MAX5090AATE+ [MAXIM]
2A, 76V, High-Efficiency MAXPower Step-Down DC-DC Converters; 2A ， 76V ，高效MAXPower降压型DC -DC转换器
| 型号： | MAX5090AATE+ |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | 2A, 76V, High-Efficiency MAXPower Step-Down DC-DC Converters |
| 文件： | 总17页 (文件大小：658K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-3872; Rev 0; 3/06
2A, 76V, High-Efficiency
MAXPower Step-Down DC-DC Converters
General Description
Features
♦ Wide Input Voltage Range: 6.5V to 76V
The MAX5090A/B/C easy-to-use, high-efficiency, high-
voltage step-down DC-DC converters operate from an
input voltage up to 76V, and consume only 310µA qui-
escent current at no load. This pulse-width-modulated
(PWM) converter operates at a fixed 127kHz switching
frequency at heavy loads, and automatically switches
to pulse-skipping mode to provide low quiescent cur-
rent and high efficiency at light loads. The MAX5090
includes internal frequency compensation simplifying
circuit implementation. The device can also be syn-
chronized with external system clock frequency in a
noise-sensitive application. The MAX5090 uses an
internal low on-resistance and a high-voltage DMOS
transistor to obtain high efficiency and reduce overall
system cost. This device includes undervoltage lock-
out, cycle-by-cycle current limit, hiccup-mode output
short-circuit protection, and overtemperature shutdown.
♦ Fixed (3.3V, 5V) and Adjustable (1.265V to 11V)
Output-Voltage Versions
♦ 2A Output Current
♦ Efficiency Up to 92%
♦ Internal 0.26Ω High-Side DMOS FET
♦ 310µA Quiescent Current at No Load
♦ 19µA Shutdown Current
♦ Internal Frequency Compensation
♦ Fixed 127kHz Switching Frequency
♦ External Frequency Synchronization
♦ Thermal Shutdown and Short-Circuit Current Limit
♦ -40°C to +125°C Automotive Temperature Range
♦ 16-Pin (5mm x 5mm) Thin QFN Package
♦ Capable of Dissipating 2.67W at +70°C
The MAX5090 delivers up to 2A output current. External
shutdown is included, featuring 19µA (typ) shutdown
current. The MAX5090A/MAX5090B versions have fixed
output voltages of 3.3V and 5V, respectively, while the
MAX5090C features an adjustable 1.265V to 11V output
voltage.
Ordering Information
OUTPUT
VOLTAGE
(V)
TEMP
RANGE
PIN-
PACKAGE*
PART
The MAX5090 is available in a space-saving 16-pin thin
QFN package (5mm x 5mm) and operates over the
automotive temperature range (-40°C to +125°C).
MAX5090AATE+ -40°C to +125°C 16 TQFN-EP**
3.3
MAX5090AATE -40°C to +125°C 16 TQFN-EP**
MAX5090BATE+ -40°C to +125°C 16 TQFN-EP**
MAX5090BATE -40°C to +125°C 16 TQFN-EP**
3.3
5.0
5.0
Applications
Automotive
Industrial
Ordering Information continued at end of data sheet.
*The package code is T1655-3.
**EP = Exposed pad.
Distributed Power
+Denotes lead-free package.
Typical Operating Circuit
Pin Configuration
TOP VIEW
12
EP
11
10
9
V
IN
7.5V TO 76V
R
IN
10Ω
FB
C
IN
68µF
8
7
6
5
DRAIN 13
DRAIN 14
N.C. 15
C
BYPASS
0.47µF
V
OUT
100µH
5V/2A
V
DRAIN
IN
SS
LX
MA5090
ON/OFF
C
C
BST
0.22µF
OUT
100µF
D1
PDS5100H
SYNC
VD
BST
FB
MAX5090B
16
N.C.
SS
SYNC
SGND
C
SS
VD
0.047µF
PGND
1
2
3
4
3.3µF
TQFN
________________________________________________________________ Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
2A, 76V, High-Efficiency MAXPower Step-Down
DC-DC Converters
ABSOLUTE MAXIMUM RATINGS
(Voltages referenced to PGND, unless otherwise specified.)
V
Short-Circuit Duration………………………… ...Continuous
OUT
V
, DRAIN .............................................................-0.3V to +80V
VD Short-Circuit Duration………….............................Continuous
IN
SGND, PGND.………………………………………-0.3V to +0.3V
LX.................................................................-0.8V to (V + 0.3V)
BST ...............................................................-0.3V to (V + 10V)
BST to LX................................................................-0.3V to +10V
ON/OFF........................................................-0.3V to (V + 0.3V)
Continuous Power Dissipation (T = +70°C)*
A
IN
IN
16-Pin TQFN (derate 33.3mW/°C above +70°C) ........2.667W
Operating Junction Temperature Range...........-40°C to +125°C
Storage Temperature Range .........................…-65°C to +150°C
Junction Temperature……...……………………………….+150°C
Lead Temperature (soldering, 10s) .................................+300°C
IN
VD, SYNC ...............................................................-0.3V to +12V
SS…………………………………………………………-0.3 to +4V
FB
MAX5090A/MAX5090B…………….……… ...….-0.3V to +15V
MAX5090C................1mA (internally clamped to +2V, -0.3V)
*As per JEDEC 51 Standard Multilayer Board.
