MAX16961
3A, 2.2MHz, Synchronous Step-Down
DC-DC Converter
General Description
The MAX16961 is a high-efficiency, synchronous stepdown converter that operates with a 2.7V to 5.5V input
voltage range and provides a 0.8V to 3.6V output voltage
range. The wide input/output voltage range and the ability
to provide up to 3A to load current make this device ideal
for on-board point-of-load and post-regulation applications. The device achieves -3.7%/+2.6% output error over
load, line, and temperature ranges.
The device features a 2.2MHz fixed-frequency PWM
mode for better noise immunity and load transient
response, and a pulse-frequency modulation mode
(skip) for increased efficiency during light-load operation.
The 2.2MHz frequency operation allows for the use of allceramic capacitors and minimizes external components.
The optional spread-spectrum frequency modulation
minimizes radiated electromagnetic emissions.
Integrated low RDSON switches improve efficiency at
heavy loads and make the layout a much simpler task
with respect to discrete solutions.
The device can be offered with factory-preset output voltages, or with an adjustable output voltage (contact factory
for preset output-voltage options). Factory-preset outputvoltage versions allow customers to achieve -3.7%/+2.6%
output-voltage accuracy without using external resistors,
while the adjustable output-voltage version provides the
flexibility to set the output voltage to any desired value
between 0.8V to 3.6V using an external resistive divider.
Benefits and Features
S Small External Components
2.2MHz Operating Frequency
S Ideal for Point-of-Load Applications
3A Maximum Load Current
Adjustable Output Voltage: 0.8V to 3.6V
2.7V to 5.5V Operating Supply Voltage
S High Efficiency at Light Load
26µA Skip Mode Quiescent Current
S Minimizes Electromagnetic Interference
Programmable SYNC I/O Pin
Operates Above AM-Radio Band
Available Spread Spectrum
S Low Power Mode Saves Energy
1µA Shutdown Current
S Open-Drain Power-Good Output
S Limits Inrush Current During Startup
Soft-Start
S Overtemperature and Short-Circuit Protections
S 16-Pin TSSOP-EP and 16-Pin (4mm x 4mm)
TQFN-EP Packages
S -40°C to 125°C Operating Temperature Range
Applications
Automotive Infotainment
Point-of-Load Applications
Additional features include 8ms soft-start, 16ms powergood output delay, overcurrent, and overtemperature
protections.
The MAX16961 is available in thermally enhanced
16-pin TSSOP-EP and 16-pin (4mm x 4mm) TQFN-EP
packages, and is specified for operation over the -40NC
to +125NC automotive temperature range.
Industrial/Military
Typical Application Circuit
VPV1
PV1
4.7µF
OUTS
0.47µH
PV2
Ordering Information appears at end of data sheet.
EN
LX2
PGND1
VPV
PGND2
10Ω
PV
1µF
GND
VOUT1
LX1
MAX16961
EP
47µF
VOUT1
20kΩ
PG
For pricing, delivery, and ordering information, please contact Maxim Direct
at 1-888-629-4642, or visit Maxim’s website at www.maximintegrated.com.
19-6520; Rev 5; 7/15
MAX16961
3A, 2.2MHz, Synchronous Step-Down
DC-DC Converter
ABSOLUTE MAXIMUM RATINGS
PV, PV1, PV2 to GND...............................................-0.3V to +6V
EN, PG to GND........................................................-0.3V to +6V
PGND1 and PGND2 to GND ...............................-0.3V to +0.3V
LX1, LX2 Continuous RMS Current
(LX1 connected in Parallel with LX2)....................................4A
LX Current (LX1 connected in Parallel with LX2).....Q6A (Note 5)
All Other Pins Voltages to GND... (VPV + 0.3V) to (VGND - 0.3V)
Output Short-Circuit Duration.....................................Continuous
Continuous Power Dissipation (TA = +70NC)
TQFN (derate 25mW/NC above +70NC)................... 2000mW*
TSSOP (derate 26.1mW/NC above +70NC)........... 2088.8mW*
Operating Temperature Range......................... -40NC to +125NC
Junction Temperature......................................................+150NC
Storage Temperature Range............................. -65NC to +150NC
Lead Temperature (soldering, 10s).................................+300NC
Soldering Temperature (reflow).......................................+260NC
*As per JEDEC51 Standard (multilayer board).
