19-5844; Rev 0; 5/11
MAX16977
36V, 2A, 2.2MHz Step-Down Converter
with Low Operating Current
General Description
The MAX16977 is a 2A, current-mode, step-down con-
verter with an integrated high-side switch. The device is
designed to operate with input voltages from 3.5V to 36V
while using only 30FA quiescent current at no load. The
switching frequency is adjustable from 1MHz to 2.2MHz
by an external resistor and can be synchronized to an
external clock. The output voltage is pin selectable to
be 5V fixed or adjustable from 1V to 10V. The wide input
voltage range along with its ability to operate at high duty
cycle during undervoltage transients make the device
ideal for automotive and industrial applications.
The device operates in skip mode for reduced current
consumption in light-load applications. Protection features
include overcurrent limit, overvoltage, and thermal shut-
down with automatic recovery. The device also features
a power-good monitor to ease power-supply sequencing.
The device operates over the -40NC to +125NC automo-
tive temperature range, and is available in 16-pin TSSOP
and TQFN (5mm x 5mm) packages with exposed pads.
S
42V Input Transients Tolerance
S
High Duty Cycle During Undervoltage Transients
S
5V Fixed or 1V to 10V Adjustable Output Voltage
S
Integrated 2A Internal High-Side (70mI typ)
Switch
S
Fast Load-Transient Response and Current-Mode
Architecture
S
Adjustable Switching Frequency (1MHz to 2.2MHz)
S
Frequency Synchronization Input
S
30µA Standby Mode Operating Current
S
5µA Typical Shutdown Current
S
Spread Spectrum (Optional)
S
Overvoltage, Undervoltage, Overtemperature, and
Short-Circuit Protections
Features
S
Wide 3.5V to 36V Input Voltage Range
Applications
Automotive
Industrial/Military
High-Voltage Input DC-DC Converters
Point-of-Load Applications
Ordering Information
appears at end of data sheet.
For related parts and recommended products to use with this part,
refer to:
www.maxim-ic.com/MAX16977.related
Typical Application Circuit
V
BAT
C
IN1
47µF
C
IN2
4.7µF
SUP
EN
FSYNC
COMP
C
COMP2
12pF
R
FOSC
12kI
FOSC
FB
SUPSW
BST
LX
C
BST
0.1µF
L1
2.2µH
D1
V
BIAS
V
BIAS
R
PGOOD
10kI
POWER GOOD
V
OUT
5V AT 2A
C
OUT
22µF
V
OUT
MAX16977
C
COMP1
2.2nF
R
COMP
20kI
OUT
C
BIAS
1µF
BIAS
GND
PGOOD
½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½
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.
MAX16977
36V, 2A, 2.2MHz Step-Down Converter
with Low Operating Current
ABSOLUTE MAXIMUM RATINGS
SUP, SUPSW, LX, EN to GND ...............................-0.3V to +42V
SUP to SUPSW .....................................................-0.3V to +0.3V
BST to GND ...........................................................-0.3V to +47V
BST to LX ...............................................................-0.3V to +6V
OUT to GND ..........................................................-0.3V to +12V
FOSC, COMP, BIAS, FSYNC, I.C.,
PGOOD,
FB to GND............................................................-0.3V to +6V
LX Continuous RMS Current ...................................................3A
Output Short-Circuit Duration ....................................Continuous
*As
per the JEDEC 51 standard (multilayer board).
Continuous Power Dissipation (T
A
= +70NC)
TSSOP (derate 26.1mW/
o
C above +70
o
C) .......... 2088.8mW*
TQFN (derate 28.6mW/
o
C above +70
o
C) ............ 2285.7mW*
Operating Temperature Range ........................ -40NC to +125NC
Junction Temperature .....................................................+150NC
Storage Temperature Range............................ -65NC to +150NC
Lead Temperature (soldering, 10s) ................................+300NC
Soldering Temperature (reflow) ..................................... +260
o
C
PACKAGE THERMAL CHARACTERISTICS (Note 1)
TSSOP
Junction-to-Ambient Thermal Resistance (B
JA
) .......38.3NC/W
Junction-to-Case Thermal Resistance (B
JC
) .................3NC/W
TQFN
Junction-to-Ambient Thermal Resistance (B
JA
) ..........35NC/W
Junction-to-Case Thermal Resistance (B
JC
) ..............2.7NC/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.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 opera-
tion 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
(V
SUP
= V
SUPSW
= 14V, V
EN
= 14V, C
BIAS
= 1FF, R
FOSC
= 12kI, T
A
= T
J
= -40NC to +125NC, unless otherwise noted. Typical values
are at T
A
= +25NC.)