Stresses beyond those listed under "Absolute Maximum Ratings" may cause 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 maxi-
mum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(V = +12V, V
= +12V, V
= 0V, I
= 0, T = T = -40°C to +125°C, unless otherwise noted. Typical values are at
IN
ON/OFF
SYNC
OUT
A
J
T
A
= +25°C. See the Typical Operating Circuit.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
6.5
TYP
MAX UNITS
Input Voltage Range
Undervoltage Lockout
UVLO Hysteresis
V
76.0
6.45
V
V
V
IN
UVLO
UVLO
V
rising
5.70
6.17
0.5
3.3
5.0
5.0
IN
HYS
MAX5090A
MAX5090B
MAX5090B
V
V
V
= 6.5V to 76V, I
= 7.5V to 76V, I
= 0 to 2A
= 0 to 2A
3.20
4.85
3.39
5.15
IN
IN
IN
OUT
Output Voltage
V
V
OUT
OUT
= 7V to 76V, I
= 0 to 1A
4.85
5.15
OUT
Output Voltage Range
Feedback Voltage
V
MAX5090C only
MAX5090C, V = 6.5V to 76V
1.265
1.191
11.000
1.265
V
V
OUT
V
1.228
80
FB
IN
MAX5090A
MAX5090B
MAX5090C
MAX5090A
MAX5090B
MAX5090C
MAX5090A
MAX5090B
MAX5090C
MAX5090A
MAX5090B
MAX5090C
V
V
V
V
V
V
V
V
V
V
V
V
= 12V, I
= 12V, I
= 1A
= 1A
IN
IN
IN
IN
IN
IN
IN
IN
IN
IN
IN
IN
OUT
OUT
Efficiency
η
88
%
= 12V, V
= 5V, I
= 1A
88
OUT
OUT
= 6.5V to 28V
= 7V to 28V
310
310
310
310
310
310
310
310
310
19
550
550
550
570
570
570
650
650
650
45
Quiescent Supply Current
(Note 2)
I
µA
µA
Q
Q
Q
= 6.5V to 28V
= 6.5V to 40V
= 7V to 40V
Quiescent Supply Current
(Note 2)
I
I
= 6.5V to 40V
= 6.5V to 76V
= 7V to 76V
Quiescent Supply Current
(Note 2)
µA
µA
= 6.5V to 76V
Shutdown Current
I
V
= 0V, V = 14V
ON/OFF IN
SHDN
SOFT-START
Default Internal Soft-Start
Period
C
= 0
700
10
µs
SS
Soft-Start Charge Current
I
4.5
16.0
µA
SS
2
_______________________________________________________________________________________
2A, 76V, High-Efficiency MAXPower Step-Down
DC-DC Converters
ELECTRICAL CHARACTERISTICS (continued)
(V = +12V, V
= +12V, V
= 0V, I
= 0, T = T = -40°C to +125°C, unless otherwise noted. Typical values are at
IN
ON/OFF
SYNC
OUT
A
J
T
A
= +25°C. See the Typical Operating Circuit.) (Note 1)
PARAMETER
Soft-Start Reference Voltage
INTERNAL SWITCH/CURRENT LIMIT
SYMBOL
CONDITIONS
MIN
TYP
MAX UNITS
V
1.23
1.46
1.65
V
SS(REF)
Peak Switch Current Limit
Switch Leakage Current
Switch On-Resistance
PFM Threshold
I
(Note 3)
2.4
-10
3.3
5.0
+10
0.4
A
µA
Ω
LIM
I
V
= 76V, V
= 0V, V = 0V
ON/OFF LX
OL
IN
R
I
= 1A
0.26
60
DS(ON)
SWITCH
I
Minimum switch current in any cycle
1
300
mA
PFM
Minimum switch current in any cycle at T ≤ +25°C
(Note 4)
J
PFM Threshold
I
14
300
mA
nA
PFM
FB Input Bias Current
I
MAX5090C, V = 1.2V
FB
-150
+0.1
1.38
+150
B
ON/OFF CONTROL INPUT
ON/OFF Input-Voltage
Threshold
V
Rising trip point
1.180
1.546
V
ON/OFF
ON/OFF Input-Voltage
Hysteresis
V
100
10
mV
nA
HYST
ON/OFF Input Current
I
V
V
= 0V to V
ON/OFF IN
100
ON/OFF
OSCILLATOR/SYNCHRONIZATION
Oscillator Frequency
Synchronization
f
106
119
80
127
95
150
200
kHz
kHz
%
0SC
f
SYNC
Maximum Duty Cycle
SYNC High-Level Voltage
SYNC Low-Level Voltage
SYNC Minimum Pulse Width
SYNC Input Leakage
D
= 6.5V to 76V, V
≤ 11V
MAX
IN
OUT
2.0
V
0.8
350
+1
V
ns
µA
-1
INTERNAL VOLTAGE REGULATOR
Regulator Output Voltage
Dropout Voltage
VD
V
= 9V to 76V, I
= 0
7.0
7.8
0.5
10
8.4
V
V
IN
OUT
6.5V ≤ V ≤ 8.5V, I
= 15mA
IN
OUT
Load Regulation
∆VD/∆I
0 to 15mA
Ω
VD
PACKAGE THERMAL CHARACTERISTICS
Thermal Resistance
(Junction to Ambient)
θ
TQFN package (JEDEC 51)
Temperature rising
30
°C/W
JA
THERMAL SHUTDOWN
Thermal-Shutdown Junction
Temperature
T
+175
20
°C
°C
SH
Thermal-Shutdown
Hysteresis
T
HYST
Note 1: All limits at -40°C are guaranteed by design, not production tested.
Note 2: For total current consumption during switching (at no load), also see the Typical Operating Characteristics.
Note 3: Switch current at which the current-limit circuit is activated.
Note 4: Limits are guaranteed by design.