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 THERMAL CHARACTERISTICS (Note 1)
TQFN
Junction-to-Ambient Thermal Resistance (BJA)...........40NC/W
Junction-to-Case Thermal Resistance (BJC)..................6NC/W
TSSOP
Junction-to-Ambient Thermal Resistance (BJA).....38.3NC/W
Junction-to-Case Thermal Resistance (BJC)...............3NC/W
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.maximintegrated.com/thermal-tutorial.
ELECTRICAL CHARACTERISTICS
(VPV = VPV1 = VPV2 = 5V, VEN = 5V, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 2)
PARAMETER
Supply Voltage Range
Supply Current
Shutdown Supply Current
SYMBOL
CONDITIONS
MIN
VPV
Normal operation
2.7
IPV
No load, VPWM = 0V
12
ISHDN
Undervoltage-Lockout Threshold
Low
VUVLO_L
Undervoltage-Lockout Threshold
High
VUVLO_H
VEN = 0V, TA = +25°C
TYP
MAX
UNITS
5.5
V
26
45
FA
1
5
FA
2.37
V
2.6
Undervoltage-Lockout Hysteresis
V
0.07
V
800
mV
SYNCHRONOUS STEP-DOWN DC-DC CONVERTER
FB Regulation Voltage
VOUTS
Feedback Set-Point Accuracy
VOUTS
ILOAD = 4A
-3
0
+3
ILOAD = 0A
-0.5
+2
+3
%
pMOS On-Resistance
RDSON_P
VPV1 = 5V, ILX_ = 0.4A,
LX1 in parallel with LX2
34
55
mI
nMOS On-Resistance
RDSON_N
VPV1 = 5V, ILX_ = 0.8A,
LX1 in parallel with LX2
25
45
mI
5.1
6.3
A
Maximum pMOS Current-Limit
Threshold
Maxim Integrated
ILIMP1
LX1 and LX2 shorted together
3.9
2
MAX16961
3A, 2.2MHz, Synchronous Step-Down
DC-DC Converter
ELECTRICAL CHARACTERISTICS (continued)
(VPV = VPV1 = VPV2 = 5V, VEN = 5V, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 2)
PARAMETER
Maximum Output Current
SYMBOL
IOUT
OUTS Bias Current
IB_OUTS
LX_ Leakage Current
ILX_LEAK
Minimum On-Time
tON_MIN
LX Discharge Resistance
RLX
CONDITIONS
(VOUT + 0.5V P VPV1 P 5.5V) (Note 3)
MIN
TYP
MAX
3.3
UNITS
A
Fixed output voltage variants
1
Adjustable output version
-1
2
+1
5
VPV_ = 5V, LX_ = PGND_ or PV_,
TA = +25°C
-1
+1
VEN = 0V, through the OUTS pin
15
60
24
Maximum Short-Circuit Current
FA
FA
ns
55
I
7.8
A
2.4
MHz
2.4
MHz
OSCILLATOR
Oscillator Frequency
Spread Spectrum
SYNC Input Frequency Range
fSW
Internally generated
Df/f
Spread spectrum enabled
fSYNC
50% duty cycle (Note 4)
2.0
2.2
+6
1.7
%
THERMAL OVERLOAD
Thermal-Shutdown Threshold
+165
°C
Thermal-Shutdown Hysteresis
15
°C
POWER-GOOD OUTPUT (PG)
PG Overvoltage Threshold
PGOVTH
Percentage of nominal output
106
110
114
%
PG Undervoltage Threshold
PGUVTH
Percentage of nominal output
90
92
94
%
PG Timeout Period
16
ms
Undervoltage-/OvervoltagePropagation Delay
28
Fs
Output High Leakage Current
PG Output Low Voltage
TA = +25°C
0.2
ISINK = 3mA
0.4
VPV = 1.2V, ISINK = 100FA
0.4
FA
V
ENABLE INPUTS (EN)
Input Voltage High
VINH
Input rising
Input Voltage Low
VINL
Input falling
2.4
Input Hysteresis
V
0.5
V
0.85
V
Input Current
VEN = high
0.1
1.0
2
FA
Pulldown Resistor
VEN = low
50
100
200
kI
DIGITAL INPUTS (PWM, SYNC AS INPUT)
Input Voltage High
VINH
Input Voltage Low
VINL
1.8
0.4
Input Voltage Hysteresis
Pulldown Resistor
Maxim Integrated
V
50
50
100
V
mV
200
kI
3
MAX16961
3A, 2.2MHz, Synchronous Step-Down
DC-DC Converter
ELECTRICAL CHARACTERISTICS (continued)
(VPV = VPV1 = VPV2 = 5V, VEN = 5V, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 2)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
0.4
V
DIGITAL OUTPUT (SYNC AS OUTPUT)
Output-Voltage Low
VOL
ISINK = 3mA
Output-Voltage High
VOH
VPV = 5V, ISOURCE = 3mA
Note
Note
Note
Note
4.2
V
2: All limits are 100% production tested at +25°C. Limits over temperature are guaranteed by design.