PARAMETER
Supply Voltage Range
Load-Dump Event Supply
Voltage
SYMBOL
V
SUP
,
V
SUPSW
V
SUP_LD
I
SUP
Supply Current
t
LD
< 1s
I
LOAD
= 1.5A
Standby mode, no load, V
OUT
= 5V
I
SUP_STANDBY
Standby mode, no load, V
OUT
= 5V,
T
A
= +25°C
I
SHDN
V
BIAS
V
UVBIAS
V
EN
= 0V
V
SUP
= V
SUPSW
= 6V to 36V
V
BIAS
rising
4.7
2.9
3.5
30
30
5
5
3.1
400
+175
15
60
45
12
5.3
3.3
FA
FA
V
V
mV
NC
NC
CONDITIONS
MIN
3.5
TYP
MAX
36
42
UNITS
V
V
mA
Shutdown Supply Current
BIAS Regulator Voltage
BIAS Undervoltage Lockout
BIAS Undervoltage-Lockout
Hysteresis
Thermal Shutdown Threshold
Thermal-Shutdown Threshold
Hysteresis
½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½
Maxim Integrated Products
2
MAX16977
36V, 2A, 2.2MHz Step-Down Converter
with Low Operating Current
ELECTRICAL CHARACTERISTICS (continued)
(V
SUP
= V
SUPSW
= 14V, V
EN
= 14V, C
BIAS
= 1FF, R
FOSC
= 12kI, T
A
= T
J
= -40NC to +125NC, unless otherwise noted. Typical values
are at T
A
= +25NC.)
PARAMETER
OUTPUT VOLTAGE (OUT)
Output Voltage
Skip-Mode Output Voltage
Adjustable Output Voltage
Range
Load Regulation
Line Regulation
BST Input Current
LX Current Limit
Skip-Mode Threshold
Spread Spectrum
Power-Switch On-Resistance
High-Side Switch Leakage
Current
TRANSCONDUCTANCE AMPLIFIER (COMP)
FB Input Current
I
FB
V
FB
FB connected to an external resistive
divider; 0°C < T
A
< +125°C
FB connected to an external resistive
divider; -40°C < T
A
< +125°C
6V < V
SUP
< 36V
V
FB
= 1V, V
BIAS
= 5V (Note 2)
0.99
0.985
10
1.0
1.0
0.02
900
80
f
SW
= 2.2MHz
f
SW
= 1MHz
R
FOSC
= 12kI
T
A
at +25°C
t
FSYNC
(Note 2)
V
FSYNC_HI
V
FSYNC
rising
f
OSC
+
10%
1.4
1
2.05
98
99
2.20
2.35
1
1.01
V
1.015
%/V
FS
ns
%
nA
R
ON
I
BST_ON
I
LX
I
SKIP_TH
Spread spectrum enabled
R
ON
measured between SUPSW and LX,
I
LX
= 1A, V
BIAS
= 5V
V
SUP
= 36V, V
LX
= 0V, T
A
= +25°C
V
OUT
V
OUT_SKIP
V
OUT_ADJ
V
FB
= V
BIAS
, normal operation
No load, V
FB
= V
BIAS
FB connected to external resistive divider
V
FB
= V
BIAS
, 30mA < I
LOAD
< 2A
V
FB
= V
BIAS
, 6V < V
SUPSW
< 36V
High-side on, V
BST
- V
LX
= 5V
(Note 2)
2.4
4.925
4.925
1
0.5
0.02
1.5
3
300
6
70
150
1
2.5
4
5
5
5.075
5.15
10
V
V
V
%
%/V
mA
A
mA
%
mI
FA
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
FB Regulation Voltage
FB Line Regulation
Transconductance (from FB to
COMP)
Minimum On-Time
Maximum Duty Cycle
OSCILLATOR FREQUENCY
Oscillator Frequency
EXTERNAL CLOCK INPUT (FSYNC)
FSYNC Input Current
External Input Clock Acquisition
Time
External Input Clock Frequency
External Input Clock
High Threshold
DV
LINE
g
m
t
ON_MIN
DC
MAX
MHz
FA
Cycles
Hz
V
½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½
Maxim Integrated Products
3
MAX16977
36V, 2A, 2.2MHz Step-Down Converter
with Low Operating Current
ELECTRICAL CHARACTERISTICS (continued)
(V
SUP
= V
SUPSW
= 14V, V
EN
= 14V, C
BIAS
= 1FF, R
FOSC
= 12kI, T
A
= T
J
= -40NC to +125NC, unless otherwise noted. Typical values
are at T
A
= +25NC.)
