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PDF LTM4639 Data sheet ( Hoja de datos )
| Número de pieza | LTM4639 | |
| Descripción | 20A DC/DC uModule Step-Down Regulator | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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LTM4639
FEATURES
Low VIN 20A DC/DC
µModule Step-Down Regulator
DESCRIPTION
n Complete 20A Switch Mode Power Supply
n 2.375V to 7V Input Voltage Range (VIN < 4.5V,
Need CPWR Bias)
n 0.6V to 5.5V Output Voltage Range
n ±1.5% Maximum Total DC Output Voltage Error
(–40°C to 125°C)
n Differential Remote Sense Amplifier for Precision
Regulation (VOUT ≤ 3.3V)
n Current Mode Control/Fast Transient Response
n Parallel Multiphase Current Sharing (Up to 80A)
n Frequency Synchronization
n Selectable Pulse-Skipping or Burst Mode® Operation
n Soft-Start/Voltage Tracking
n Up to 88% Efficiency (3.3VIN, 1.5VOUT)
n Overcurrent Foldback Protection
n Output Overvoltage Protection
n Internal Temperature Monitor
n Overtemperature Protection
n 15mm × 15mm × 4.92mm BGA Package
APPLICATIONS
n Telecom Servers and Networking Equipment
n Industrial Equipment
n Medical Systems
n High Ambient Temperature Systems
n 3.3V Input Systems
The LTM®4639 is a complete 20A output high efficiency
switch mode step-down DC/DC µModule (micromodule)
regulator. Included in the package are the switching
controller, power FETs, inductor and compensation
components. Operating over an input voltage range from
2.375V to 7V, the LTM4639 supports an output voltage
range of 0.6V to 5.5V, set by a single external resistor.
Only a few input and output capacitors are needed.
Current mode operation allows precision current sharing of
up to four LTM4639 regulators to obtain up to 80A output.
High switching frequency and a current mode architecture
enable a very fast transient response to line and load
changes without sacrificing stability. The device supports
frequency synchronization, multiphase/current sharing,
Burst Mode operation and output voltage tracking for
supply rail sequencing. A diode-connected PNP transistor
is included for use as an internal temperature monitor. For
up to 20V input operation, please see the LTM4637.
The LTM4639 is offered in a 15mm × 15mm × 4.92mm
BGA package. The LTM4639 is RoHS compliant.
L, LT, LTC, LTM, PolyPhase, Burst Mode, µModule, Linear Technology, the Linear logo are
registered trademarks and LTpowerCAD is a trademark of Linear Technology Corporation.
All other trademarks are the property of their respective owners. Protected by U.S. Patents,
including 5481178, 5847554, 6580258, 6304066, 6476589, 6774611, 6677210, 8163643.
TYPICAL APPLICATION
3.3VIN, 1.5VOUT, 20A DC/DC µModule® Regulator
+5V BIAS
VIN
3.3V 22µF
6.3V
×4
CCOMPA
180pF
5k 0.1µF
100k
* SEE TABLE 5
** SEE TABLE 1
1µF 2.2µF
VIN CPWR EXTVCC INTVCC PGOOD
COMPA
VOUT
COMPB
TRACK/SS
RUN LTM4639
fSET
MODE_PLLIN
VOUT_LCL
DIFF_OUT
VOSNS+
VOSNS–
TEMP+
VFB
TEMP– SGND GND OT_TEST
CFF*
180pF
100µF*+
6.3V
×2
VOUT
1.5V
20A
680µF*
2.5V
×2
RFB**
40.2k
CBOT*
22pF
4639 TA01a
For more information www.linear.com/LTM4639
3.3V to 1.5V Efficiency
and Power Loss
100 4.5
95
EFFICIENCY
4.0
3.5
90 3.0
2.5
85
2.0
80
CPWR = 5V
FREQ = 400kHz
75
POWER LOSS
1.5
1.0
0.5
70 0
0 2 4 6 8 10 12 14 16 18 20
OUTPUT CURRENT (A)
4639 TA01b
4639f
1
1 page  
TYPICAL PERFORMANCE CHARACTERISTICS
LTM4639
2.5V Input Efficiency Graph
100
3.3V Efficiency Graph
100
5V Efficiency Graph
100
95 95 95
90 90 90
85
80
75
CPWR = 5V
FREQ = 350kHz
70
02 4 6 8
10 12
2.5V TO 1.8V
2.5V TO 1.5V
2.5V TO 1.2V
2.5V TO 1V
14 16 18 20
OUTPUT CURRENT (A)
4637 G01
7V Efficiency Graph
100
85
80
75
CPWR = 5V
FREQ = 400kHz
70
02 4 6 8
10 12
3.3V TO 2.5V
3.3V TO 1.8V
3.3V TO 1.5V
3.3V TO 1.2V
3.3V TO 1V
14 16 18 20
OUTPUT CURRENT (A)
4639 G02
2.5V to 1V with 7.5A/µs Load
Step, CPWR = 5V
85
80
75
70
0
CPWR = VIN
FREQ = 500kHz
5V TO 3.3V
5V TO 2.5V
5V TO 1.8V
5V TO 1.5V
5V TO 1.2V
5V TO 1V
2 4 6 8 10 12 14 16 18 20
OUTPUT CURRENT (A)
4639 G03
2.5V to 1.2V with 7.5A/µs Load
Step, CPWR = 5V
95
VOUT
VOUT
VP-P = 80mV
VP-P = 80mV
90
85
80
75
70
0
CPWR = VIN
FREQ = 550kHz
7V TO 5V
7V TO 3.3V
7V TO 2.5V
7V TO 1.8V
7V TO 1.5V
7V TO 1.2V
7V TO 1V
2 4 6 8 10 12 14 16 18 20
OUTPUT CURRENT (A)
4639 G03
LOAD
STEP
0A TO 7.5A
50µs/DIV
4639 G05
COMPA CONNECTED TO COMPB
CFF = 180pF, CBOT = 22pF, CCOMPA = 180pF
COUT = 100µF CER ×2,
680µF 2.5V 6mΩ POSCAP ×2
LOAD
STEP
0A TO 7.5A
50µs/DIV
4639 G06
COMPA CONNECTED TO COMPB
CFF = 180pF, CBOT = 22pF, CCOMPA = 180pF