_______________________________________________________________________________________
3
2A, 76V, High-Efficiency MAXPower Step-Down
DC-DC Converters
Typical Operating Characteristics
(V = 12V, V
=12V, T = T = -40°C to +125°C, unless otherwise noted. Typical values are at T = +25°C. See the Typical
A J A
IN
ON/OFF
Operating Circuit, if applicable.)
V
vs. TEMPERATURE
V
vs. TEMPERATURE
OUT
LINE REGULATION
(MAX5090AATE, V = 3.3V)
OUT
(MAX5090BATE, V = 5V)
(MAX5090AATE, V
= 3.3V)
OUT
OUT
OUT
3.40
3.38
3.36
3.34
3.32
3.30
3.28
3.26
3.24
3.22
3.20
5.15
5.10
5.05
5.00
4.95
4.90
4.85
3.40
3.38
3.36
3.34
3.32
3.30
3.28
3.26
3.24
3.22
3.20
I
= 0
I
= 0
OUT
OUT
I
= 0
OUT
I
= 2A
OUT
I
= 2A
OUT
I
= 2A
OUT
-50 -25
0
25 50 75 100 125 150
-50 -25
0
25 50 75 100 125 150
6.5
16
26
36
46
(V)
56
66
76
AMBIENT TEMPERATURE (°C)
AMBIENT TEMPERATURE (°C)
V
IN
LOAD REGULATION
LOAD REGULATION
(MAX5090AATE, V = 3.3V)
(MAX5090BATE, V
= 5V)
OUT
OUT
3.40
3.38
3.36
3.34
3.32
3.30
3.28
3.26
3.24
3.22
3.20
5.15
5.10
5.05
5.00
4.95
4.90
4.85
5.15
5.10
5.05
5.00
V
= 76V
IN
I
= 0
OUT
V
= 76V
IN
V
= 24V
IN
V
= 24V
4.95
4.90
4.85
V
IN
= 6.5V
IN
V
= 6.5V
IN
I
= 2A
OUT
56
0.1
1
10
100
(mA)
1000
10,000
0.1
1
10
100
(mA)
1000
10,000
6.5
16
26
36
46
(V)
66
76
I
V
LOAD
I
IN
LOAD
EFFICIENCY vs. LOAD CURRENT
EFFICIENCY vs. LOAD CURRENT
OUTPUT CURRENT LIMIT vs. TEMPERATURE
(MAX5090AATE)
(MAX5090AATE, V
= 3.3V)
(MAX5090BATE, V
= 5V)
OUT
OUT
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
4.0
3.5
3.0
2.5
2.0
1.5
1.0
V
= 3.3V
OUT
5% DROP IN V
PULSED OUTPUT LOAD
OUT
V
= 6.5V
IN
V
= 6.5V
IN
V
= 12V
IN
V
= 12V
IN
V
= 24V
IN
V
= 24V
IN
V
= 48V
IN
V
= 48V
IN
V
= 76V
IN
V
= 76V
IN
0
400
800
1200
1600
2000
0
400
800
1200
1600
2000
-50 -25
0
25 50 75 100 125 150
LOAD CURRENT (mA)
LOAD CURRENT (mA)
AMBIENT TEMPERATURE (°C)
4
_______________________________________________________________________________________
2A, 76V, High-Efficiency MAXPower Step-Down
DC-DC Converters
Typical Operating Characteristics (continued)
(V = 12V, V
=12V, T = T = -40°C to +125°C, unless otherwise noted. Typical values are at T = +25°C. See the Typical
IN
ON/OFF
A
J
A
Operating Circuit, if applicable.)
OUTPUT CURRENT LIMIT vs. TEMPERATURE
(MAX5090BATE)
OUTPUT CURRENT LIMIT vs. INPUT VOLTAGE
(MAX5090BATE)
OUTPUT CURRENT LIMIT vs. INPUT VOLTAGE
(MAX5090AATE)
4.0
3.5
3.0
2.5
2.0
1.5
1.0
7.0
6.0
5.0
4.0
3.0
2.0
1.0
7.0
6.0
5.0
4.0
3.0
2.0
1.0
V
= 5V
V
= 3.3V
OUT
OUT
V
= 5V
OUT
5% DROP IN V
PULSED OUTPUT LOAD
5% DROP IN V
PULSED OUTPUT LOAD
OUT
OUT
5% DROP IN V
PULSED OUTPUT LOAD
OUT
-50 -25
0
25 50 75 100 125 150
6.5
16
26
36
46
56
66
76
6.5
16
26
36
46
56
66
76
AMBIENT TEMPERATURE (°C)
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
SHUTDOWN CURRENT vs. TEMPERATURE
(MAX5090AATE)
NO-LOAD SUPPLY CURRENT vs. INPUT VOLTAGE
NO-LOAD SUPPLY CURRENT vs. TEMPERATURE
(MAX5090AATE)
(MAX5090AATE)
30
26
22
18
14
10
600
600
V
OUT
= 3.3V
V
OUT
= 3.3V
V
= 3.3V
OUT
550
500
450
400
350
300
550
500
450
400
350
300
-50 -25
0
25 50 100 125 150 175
-50 -25
0
25 50 75 100 125 150
6.5
16
26
36
46
56
66
76
AMBIENT TEMPERATURE (°C)
AMBIENT TEMPERATURE (°C)
INPUT VOLTAGE (V)
SHUTDOWN CURRENT
vs. INPUT VOLTAGE
OUTPUT VOLTAGE
vs. INPUT VOLTAGE
LOAD-TRANSIENT RESPONSE
(MAX5090AATE)
MAX5090 toc18
45
40
35
30
25
20
15
10
5
13
11
9
V
= 3.3V
V
= 3.3V
OUT
MAX5090CATE
OUT
V
V
= 11V
= V
OUT
ON/OFF
IN
A
I
= 2A
OUT
I
= 1A
OUT
6
I
= 0A
OUT
B
3
0
0
6.5 16
26
36
46
56
66
76
5
6
7
8
9
10 11 11.5 12 12.5 13
(V)
400µs/div
A: V , 200mV/div, AC-COUPLED
INPUT VOLTAGE (V)
V
IN
OUT
B: I , 1A/div, 1A TO 2A
OUT
_______________________________________________________________________________________
5
2A, 76V, High-Efficiency MAXPower Step-Down
DC-DC Converters
Typical Operating Characteristics (continued)
(V = 12V, V
=12V, T = T = -40°C to +125°C, unless otherwise noted. Typical values are at T = +25°C. See the Typical
IN
ON/OFF
A
J
A
Operating Circuit, if applicable.)