PARAMETER
External Input Clock
Low Threshold
Soft-Start Time
ENABLE INPUT (EN)
Enable Input-High Threshold
Enable Input-Low Threshold
Enable Threshold Voltage
Hysteresis
Enable Input Current
RESET
Output Overvoltage Trip
Threshold
PGOOD
Switching Level
PGOOD
Debounce
PGOOD
Output Low Voltage
PGOOD
Leakage Current
I
SINK
= 5mA
V
OUT
in regulation, T
A
= +25NC
V
OUT_OV
VTH_RISING
SYMBOL
V
FSYNC_LO
t
SS
V
EN_HI
V
EN_LO
V
EN,HYS
I
EN
T
A
= +25NC
CONDITIONS
V
FSYNC
falling
MIN
TYP
MAX
0.4
UNITS
V
ms
V
8.5
2
0.9
0.2
1
V
V
FA
105
V
FB
rising, V
PGOOD
= high
V
FB
falling, V
PGOOD
= low
93
90
10
110
95
92.5
35
115
97
95
60
0.4
1
%V
FB
%V
FB
Fs
V
FA
V
TH_FALLING
Note 2:
Guaranteed by design; not production tested.
½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½
Maxim Integrated Products
4
MAX16977
36V, 2A, 2.2MHz Step-Down Converter
with Low Operating Current
Typical Operating Characteristics
(V
SUP
= V
SUPSW
= 14V, V
EN
= 14V, V
OUT
= 5V, V
FSYNC
= 0V, R
FOSC
= 12.1kHz, T
A
= +25NC, unless otherwise noted.)
FULL-LOAD STARTUP BEHAVIOR
NO-LOAD STARTUP BEHAVIOR
(5V/2.2MHz)
MAX16977 toc02
MAX16977 toc01
5V/2.2MHz
RESISTIVE LOAD = 2.5Ω
V
IN
5V/div
V
IN
SUP SHORTED TO SUPSW
5V/div
0V
2V/div
V
OUT
0V
2V/div
0V
10V/div
0V
V
OUT
I
LOAD
V
PGOOD
2ms/div
0V
1A/div
0A
5V/div
0V
V
PGOOD
2ms/div
SUPPLY CURRENT vs. SUPPLY VOLTAGE
(5V/2.2MHz)
MAX16977 toc03
EFFICIENCY vs. LOAD CURRENT
(V
IN
= 14V)
MAX16977 toc04
EFFICIENCY vs. LOAD CURRENT
(V
IN
= 14V)
95
90
EFFICIENCY (%)
85
80
75
70
65
60
55
50
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0
D1: B360B-13-F FROM DIODES, INC.
L1: WURTH 744311220
8V
3.3V
5V
SUPPLY CURRENT (µA)
90
80
70
60
50
40
30
20
10
0
3.3V
8V
5V
I
SUP
+ I
SUPSW
5.5 9.0 12.5 16.0 19.5 23.0 26.5 30.0 33.5
SUPPLY VOLTAGE (V)
f
SW
= 2.2MHz
L1 = 2.2µH (WURTH 744311220)
D1: D360B-13-F FROM DIODES, INC.
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
I
LOAD
(A)
0.0001
0.001
0.01
0.1
LOAD CURRENT (A)
SWITCHING FREQUENCY vs. R
FOSC
MAX16977 toc06
SWITCHING FREQUENCY vs. LOAD CURRENT
(5V/2.2MHz)
V
IN
= 14V
MAX16977 toc07
3.0
SWITCHING FREQUENCY (MHz)
2.5
2.0
1.5
1.0
0.5
0
12
15
18
R
FOSC
(k
I
)
21
3.0
SWITCHING FREQUENCY (MHz)
2.5
2.0
1.5
1.0
0.5
0
0
V
IN
= 14V
I
LOAD
= 1.5A
24
0.5
1.0
I
LOAD
(A)
1.5
2.0
½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½½
Maxim Integrated Products
5
MAX16977 toc05
120
110
100
100
100
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