3: Calculated value based on an assumed inductor current ripple of 30%.
4: For SYNC frequency outside (1.7, 2.4) MHz, contact factory.
5: 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.
Typical Operating Characteristics
(VPV = VPV1 = 5V, VEN = 5V, TA = +25°C, unless otherwise noted.)
VOUT = 2.5V
60
VOUT = 1.8V
40
30
50
40
VOUT = 1.8V
30
VOUT = 1.2V
20
VOUT = 3.3V
60
0.1000
1.0000
0
0.0010
10.0000
0.0100
VOUT = 1.2V
VOUT = 2.5V
40
30
VIN = 3.3V
0.0010
0.0100
0.1000
LOAD CURRENT (A)
Maxim Integrated
1.0000
MAX16961 toc03
VIN = 5V
0
10.0000
0.001
-0.50
-1.50
TA = -40°C
-2.50
1.0000 10.0000
1.000
10.000
1
VIN = 5V
VOUT = 3.3V
0
-1
-2
-3
TA = -40°C
-4
TA = +25°C
-3.50
0.100
VOUT LOAD REGULATION (SKIP)
-1.00
-2.00
0.010
LOAD CURRENT (A)
VIN = 5V
VOUT = 3.3V
-3.00
20
0
0.0001
0.1000
0
REGULATION (%)
EFFICIENCY (%)
80
10
10
0.50
MAX16961 toc04
90
50
VOUT = 1.2V
VOUT LOAD REGULATION (PWM)
EFFICIENCY vs. LOAD CURRENT (SKIP)
60
40
LOAD CURRENT (A)
100
VOUT = 1.8V
VOUT = 1.8V
50
0
ILOAD (A)
70
60
20
VOUT = 1.2V
10
0.0100
VOUT = 3.3V
70
30
20
10
0
0.0010
80
REGULATION (%)
50
70
90
MAX16961 toc05
70
80
EFFICIENCY (%)
EFFICIENCY (%)
80
VIN = 5V
90
EFFICIENCY (%)
VIN = 3.3V
100
MAX16961 toc02
MAX16961 toc01
90
EFFICIENCY vs. LOAD CURRENT (SKIP)
EFFICIENCY vs. LOAD CURRENT (PWM)
100
TA = +25°C
-5
TA = +125°C
-4.00
MAX16961 toc06
EFFICIENCY vs. LOAD CURRENT (PWM)
100
TA = +125°C
-6
0
0.5
1.0
1.5
ILOAD (A)
2.0
2.5
3.0
0
0.5
1.0
1.5
2.0
2.5
3.0
ILOAD (A)
4
MAX16961
3A, 2.2MHz, Synchronous Step-Down
DC-DC Converter
Typical Operating Characteristics
(TA = +25°C, unless otherwise noted.)