LOAD-TRANSIENT RESPONSE
(MAX5090AATE)
LX WAVEFORMS
(MAX5090AATE)
LX WAVEFORMS
(MAX5090AATE)
MAX5090 toc20
MAX5090 toc19
MAX5090 toc21
V
OUT
= 3.3V
A
A
A
B
V = 3.3V
OUT
V
OUT
= 3.3V
B
0
B
400µs/div
4µs/div
4µs/div
A: V , 200mV/div, AC-COUPLED
OUT
B: I , 500mA/div, 0.1A TO 1A
OUT
A: SWITCH VOLTAGE (LX PIN), 20mV/div (V = 48V)
IN
A: SWITCH VOLTAGE, 20V/div (V = 48V)
IN
B: INDUCTOR CURRENT, 2A/div (I = 2A)
B: INDUCTOR CURRENT, 200mA/div (I = 75mA)
0
0
LX WAVEFORM
(MAX5090AATE)
STARTUP WAVEFORM
STARTUP WAVEFORM
(I
= 0)
(I
= 2A)
OUT
OUT
MAX5090 toc22
MAX5090 toc23
MAX5090 toc24
V
OUT
= 3.3V
A
A
B
A
B
B
C
SS
= 0.047µF
C
SS
= 0.047µF
4µs/div
4ms/div
4ms/div
A: SWITCH VOLTAGE, 20V/div (V = 48V)
IN
A: V
ON/OFF
, 2V/div
A: V
ON/OFF
, 2V/div
B: INDUCTOR CURRENT, 200mA/div (I
= 0)
B: V , 1V/div
OUT
B: V , 1V/div
OUT
OUT
PEAK SWITCH CURRENT
vs. INPUT VOLTAGE
SYNCHRONIZATION
SYNCHRONIZATION
MAX5090 toc26
MAX5090 toc27
7.0
6.0
5.0
4.0
3.0
2.0
1.0
f
= 119kHz
SYNC
MAX5090AATE
f
= 200kHz
SYNC
V
= 3.3V
OUT
5% DROP IN V
OUT
SYNC
2V/div
SYNC
2V/div
PULSED OUTPUT LOAD
LX
10V/div
LX
10V/div
6.5
16
26
36
46
56
66
76
2µs/div
1µs/div
INPUT VOLTAGE (V)
6
_______________________________________________________________________________________
2A, 76V, High-Efficiency MAXPower Step-Down
DC-DC Converters
Pin Description
PIN
1, 2
3
NAME
LX
FUNCTION
Source Connection of Internal High-Side Switch
Boost Capacitor Connection. Connect a 0.22µF ceramic capacitor from BST to LX.
BST
4
V
Input Voltage. Bypass V to SGND with a low-ESR capacitor as close to the device as possible.
IN
IN
5
VD
Internal Regulator Output. Bypass VD to PGND with a 3.3µF/10V or greater ceramic capacitor.
Synchronization Input. Connect SYNC to an external clock for synchronization. Connect to SGND to
select the internal 127kHz switching frequency.
6
7
SYNC
Soft-Start Capacitor Connection. Connect an external capacitor from SS to SGND to adjust the soft-
start time.
SS
FB
Output Sense Feedback Connection.
For fixed output voltage (MAX5090A/MAX5090B), connect FB to V
.
OUT
8
9
For adjustable output voltage (MAX5090C), use an external resistive voltage-divider to set V
regulating set point is 1.228V.
. V
OUT FB
Shutdown Control Input. Pull ON/OFF low to put the device in shutdown mode. Drive ON/OFF high for
ON/OFF
normal operation. Connect ON/OFF to V with short leads for always-on operation.
IN
10
11, 15, 16
12
SGND
N.C.
Signal Ground. SGND must be connected to PGND for proper operation.
No Connection. Not internally connected.
Power Ground
PGND
DRAIN
13, 14
Internal High-Side Switch Drain Connection
Exposed Pad. Solder EP to SGND plane to aid in heat dissipation. Do not use as the only electrical
ground connection.
—
EP
Detailed Description
R1
R2
The MAX5090 step-down DC-DC converter operates
from a 6.5V to 76V input voltage range. A unique volt-
age-mode control scheme with voltage feed-forward
and an internal switching DMOS FET provides high effi-
ciency over a wide input voltage range. This pulse-
width-modulated converter operates at a fixed 127kHz
switching frequency or can be synchronized with an
external system clock frequency. The device also fea-
tures automatic pulse-skipping mode to provide high
efficiency at light loads. Under no load, the MAX5090
consumes only 310µA, and in shutdown mode, con-
sumes only 20µA. The MAX5090 also features under-
voltage-lockout, hiccup-mode output short-circuit
protection and thermal shutdown.
V
= 1 +
x 1.38
UVLO(TH)
Set the external V
to greater than 6.45V. The
maximum recommended value for R2 is less than 1MΩ.
