0.55)/
(60 ×10-6 × 0.8 × 0.33) ≈ 51.1kΩ (1%)
C2 = (VOUT × COUT)/(R × IOUT(max) )
= (1.5 × 10 × 10-6)/(51.1k × 1.5)
≈ 196pF, choose 220pF, 10%
Applications Information
PCB Layout Considerations
Careful PCB layout is critical to achieve clean and stable operation. The switching power stage requires particular attention. Follow these guidelines for good PCB
layout:
1) Place decoupling capacitors as close to the IC as
possible. Keep power ground plane (connected to
PGND) and signal ground plane (connected to
GND) separate.
2) Connect input and output capacitors to the power
ground plane; connect all other capacitors to the
signal ground plane.
3) Keep the high-current paths as short and wide as
possible. Keep the path of switching current (C1 to IN
and C1 to PGND) short. Avoid vias in the switching
paths.
4) If possible, connect IN, LX, and PGND separately to
a large copper area to help cool the IC to further
improve efficiency and long-term reliability.
5) Ensure all feedback connections are short and
direct. Place the feedback resistors as close to the
IC as possible.
6) Route high-speed switching nodes away from sensitive analog areas (FB, COMP).
Thermal Considerations
The MAX1951 uses a fused-lead 8-pin SO package with
a RTHJC rating of 32°C/W. The MAX1951 EV kit layout is
optimized for 1.5A. The typical application circuit shown
in Figure 2c was tested with the existing MAX1951 EV kit
layout at +85°C ambient temperature, and GND lead
temperature was measured at +113°C for a typical
device. The estimated junction temperature was
+138°C. Thermal performance can be further improved
with one of the following options:
1) Increase the copper areas connected to GND, LX,
and IN.
2) Provide thermal vias next to GND and IN, to the
ground plane and power plane on the back side of
PCB, with openings in the solder mask next to the
vias to provide better thermal conduction.
3) Provide forced-air cooling to further reduce case
temperature.
______________________________________________________________________________________
11
MAX1951/MAX1952
gmc = 4.2S
fSWITCH = 1MHz
MAX1951/MAX1952
1MHz, All-Ceramic, 2.6V to 5.5V Input,
2A PWM Step-Down DC-to-DC Regulators
L1
2μH
2.6V TO 5.5V
IN
R4
10Ω
C5
0.1μF
MAX1951ESA
REF
COMP
C1
10μF
R3
14.7kΩ
1%
FB
VCC
R1
51.1kΩ
GND
PGND
R2
16.9kΩ
1%
OFF
C2
220pF
ON
1.5V AT 1.5A
LX
C3
0.1μF
Q1
R5
10kΩ
C4
10μF
GND
OUTPUT
COMPONENT VALUES
VOLTAGE (V) R1 (kΩ) R2 (kΩ) R3 (kΩ) C2 (pF)
220
SHORT
OPEN
0.8
33.2
220
14.7
16.9
1.5
51.1
220
30
14
2.5
82.5
220
75
24
3.3
110
OPTIONAL
SHUTDOWN
CONTROL
Figure 2a. MAX1951 Adjustable Output Typical Application Circuit
L1
2μH
2.6V TO 5.5V
IN
R4
10Ω
C5
0.1μF
1.8V AT 1.5A
LX
MAX1952ESA-18
FB
VCC
R1
68kΩ
COMP
C1
10μF
PGND
REF
C4
10μF
GND
OFF
C2
220pF
ON
Q1
R5
10kΩ
C3
0.1μF
GND
OPTIONAL
SHUTDOWN
CONTROL
Figure 2b. MAX1952 Fixed-Output Typical Application Circuit
12
______________________________________________________________________________________
1MHz, All-Ceramic, 2.6V to 5.5V Input,
2A PWM Step-Down DC-to-DC Regulators
IN
R4
10Ω
C5
0.1μF
MAX1951ESA
GND
REF
PGND
OFF
C2
100pF
ON
Q1
R5
10kΩ
R3
12.7kΩ
1%
FB
COMP
C1
10μF
1.8V, 2A
LX
VCC
R1
100kΩ
MAX1951/MAX1952
L1
1.1μH
3.3V ±5%
C3
0.1μF
R2
10kΩ
1%
C4
22μF
GND
L1: TOKO A915AY-1R1M
C1: TAIYO YUDEN JMK316BJ106ML
C4: TAIYO YUDEN JMK325BJ226MM
OPTIONAL
SHUTDOWN
CONTROL
Figure 2c. MAX1951 Typical Application Circuit with 2A Output
______________________________________________________________________________________
13
MAX1951/MAX1952
1MHz, All-Ceramic, 2.6V to 5.5V Input,
2A PWM Step-Down DC-to-DC Regulators
Table 2. External Components List
COMPONENT (FIGURE 2)
FUNCTION
DESCRIPTION
L1
Output inductor
C1
Input filtering capacitor
10µF ±20%, 6.3V X5R capacitor
Taiyo Yuden JMK316BJ106ML or
TDK C3216X5R0J106MT
C2
Compensation capacitor
220pF ±10%, 50V capacitor
Murata GRM39X7R221K050AD or
Taiyo Yuden UMK107CH221KZ
2µH ±20% inductor
Sumida CDRH4D28-1R8 or
Toko A915AY-2R0M
C3
Reference bypass capacitor
0.1µF ±20%, 16V X7R capacitor
Taiyo Yuden EMK107BJ104MA,
TDK C1608X7R1C104K, or
Murata GRM 39X7R104K016AD
C4
Output filtering capacitor
10µF ±20%, 6.3V X5R capacitor
Taiyo Yuden JMK316BJ106ML or
TDK C3216X5R0J106MT
C5
VCC bypass capacitor
0.1µF ±20%, 16V X7R capacitor
Taiyo Yuden EMK107BJ104MA,
TDK C1608X7R1C104K, or
Murata GRM 39X7R104K016AD
R1
Loop compensation resistor
Figure 2a
R2
Feedback resistor
Figure 2a
R3
Feedback resistor
Figure 2a
R4
Bypass resistor
10Ω ±5% resistor
R5
Shutdown transistor base current bias (optional)
10kΩ ±5% resistor
Q1
Shutdown transistor (optional)
NPN bipolar junction transistor
Fairchild MMBT3904
Zetex FMMT413
Table 3. Component Suppliers
MANUFACTURER
Murata
Chip Information
PHONE
FAX
650-964-6321
650-964-8165
PROCESS: BiCMOS
Sumida
847-545-6700
847-545-6720
Taiyo Yuden
800-348-2496
847-925-0899
Package Information
TDK
847-803-6100
847-803-6296
Toko
1-800-PIK-TOKO
408-943-9790
For the latest package outline information and land patterns, go
to www.maxim-ic.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.
14
PACKAGE TYPE
PACKAGE CODE
DOCUMENT NO.
8 SO
S8-F6
21-0041
______________________________________________________________________________________
1MHz, All-Ceramic, 2.6V to 5.5V Input,
2A PWM Step-Down DC-to-DC Regulators
REVISION
NUMBER
REVISION
DATE
0
10/02
Initial release
1
8/03
Updated data sheet title, Features, Typical Operating Circuit, Detailed Description
and added Thermal Considerations section.
2
6/09
Revised Ordering Information, Electrical Characteristics, Typical Operating
Characteristics, Pin Description, and the Compensation Design section.
DESCRIPTION
PAGES
CHANGED
—
1–15
1–7, 10, 11, 14
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.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 15
© 2009 Maxim Integrated Products
Maxim is a registered trademark of Maxim Integrated Products, Inc.
MAX1951/MAX1952
Revision History
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