VOUT vs. VPV (PWM)
IPV vs. VPV (SKIP)
1.83
TA = -40°C
1.81
30
TA = +25°C
1.80
1.79
1.77
1.75
34
3.1
3.5
3.9
4.3
4.7
5.1
5.5
TA = -40°C
2.5
3.0
3.5
4.0
4.5
5.0
5.5
VPV (V)
VPV (V)
IPV vs. TEMPERATURE (SKIP)
LOAD-TRANSIENT RESPONSE (PWM)
MAX16961 toc10
MAX16961 toc09
VPV = 5V
VPWM = 0V
VEN1 = VPV
VOUT = 0.9V
VIN = 3.3V
3.0A
32
IPV (µA)
TA = +25°C
10
2.7
36
25
15
TA = +125°C
1.76
38
TA = +125°C
20
1.78
40
VPWM = 0V
VEN1 = VEN2 = VPV
VOUT1 = VOUT2 = 0.8V
35
IPV (µA)
VOUT (V)
1.82
MAX16961 toc08
ILOAD = 0A
1.84
40
MAX16961 toc07
1.85
0.30A
0A
ILOAD
30
28
VOUT
AC-COUPLED
26
50mV/div
24
22
20
100µs/div
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
SHDN CURRENT vs. VPV
fSW vs. TEMPERATURE
VIN = 5V
PWM MODE
2.16
100
TA = +125°C
10
2.12
SHDN (nA)
fSW (MHz)
2.14
2.10
2.08
1
0.1
2.06
2.04
TA = +25°C
0.01
2.02
TA = -40°C
0.001
2.00
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
Maxim Integrated
MAX16961 toc12
2.18
1000
MAX16961 toc11
2.20
2.5
3.0
3.5
4.0
4.5
5.0
5.5
VPV (V)
5
MAX16961
3A, 2.2MHz, Synchronous Step-Down
DC-DC Converter
SYNC
PWM
GND
TOP VIEW
PV
Pin Configurations
12
11
10
9
TOP VIEW
8
GND 13
7
GND 14
PG
OUTS
MAX16961
GND 15
EP
2
3
4
LX1
LX2
1
5
PGND1
+
PGND2
PV2 16
6
EN
PV1
GND
1
PV2
+
16
GND
2
15
GND
LX2
3
14
PV
PGND2
4
13
SYNC
PGND1
5
LX1
6
PV1
7
EN
8
MAX16961
EP
12
PWM
11
GND
10
PG
9
OUTS
TSSOP
TQFN
(4mm x 4mm)
Pin Descriptions
PIN
NAME
FUNCTION
TQFN
TSSOP
1
3
LX2
2
4
PGND2
Power Ground 2
3
5
PGND1
Power Ground 1
4
6
LX1
Switching Node 1. LX1 is high impedance when the converter is off.
5
7
PV1
Input Supply 1. Bypass PV1 with at least a 4.7FF ceramic capacitor to PGND1. Connect PV1 to
PV2 for normal operation.
6
8
EN
Enable Input. Drive EN high to enable the converter. Drive EN low to disable the converter.
7
9
OUTS
Feedback Input (Adjustable Output Option Only). Connect an external resistive divider from
VOUT to OUTS and GND to set the output voltage. See Figure 2.
8
10
PG
9,
13–15
1, 11,
15, 16
GND
Ground
10
12
PWM
PWM Control Input. Drive PWM high to put the converters in forced-PWM mode. Drive PWM low
to put the converters in skip mode.
11
13
SYNC
Factory-Set Sync Input or Output. As an input, SYNC accepts a 1.7MHz to 2.4MHz external clock
signal. As an output, SYNC outputs a 90° phase-shifted signal with respect to internal oscillator.
Maxim Integrated
Switching Node 2. LX2 is high impedance when the converter is off.
Power-Good Output. Open-drain output. PG asserts when VOUT drops below 8% or rises above
10% of the nominal output voltage. Connect to a 20kI pullup resistor.
6
MAX16961
3A, 2.2MHz, Synchronous Step-Down
DC-DC Converter
Pin Descriptions (continued)
PIN
NAME
FUNCTION
14
PV
Device Supply Voltage Input. Bypass with at least a 1FF ceramic capacitor to GND. In addition,
connect a 10I decoupling resistor between PV and the bypass capacitor.
16
2
PV2
Input Supply 2. Bypass PV2 with at least a 4.7FF ceramic capacitor to PGND2. Connect PV2 to
PV1 for normal operation.
—
—
EP
Exposed Pad. Connect EP to a large-area contiguous copper ground plane for effective power
dissipation. Do not use EP as the only IC ground connection. EP must be connected to GND.
TQFN
TSSOP
12
Detailed Description
The MAX16961 is a high-efficiency, synchronous stepdown converter that operates with a 2.7V to 5.5V input
voltage range and provides a 0.8V to 3.6V output voltage
range. The device delivers up to 3A of load current and
achieves -3.7%/+2.6% output error over load, line, and
temperature ranges.
The PWM input forces the device into either a fixedfrequency, 2.2MHz PWM mode or a low-power pulsefrequency modulation mode (skip). Optional spreadspectrum frequency modulation minimizes radiated
electromagnetic emissions due to the switching
frequency. The factory-programmable synchronization
I/O (SYNC) enables system synchronization.
Integrated low RDSON switches help improve efficiency
at heavy loads and make the layout a much simpler task
with respect to discrete solutions.