UVLO(TH)
ON/OFF is a logic input and can be safely driven to the
full V range. Connect ON/OFF to V for automatic
IN
IN
startup. Drive ON/OFF to ground to shut down the
MAX5090. Shutdown forces the internal power MOSFET
off, turns off all internal circuitry, and reduces the V
IN
supply current to 20µA (typ). The ON/OFF rising thresh-
old is 1.546V (max). Before any operation begins, the
voltage at ON/OFF must exceed 1.546V. The ON/OFF
input has 100mV hysteresis.
If the external UVLO threshold setting divider is not
used, an internal undervoltage-lockout feature monitors
ON/OFF/Undervoltage Lockout (UVLO)
Use the ON/OFF function to program the external UVLO
threshold at the input. Connect a resistive voltage-
the supply voltage at V and allows the operation to
IN
start when V rises above 6.45V (max). The internal
IN
divider from V to SGND with the center node to
IN
UVLO rising threshold is set at 6.17V with 0.5V hystere-
ON/OFF, as shown in Figure 1. Calculate the threshold
value by using the following formula:
sis. The V and V
voltages must be above 6.5V
ON/OFF
IN
and 1.546V, respectively, for proper operation.
_______________________________________________________________________________________
7
2A, 76V, High-Efficiency MAXPower Step-Down
DC-DC Converters
Simplified Functional Diagram
DRAIN
ON/OFF
V
IN
ENABLE
REGULATOR
(FOR ANALOG)
IREF-PFM
IREF-LIM
CPFM
CILIM
1.38V
HIGH-SIDE
CURRENT SENSE
REGULATOR
(FOR DRIVER)
VD
VREF
OSC
RAMP
CLKI
RMP
BST
SRMP
SYNC
SRAMP
MUX
SCK
SS
CLK
MIN
N
FB
RAMP
CONTROL
LOGIC
*R
H
TYPE 3
COMPENSATION
LX
x1
CPWM
EAMP
*R
L
THERMAL
SHUTDOWN
PGND
MAX5090
*R = 0Ω AND R = ∞ FOR MAX5090C
H
L
SGND
8
_______________________________________________________________________________________
2A, 76V, High-Efficiency MAXPower Step-Down
DC-DC Converters
Boost High-Side Gate Drive (BST)
Connect a flying bootstrap capacitor between LX and
BST to provide the gate-drive voltage to the high-side
n-channel DMOS switch. The capacitor is alternately
charged from the internally regulated output-voltage VD
and placed across the high-side DMOS driver. Use a
0.22µF, 16V ceramic capacitor located as close to the
device as possible.
Soft-Start (SS)
The MAX5090 provides the flexibility to externally pro-
gram a suitable soft-start time for a given application.
Connect an external capacitor from SS to SGND to use
the external soft-start. Soft-start gradually ramps up the
reference voltage seen by the error amplifier to control
the output’s rate of rise and reduce the input surge cur-
rent during startup. For soft-start time longer than 700µs,
use the following equation to calculate the soft-start
On startup, an internal low-side switch connects LX to
capacitor (C ) required for the soft-start time (t ):
SS
SS
ground and charges the BST capacitor to (VD - V
).
DIODE
Once the BST capacitor is charged, the internal low-side
switch is turned off and the BST capacitor voltage pro-
vides the necessary enhancement voltage to turn on the
high-side switch.
−6
10×10
× t
SS
C
=
SS
1.46
where t > 700µs and C is in Farads.
SS
SS
Synchronization (SYNC)
SYNC controls the oscillator frequency. Connect SYNC
to SGND to select 127kHz operation. Use the SYNC
input to synchronize to an external clock. SYNC has a
guaranteed frequency range of 119kHz to 200kHz
when using an external clock.
The MAX5090 also provides an internal soft-start
(700µs, typ) with a current source to charge an internal
capacitor to rise up to the bandgap reference voltage.
The internal soft-start voltage will eventually be pulled
up to 3.4V. The internal soft-start reference also feeds
to the error amplifier. The error amplifier takes the low-
est voltage among SS, the internal soft-start voltage,
and the bandgap reference voltage as the input refer-
When SYNC is connected to SGND, the internal clock
is used to generate a ramp with the amplitude in pro-
portion to V and the period corresponding to the
IN
internal clock frequency to modulate the duty cycle of
the high-side switch.
ence for V
.
OUT
Soft-start occurs when power is first applied and when
the device exits shutdown. The MAX5090 also goes
through soft-start when coming out of thermal-overload
If an external clock (SYNC clock) is applied at SYNC for
four cycles, the MAX5090 selects the SYNC clock. The
MAX5090 generates a ramp (SYNC ramp) with the
protection. During a soft-start, if the voltage at SS (V
)
SS
is charged up to 1.46V in less than 700µs, the
MAX5090 takes its default internal soft-start (700µs) to
ramp up as its reference. After the SS and the internal
soft-start ramp up over the bandgap reference, the
error amplifier takes the bandgap reference.
amplitude in proportion to V and the period corre-
IN
sponding to the SYNC clock frequency. The MAX5090
initially blanks the SYNC ramp for 375µs (typ) to allow
the ramp to reach its target amplitude (proportion to the
V
supply). After the SYNC blanking time, the SYNC
IN
ramp and the SYNC clock switch to the PWM controller
and replace the internal ramp and the internal clock,
respectively. If the SYNC clock is removed for three
internal clock cycles, the internal clock and the internal
ramp switch back to the PWM controller.