COUT = 100µF CER ×2,
680µF 2.5V 6mΩ POSCAP ×2
2.5V to 1.5V with 7.5A/µs Load
Step, CPWR = 5V
3.3V to 1V with 7.5A/µs Load
Step, CPWR = 5V
3.3V to 1.2V with 7.5A/µs Load
Step, CPWR = 5V
VOUT
VP-P =
80mV
VOUT
VP-P = 80mV
VOUT
VP-P = 80mV
LOAD
STEP
0A TO
7.5A
LOAD
STEP
0A TO 7.5A
LOAD
STEP
0A TO 7.5A
50µs/DIV
4639 G07
COMPA CONNECTED TO COMPB
CFF = 180pF, CBOT = 22pF, CCOMPA = 180pF
COUT = 100µF CER ×2,
680µF 2.5V 6mΩ POSCAP ×2
50µs/DIV
4639 G08
COMPA CONNECTED TO COMPB
CFF = 180pF, CBOT = 22pF, CCOMPA = 180pF
COUT = 100µF CER ×2,
680µF 2.5V 6mΩ POSCAP ×2
50µs/DIV
4639 G09
COMPA CONNECTED TO COMPB
CFF = 180pF, CBOT = 22pF, CCOMPA = 180pF
COUT = 100µF CER ×2,
680µF 2.5V 6mΩ POSCAP ×2
For more information www.linear.com/LTM4639
4639f
5
5 Page 
LTM4639
APPLICATIONS INFORMATION
The typical LTM4639 application circuit is shown in Fig-
ure 22. External component selection is primarily
determined by the maximum load current and output
voltage. Refer to Table 5 for specific external capacitor
requirements for particular applications.
VIN to VOUT Step-Down Ratios
There are restrictions in the VIN to VOUT step-down ratio
that can be achieved for a given input voltage. The duty
cycle is 94% typical at 500kHz operation. The VIN to VOUT
minimum dropout is a function of load current and operation
at very low input voltage and high duty cycle applications.
At very low duty cycles the minimum 100ns on-time must
be maintained. See the Frequency Adjustment section and
temperature derating curves.
Output Voltage Programming
The PWM controller has an internal 0.6V ±1% reference
voltage. As shown in the Block Diagram, a 60.4k internal
feedback resistor connects the VOUT_LCL and VFB pins
together. When the remote sense amplifier is used, then
DIFF_OUT is connected to the VOUT_LCL pin. If the remote
sense amplifier is not used, then VOUT_LCL connects to
VOUT. The output voltage will default to 0.6V with no
feedback resistor. Adding a resistor RFB from VFB to ground
programs the output voltage:
VOUT
=
0.6V
•
60.4k +R
RFB
FB
Table 1. VFB Resistor Table vs Various Output Voltages
VOUT (V) 0.6 1.0 1.2 1.5 1.8 2.5 3.3
RFB (k) Open 90.9 60.4 40.2 30.1 19.1 13.3
5.0
8.25
For parallel operation of N LTM4639s, the following
equation can be used to solve for RFB:
RFB=
60.4k
VOUT
0.6V
/N
–1
Tie the VFB pins together for each parallel output. The
COMP pins must be tied together also.
Input Capacitors
The LTM4639 module should be connected to a low AC-
impedance DC source. Additional input capacitors are
needed fortheRMSinput ripple current rating.The ICIN(RMS)
equation which follows can be used to calculate the input
capacitor requirement. Typically 22µF X7R ceramics are a
good choice with RMS ripple current ratings of ~ 2A each.
A 47µF to 100µF surface mount aluminum electrolytic bulk
capacitor can be used for more input bulk capacitance.
This bulk input capacitor is only needed if the input source
impedance is compromised by long inductive leads, traces
or not enough source capacitance. If low impedance power
planes are used, then this bulk capacitor is not needed.
For a buck converter, the switching duty cycle can be
estimated as:
D=
VOUT
VIN
Without considering the inductor ripple current, for each
output the RMS current of the input capacitor can be
estimated as:
ICIN(RMS)=
IOUT(MAX )
η%
•
D • (1– D)
where η% is the estimated efficiency of the power module.
The bulk capacitor can be a switcher-rated aluminum
electrolytic capacitor or a Polymer capacitor.
Output Capacitors
The LTM4639 is designed for low output voltage ripple
noise. The bulk output capacitors defined as COUT are
chosen with low enough effective series resistance
(ESR) to meet the output voltage ripple and transient
requirements. COUT can be a low ESR tantalum capacitor,
low ESR Polymer capacitor or ceramic capacitors. The
typical output capacitance range is from 200µF to 800µF.
Additional output filtering may be required by the system
designer if further reduction of output ripple or dynamic
transient spikes is required. Table 5 shows a matrix
of different output voltages and output capacitors to
minimize the voltage droop and overshoot during a 10A/µs
transient. The table optimizes total equivalent ESR and total
bulk capacitance to optimize the transient performance.
For more information www.linear.com/LTM4639
4639f
11
11 Page | ||
| Páginas | Total 30 Páginas | |
| PDF Descargar | [ Datasheet LTM4639.PDF ] | |
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