The device is offered with factory-preset output
voltages that achieve -3.7%/+2.6% output-voltage
accuracy without using external resistors. In addition, the
output voltage can be set to any desired values between
0.8V to 3.6V using an external resistive divider with the
adjustable option.
Additional features include 8ms soft-start, 16ms powergood delay output, overcurrent, and overtemperature
protections. See Figure 1.
Power-Good Output (PG)
The device features an open-drain power-good output
that asserts when the output voltage drops 8% below
or rises 10% above the regulated voltage. PG remains
asserted for a fixed 16ms timeout period after the output
rises up to its regulated voltage. Connect PG to OUTS
with a 20kI resistor.
Maxim Integrated
Soft-Start
The device includes an 8ms fixed soft-start time.
Soft-start time limits startup inrush current by forcing
the output voltage to ramp up over time towards its
regulation point.
Spread-Spectrum Option
The device featuring spread-spectrum (SS) operation
varies the internal operating frequency up by SS = 6%
relative to the internally generated operating frequency of
2.2MHz (typ). This function does not apply to externally
applied oscillation frequency. The internal oscillator is
frequency modulated with a 6% frequency deviation. See
the Selector Guide for available options.
Synchronization (SYNC)
SYNC is a factory-programmable I/O. See the Selector
Guide for available options. When SYNC is configured
as an input, a logic-high on PWM enables SYNC to
accept signal frequency in the range of 1.7MHz < fSYNC
< 2.4MHz. When SYNC is configured as an output, a
logic-high on PWM enables SYNC to output a 90N phaseshifted signal with respect to internal oscillator.
Current-Limit/Short-Circuit Protection
The device features current limit that protects the device
against short-circuit and overload conditions at the output. In the event of a short-circuit or overload condition,
the high-side MOSFET remains on until the inductor
current reaches the high-side MOSFET’s current-limit
threshold. The converter then turns on the low-side
MOSFET to allow the inductor current to ramp down.
Once the inductor current crosses the low-side MOSFET
current-limit threshold, the converter turns on the highside MOSFET for minimum on-time period. This cycle
repeats until the short or overload condition is removed.
7
MAX16961
3A, 2.2MHz, Synchronous Step-Down
DC-DC Converter
CURRENT-SENSE
AMP
PV
PV1
MAX16961
SKIP CURRENT
COMP
PV2
PV1
CLK
PEAK CURRENT
COMP
RAMP
GENERATOR
CONTROL
LOGIC
STEP-DOWN
Σ
PGND
LX1
LX2
PV
PMW
COMP
PWM
PGND
PGND2
VREF
SOFT-START
GENERATOR
ERROR
AMP
ZERO-CROSSING
COMP
FPWM CLK
PGND1
CURRENT LIM
COMP
OUTS
OSC.
SYNC
POWER-GOOD
COMP
P1-OK
FEEDBACK
DRIVER
CLK
FPWM
OTP
VOLTAGE
REFERENCE
TH-SD
P1-OK
EN
TRIM BITS
VREF
PG
MAIN
CONTROL
LOGIC
GND
Figure 1. Internal Block Diagram
FPWM/Skip Modes
The device features an input (PWM) that puts the
converter either in skip mode or forced-PWM (FPWM)
mode of operation. See the Pin Descriptions section for
mode details. In FPWM mode, the converter switches at
a constant frequency with variable on-time. In skip mode,
the converter’s switching frequency is load-dependent
until the output load reaches the skip threshold. At
higher load current, the switching frequency does not
change and the operating mode is similar to the FPWM
mode. Skip mode helps improve efficiency in light-load
applications by allowing the converters to turn on
Maxim Integrated
the high-side switch only when needed to maintain
regulation. As such, the converter does not switch
MOSFETs on and off as often as is the case in the FPWM
mode. Consequently, the gate charge and switching
losses are much lower in skip mode.
Overtemperature Protection
Thermal overload protection limits the total power dissipation in the device. When the junction temperature exceeds
+165°C (typ), an internal thermal sensor shuts down
the internal bias regulator and the step-down controller,
allowing the IC to cool. The thermal sensor turns on the IC
again after the junction temperature cools by 15°C.