Thermal-Overload Protection
The MAX5090 features integrated thermal-overload
protection. Thermal-overload protection limits power
dissipation in the device, and protects the device from
a thermal overstress. When the die temperature
exceeds +175°C, an internal thermal sensor signals the
shutdown logic, turning off the internal power MOSFET,
resetting the internal soft-start and allowing the IC to
cool. The thermal sensor turns the internal power
MOSFET back on after the IC’s die temperature cools
down to +155°C, resulting in a pulsed output under
continuous thermal-overload conditions.
The minimum pulse-width requirement for the external
clock is 350ns, and if the requirement is not met, the
MAX5090 could ignore the clock as a noisy bounce.
_______________________________________________________________________________________
9
2A, 76V, High-Efficiency MAXPower Step-Down
DC-DC Converters
V
IN
6.5V TO 76V
R
IN
10Ω
C
68µF
IN
C
BYPASS
0.47µF
V
OUT
R1
R2
100µH
3.3V, 2A
V
DRAIN
IN
LX
ON/OFF
C
OUT
100µF
D1
PDS5100H
0.22µF
BST
FB
MAX5090A
SS
SYNC
SGND
0.047µF
VD
PGND
3.3µF
Figure 1. Fixed Output-Voltage Configuration
V
IN
7.5V TO 76V
R
IN
10Ω
C
68µF
IN
C
BYPASS
0.47µF
V
OUT
100µH
5.25V, 2A
V
IN
DRAIN
LX
ON/OFF
C
D1
PDS5100H
OUT
0.22µF
100µF
R
3
BST
MAX5090C
FB
SS
SYNC
0.047µF
R
4
VD
SGND
PGND
3.3µF
Figure 2. Adjustable Output-Voltage Configuration
10 ______________________________________________________________________________________
2A, 76V, High-Efficiency MAXPower Step-Down
DC-DC Converters
Thermal-overload protection is intended to protect the
Table 1. Diode Selection
MAX5090 in the event of a fault condition. For normal
DIODE PART
NUMBER
circuit operation, do not exceed the absolute maximum
V
(V)
MANUFACTURER
IN
junction temperature rating of T = +150°C.
J
B340LB
RB051L-40
MBRS340T3
MBRM560
RB095B-60
MBRD360T4
50SQ80
Diodes Inc.
Setting the Output Voltage
6.5 to 36
Central Semiconductor
ON Semiconductor
Diodes Inc.
The MAX5090A/MAX5090B have preset output volt-
ages of 3.3V and 5.0V, respectively. Connect FB to
OUT
V
for the preset output voltage (Figure 1).
The MAX5090C offers an adjustable output voltage. Set
the output voltage with a resistive divider connected
from the circuit’s output to ground (Figure 2). Connect
the center node of the divider to FB. Choose R4 less
than 15kΩ, then calculate R3 as follows:
6.5 to 56
6.5 to 76
Central Semiconductor
ON Semiconductor
IR
PDS5100H
Diodes Inc.
(V
−1.228)
1.228
rating greater than the highest expected output current.
Use a rectifier with a voltage rating greater than the
maximum expected input voltage, V . Use a low for-
IN
OUT
R3 =
x R4
ward-voltage Schottky rectifier for proper operation and
high efficiency. Avoid higher than necessary reverse-
voltage Schottky rectifiers that have higher forward-volt-
age drops. Use a Schottky rectifier with forward-voltage
The MAX5090 features internal compensation for opti-
mum closed-loop bandwidth and phase margin.
Because of the internal compensation, the output must
be sensed immediately after the primary LC.
drop (V ) less than 0.55V and 0.45V at +25°C and
F
Inductor Selection
The MAX5090 is a fixed-frequency converter with fixed
internal frequency compensation. The internal fixed
compensation assumes a 100µH inductor and 100µF
output capacitor with 50mΩ ESR. It relies on the loca-
tion of the double LC pole and the ESR zero frequency
for proper closed-loop bandwidth and the phase mar-
gin at the closed-loop unity-gain frequency. See Table
2 for proper component values. Usually, the choice of
an inductor is guided by the voltage difference
+125°C, respectively, and at maximum load current to
avoid forward biasing of the internal parasitic body
diode (LX to ground). See Figure 3 for forward-voltage
drop vs. temperature of the internal body diode of the
MAX5090. Internal parasitic body-diode conduction
may cause improper operation, excessive junction tem-
perature rise, and thermal shutdown. Use Table 1 to
choose the proper rectifier at different input voltages
and output current.
Input Bypass Capacitor
The discontinuous input current waveform of the buck
converter causes large ripple currents in the input
capacitor. The switching frequency, peak inductor cur-
rent, and the allowable peak-to-peak voltage ripple
reflecting back to the source dictate the capacitance
requirement. The MAX5090 high switching frequency
allows the use of smaller value input capacitors.
between V and V
, the required output current and
OUT
IN
the operating frequency of the circuit. However, use the
recommended inductors in Table 2 to ensure stable
operation with optimum bandwidth.
Use an inductor with a maximum saturation current rat-
ing greater than or equal to the maximum peak current
limit (5A). Use inductors with low DC resistance for a
higher efficiency converter.
The input ripple is comprised of ∆V (caused by the
Q
Selecting a Rectifier
The MAX5090 requires an external Schottky rectifier as
a freewheeling diode. Connect this rectifier close to the
device using short leads and short PC board traces.
The rectifier diode must fully conduct the inductor cur-
rent when the power FET is off to have a full rectifier
function. Choose a rectifier with a continuous current
capacitor discharge) and ∆V
(caused by the ESR of
ESR
the capacitor). Use low-ESR aluminum electrolytic
capacitors with high-ripple current capability at the input.
Assuming that the contribution from the ESR and capaci-
tor discharge is equal to 90% and10%, respectively, cal-
culate the input capacitance and the ESR required for a
specified ripple using the following equations:
______________________________________________________________________________________ 11
2A, 76V, High-Efficiency MAXPower Step-Down
DC-DC Converters
∆V
ESR
ESR
=
IN
800
∆I
2
L
I
+
OUT
700
600
500
400
300
200
100
0
I
×D(1−D)
OUT
C
=
IN
∆V × f
Q
SW
where:
(V − V
) × V
×L
IN
OUT
OUT
∆I =
L
V
× f
IN SW
V
OUT
D =
V
IN
I
is the maximum output current of the converter
OUT
-40
25
100
125
150
and f
is the oscillator switching frequency (127kHz).
SW
TEMPERATURE (°C)
For example, at V = 48V, V
= 3.3V, the ESR and
IN
OUT
input capacitance are calculated for the input peak-to-
peak ripple of 100mV or less, yielding an ESR and
capacitance value of 40mΩ and 100µF, respectively.
Figure 3. Forward-Voltage Drop vs. Temperature of the Internal
Body Diode of MAX5090
Low-ESR ceramic multilayer chip capacitors are recom-
mended for size-optimized application. For ceramic
capacitors assume the contribution from ESR and capaci-
tor discharge is equal to 10% and 90%, respectively.
Output Filter Capacitor
The output capacitor C
forms double pole with the
OUT
inductor and a zero with its ESR. The MAX5090’s inter-
nal fixed compensation is designed for a 100µF capaci-
tor, and the ESR must be from 20mΩ to 100mΩ. The
use of an aluminum or tantalum electrolytic capacitor is
recommended. See Table 2 to choose an output
capacitor for stable operation.
The input capacitor must handle the RMS ripple current
without significant rise in the temperature. The maxi-
mum capacitor RMS current occurs at approximately
50% duty cycle. Ensure that the ripple specification of
the input capacitor exceeds the worst-case capacitor
RMS ripple current. Use the following equations to cal-
culate the input capacitor RMS current:
The output ripple is comprised of ∆V
(caused by the
OQ
capacitor discharge), and ∆V
(caused by the ESR
OESR
of the capacitor). Use low-ESR tantalum or aluminum
electrolytic capacitors at the output. Use the following
equations to calculate the contribution of output capac-
itance and its ESR on the peak-to-peak output ripple
voltage:
2
2
I
= I
−I
AVGin
CRMS
PRMS
where:
D
3
2
2
I
=
(I
+ I
) x
PK DC
PRMS
PK
DC + I xI
∆V
= ∆I x ESR
V
I
OUT
OESR
L
OUT
V
x
I
=
AVGin
x η
∆I
IN
L
∆V
≈
OQ
∆I
8xC
x f
SW
L
2
OUT
I
= I
+
PK
OUT
The MAX5090 has a programmable soft-start time (t ).
SS
∆I
2
L
I
= I
−
DC
OUT
The output rise time is directly proportional to the out-
put capacitor, output voltage, and the load. The output
rise time also depends on the inductor value and the
current-limit threshold. It is important to keep the output
V
OUT
D =
V
IN
I
is the input switch RMS current, I
input average current, and η is the converter efficiency.
The ESR of the aluminum electrolytic capacitor increas-
es significantly at cold temperatures. Use a 1µF or
greater value ceramic capacitor in parallel with the alu-
minum electrolytic input capacitor, especially for input
voltages below 8V.
is the
PRMS
AVGin
rise time at startup the same as the soft-start time (t
)
SS
to avoid output overshoot. Large output capacitors take
longer than the programmed soft-start time (t ) and
SS
cause error-amplifier saturation. This results in output
overshoot. Use greater than 2ms soft-start time for a
100µF output capacitor.
12 ______________________________________________________________________________________
2A, 76V, High-Efficiency MAXPower Step-Down
DC-DC Converters
In a dynamic load application, the allowable deviation
of the output voltage during the fast transient load dic-
tates the output capacitance value and the ESR. The
output capacitors supply the step-load current until the
controller responds with a greater duty cycle. The
2) Minimize lead lengths to reduce stray capacitance,
trace resistance, and radiated noise. In particular,
place the Schottky rectifier diode right next to the
device. Also, place the BST and VD bypass capaci-
tors very close to the device.
response time (t
) depends on the closed-
RESPONSE
3) Connect the exposed pad of the IC to the SGND
plane. Do not make a direct connection between the
exposed pad plane and SGND (pin 7) under the IC.
Connect the exposed pad and pin 7 to the SGND
plane separately. Connect the ground connection of
the feedback resistive divider, ON/OFF threshold
resistive divider, and the soft-start capacitor to the
SGND plane. Connect the SGND plane and PGND
plane at one point near the input bypass capacitor
loop bandwidth of the converter. The resistive drop
across the capacitor ESR and capacitor discharge
cause a voltage droop during a step-load. Use a com-
bination of low-ESR tantalum and ceramic capacitors
for better transient load and ripple/noise performance.
Use the following equations to calculate the deviation of
output voltage due to the ESR and capacitance value
of the output capacitor:
at V .
IN
∆V
= I
x ESR
OESR
STEP OUT
4) Use large SGND plane as a heatsink for the
MAX5090. Use large PGND and LX planes as
heatsinks for the rectifier diode and the inductor.
I
x t
STEP
RESPONSE
∆V
=
OQ
C
OUT
where I
is the load step and t
is the
RESPONSE
STEP
response time of the controller. Controller response
time is approximately one-third of the reciprocal of the
closed-loop unity-gain bandwidth, 20kHz typically.
Board Layout Guidelines
1) Minimize ground noise by connecting the anode of
the Schottky rectifier, the input bypass capacitor
ground lead, and the output filter capacitor ground
lead to a large PGND plane.