8
MAX16961
3A, 2.2MHz, Synchronous Step-Down
DC-DC Converter
Table 1. Inductor Values vs. (VIN - VOUT)
VIN - VOUT (V)
5.0 to 3.3
5.0 to 2.5
5.0 to 1.5
3.3 to 0.8
INDUCTOR (µH)
0.8
0.6
0.47
0.33
Inductor Selection
VOUT
R1
C1
MAX16962
Three key inductor parameters must be specified for
operation with the MAX16961: inductance value (L),
inductor saturation current (ISAT), and DC resistance
(RDCR). Use the following formulas to determine the
minimum inductor value:
V
3
L MIN =
)×
(VIN − VOUT_ ) × ( OUT_
VIN
fOP × 3A
OUTS
R2
Figure 2. Adjustable Output Voltage Setting
Applications Information
where fOP is the operating frequency. This value is
2.2MHz unless externally synchronized to a different
frequency.
The next equation ensures that the inductor current
downslope is less than the internal slope compensation.
For this to be the case, the following equation needs to
be satisfied:
Setting the Output Voltage
Connect OUTS to VOUT for factory-programmed output voltage (see the Selector Guide). To set the output
to other voltages between 0.8V and 3.6V, connect a
resistive divider from output (VOUT) to OUTS to GND
(Figure 2). Select R2 (OUTS to GND resistor) less than
or equal to 100kI. Calculate R1 (VOUT to OUTS resistor)
with the following equation:
V
=
R1 R2 OUT − 1
V
OUTS
R1× R2
≤ 7.5kΩ
where
R1 + R2
where VOUTS = 800mV (see the Electrical Characteristics
table).
The external feedback resistive divider must be frequency
compensated for proper operation. Place a capacitor
across each resistor in the resistive-divider network.
Use the following equation to determine the value of the
capacitors:
R2
C1 = 10pF
R1
Maxim Integrated
−m ≥
m2
2
where m2 is the inductor current downslope:
VOUT
L
and -m is the slope compensation:
0.8 xIMAX
µs
Solving for L:
L MIN2
= VOUT ×
µs
1.6 × 3A
The equation that provides the bigger inductor value
must be chosen for proper operation:
LMIN = max(LMIN1, LMIN2)
The maximum inductor value recommended is twice the
chosen value from the above formula.
LMAX = 2 x LMIN
9
MAX16961
3A, 2.2MHz, Synchronous Step-Down
DC-DC Converter
The maximum inductor value must not exceed the
calculated value from the above formula. This ensures
that the current feedback loop receives the correct
amount of current ripple for proper operation.
Input Capacitor
The input filter capacitor reduces peak currents drawn
from the power source and reduces noise and voltage
ripple on the input caused by the circuit’s switching.
The input capacitor RMS current requirement (IRMS) is
defined by the following equation:
IRMS = ILOAD(MAX)
VPV1
Choose an input capacitor that exhibits less than +10NC
self-heating temperature rise at the RMS input current for
optimal long-term reliability.
The input-voltage ripple is composed of DVQ (caused
by the capacitor discharge) and DVESR (caused by the
ESR of the capacitor). Use low-ESR ceramic capacitors
with high ripple-current capability at the input. Assume
the contribution from the ESR and capacitor discharge
equal to 50%. Calculate the input capacitance and ESR
required for a specified input voltage ripple using the
following equations:
∆VESR
ESRIN =
∆I
I OUT + L
2
where:
− VOUT ) × VOUT
(V
∆IL = PV1
VPV1 × fSW × L
I
× D(1 − D)
V
CIN = OUT
and D = OUT
VPV1
∆VQ × fSW
where IOUT is the maximum output current, and D is the
duty cycle.
It is strongly recommended that a 4.7FF small footprint
be placed close to PV1 and PV2 and a minimum of 100nF
small footprint be placed close to PV. Using a small footprint such as 0805 or smaller helps to reduce the total
parasitic inductance.
Maxim Integrated
C OUT(MIN) =
=
VREF x GEAMP
2π × fCO × VOUT x R CS
0.8Vx31.7
2π × 210kHz × VOUT ×167mΩ
VOUT (VPV1 − VOUT )
IRMS has a maximum value when the input voltage
equals twice the output voltage (VPV1 = 2VOUT), so
IRMS(MAX) = ILOAD(MAX)/2.
and:
Output Capacitor
The minimum capacitor required depends on output
voltage, maximum device current capability, and the
error-amplifier voltage gain. Use the following formula to
determine the required output capacitor value:
where fCO, the target crossover frequency, is 210kHz,
GEAMP, the error-amplifier voltage gain, is 31.7V/V, and
RCS is 167mΩ.