______________________________________________________________________________________ 13
2A, 76V, High-Efficiency MAXPower Step-Down
DC-DC Converters
Application Circuit
V
IN
R
IN
C
IN
C
BYPASS
R1
R2
L1
V
OUT
V
DRAIN
IN
LX
ON/OFF
C
OUT
D1
C
BST
BST
FB
MAX5090B
SS
SYNC
SGND
C
SS
VD
PGND
3.3µF
Figure 4. Fixed Output Voltage
Table 2. Typical External Components Selection (Circuit of Figure 4)
V
(V)
V
(V)
I
(A)
EXTERNAL COMPONENTS
IN
OUT
OUT
MAX5090AATE
C
C
C
C
= 2 x 68µF/100V EEVFK2A680Q, Panasonic
IN
= 0.47µF/100V, GRM21BR72A474KA, Murata
BYPASS
= 220µF/6.3V 6SVP220MX, Sanyo
= 0.22µF/16V, GRM188R71C224K, Murata
OUT
BST
6.5 to 76
3.3
2
R1 = 0Ω
R2 = Open
R
IN
= 10Ω, 1% (0603)
D1 = PDS5100H, Diodes Inc.
L1 = 47µH, DO5022P-473
MAX5090BATE
C
C
C
C
= 2 x 68µF/100V EEVFK2A680Q, Panasonic
IN
= 0.47µF/100V, GRM21BR72A474KA, Murata
BYPASS
= 100µF/6.3V 6SVP100M, Sanyo
= 0.22µF/16V, GRM188R71C224K, Murata
OUT
BST
7.5 to 76
5
2
R1 = 0Ω
R2 = Open
R
IN
= 10Ω, 1% (0603)
D1 = PDS5100H, Diodes Inc.
L1 = 47µH, DO5022P-473
14 ______________________________________________________________________________________
2A, 76V, High-Efficiency MAXPower Step-Down
DC-DC Converters
Table 2. Typical External Components Selection (Circuit of Figure 4) (continued)
V
(V)
V
(V)
I
(A)
EXTERNAL COMPONENTS
= 330µF/50V EEVFK1H331Q, Panasonic
IN
OUT
OUT
MAX5090AATE
C
C
C
C
IN
= 0.47µF/50V, GRM21BR71H474KA, Murata
BYPASS
= 100µF/6.3V 6SVP100M, Sanyo
OUT
= 0.22µF/16V, GRM188R71C224K, Murata
BST
6.5 to 40
3.3
2
R1 = 0Ω
R2 = Open
R
IN
= 10Ω, 1% (0603)
D1 = B360, Diodes Inc.
L1 = 100µH, DO5022P-104
MAX5090BATE
C
C
C
C
= 330µF/50V EEVFK1H331Q, Panasonic
IN
= 0.47µF/50V, GRM21BR71H474KA, Murata
BYPASS
= 100µF/6.3V 6SVP100M, Sanyo
OUT
= 0.22µF/16V, GRM188R71C224K, Murata
BST
7.5 to 40
5
2
R1 = 0Ω
R2 = Open
R
IN
= 10Ω, 1% (0603)
D1 = B360, Diodes Inc.
L1 = 100µH, DO5022P-104
MAX5090CATE (V
programmed to 11V)
OUT
C
C
C
C
= 330µF/50V EEVFK1H331Q, Panasonic
IN
= 0.47µF/50V, GRM21BR71H474KA, Murata
BYPASS
= 100µF/16V 16SVP100M, Sanyo
= 0.22µF/16V, GRM188R71C224K, Murata
OUT
BST
R1 = 910kΩ
R2 = 100kΩ
15 to 40
11
2
R3 = 88.2kΩ, 1% (0603)
R4 = 10kΩ, 1% (0603)
R
IN
= 10Ω, 1% (0603)
D1 = B360, Diodes Inc.
L1 = 100µH, DO5022P-104
Table 3. Component Suppliers
SUPPLIER
WEBSITE
AVX
www.avxcorp.com
www.coilcraft.com
www.diodes.com
Coilcraft
Diodes Incorporated
Panasonic
Sanyo
www.panasonic.com
www.sanyo.com
TDK
www.component.tdk.com
www.vishay.com
Vishay
______________________________________________________________________________________ 15
2A, 76V, High-Efficiency MAXPower Step-Down
DC-DC Converters
V
IN
12V
R
IN
C
IN
68µF
C
BYPASS
V
OUT
100µH
5V, 2A
V
DRAIN
IN
LX
ON/OFF
D1
B360
C
OUT
C
BST
PTC
100µF
R
C
t
t
BST
FB
MAX5090B
SS
SYNC
SGND
C
SS
VD
PGND
3.3µF
*LOCATE PTC AS CLOSE TO HEAT-DISSIPATING COMPONENT AS POSSIBLE.
Figure 5. Load-Temperature Monitoring with ON/OFF (Requires Accurate V
)
IN
Chip Information
PROCESS: BCD
Ordering Information (continued)
OUTPUT
VOLTAGE
(V)
PIN-
PACKAGE*
TRANSISTOR COUNT: 7893
PART
TEMP RANGE
MAX5090CATE+ -40°C to +125°C 16 TQFN-EP**
Adj
Adj
MAX5090CATE -40°C to +125°C 16 TQFN-EP**
*The package code is T1655-3.
**EP = Exposed pad.
+Denotes lead-free package.
16 ______________________________________________________________________________________
2A, 76V, High-Efficiency MAXPower Step-Down
DC-DC Converters
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information
go to www.maxim-ic.com/packages.)
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 ____________________ 17
© 2006 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products, Inc.
Heslington
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