PCB Layout Guidelines
Careful PCB layout is critical to achieve low switching
losses and clean, stable operation. Use a multilayer
board whenever possible for better noise immunity and
power dissipation. Follow these guidelines for good PCB
layout:
1) Use a large contiguous copper plane under the
device package. Ensure that all heat-dissipating
components have adequate cooling. The bottom
pad of the device must be soldered down to this
copper plane for effective heat dissipation and
maximizing the full power out of the device. Use
multiple vias or a single large via in this plane for
heat dissipation.
2) Isolate the power components and high-current path
from the sensitive analog circuitry. This is essential to
prevent any noise coupling into the analog signals.
3) Add small footprint blocking capacitors with low selfresonance frequency close to PV1, PV2, and PV.
4) Keep the high-current paths short, especially at the
ground terminals. This practice is essential for stable,
jitter-free operation. The high-current path composed
of input capacitors at PV1, PV2, inductor, and the
output capacitor should be as short as possible.
5) Keep the power traces and load connections short.
This practice is essential for high efficiency. Use
thick copper PCBs (2oz vs. 1oz) to enhance full-load
efficiency.
10
MAX16961
3A, 2.2MHz, Synchronous Step-Down
DC-DC Converter
6) OUTS is sensitive to noise for devices with external
feedback option. The resistive network (R1 and R2)
and the capacitive network (C1 and C2) must be
placed close to OUTS and far away from the LX_ node
and high switching current paths. The ground node of
R2 and C2 must be close to GND.
7) The ground connection for the analog and power
section should be close to the IC. This keeps the
ground current loops to a minimum. In cases where
only one ground is used enough isolation between
analog return signals and high power signals must be
maintained.
Chip Information
Package Information
PROCESS: BiCMOS
Maxim Integrated
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
TYPE
PACKAGE
CODE
OUTLINE
NO.
LAND
PATTERN NO.
16 TQFN-EP
T1644+4
21-0139
90-0070
16 TSSOP-EP
U16E+3
21-0108
90-0120
11
MAX16961
3A, 2.2MHz, Synchronous Step-Down
DC-DC Converter
Selector Guide
ROOT PART
MAX16961
MAX16961
MAX16961
MAX16961
PACKAGE
SUFFIX
OPTION SUFFIX
RAUE
SAUE
RATE
SATE
A/V+
A/V+
A/V+
A/V+
OUTPUT
VOLTAGE
Ext.
Ext.
Ext.
Ext.
Adj.
Adj.
Adj.
Adj.
SPREAD
SPECTRUM
SYNC IN/OUT
Disabled
Enabled
Disabled
Enabled
In
In
In
In
Note: Contact the factory for variants with different output-voltage, spread-spectrum, and power-good delay time settings.
Ordering Information
TEMP RANGE
LOAD CURRENT CAPABILITY (A)
MAX16961_ATE_/V+
PART
-40°C to +125°C
4
PIN-PACKAGE
16 TQFN-EP*
MAX16961_AUE_/V+
-40°C to +125°C
4
16 TSSOP-EP*
Note: “_” is a package suffix placeholder for either “R” or “S”, as shown in the Selector Guide. The 2nd “_” is in the option suffix.
/V denotes an automotive qualified part.
+Denotes a lead(Pb)-free/RoHS-compliant package.
*EP = Exposed pad.
Maxim Integrated
12
MAX16961
3A, 2.2MHz, Synchronous Step-Down
DC-DC Converter
Revision History
REVISION
NUMBER
REVISION
DATE
0
11/12
Initial release
—
1
4/13
Added non-automotive parts to Selector Guide
11
2
9/13
Updated input voltage high min spec and input voltage low max spec, Figure 2,
equation, step 6 in the PCB Layout Guidelines section, and the Ordering Information
3–5, 10, 11
3
5/14
Added FB regulation voltage specifications and updated VPV condition in Electrical
Characteristics table; corrected equations and updated Table 2 in the Inductor
Selection and Output Capacitor sections; updated Ordering Information
2, 3, 9–11
4
6/15
Updated General Description section to make it clear that factory needs to be
contacted for fixed output-voltage trim options
5
7/15
Added formula to equation in the Setting the Output Voltage section, replaced the
Output Capacitor section, and deleted Table 2
5.1
DESCRIPTION
Corrected revision date
PAGES
CHANGED
1
9, 10
1
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 160 Rio Robles, San Jose, CA 95134 USA 1-408-601-1000
© 2015 Maxim Integrated Products, Inc.
13
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
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