LTM8029_1208 [Linear]
36VIN 600mA Step-Down μModule Converter with 5μA Quiescent Current; 36VIN 600mA降压转换器μModule与5μA静态电流
| 型号： | LTM8029_1208 |
| 厂家： | 
Linear |
| 描述： | 36VIN 600mA Step-Down μModule Converter with 5μA Quiescent Current |
| 文件： | 总20页 (文件大小：259K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LTM8029
36V , 600mA Step-Down
IN
µModule Converter with
5µA Quiescent Current
DescripTion
FeaTures
The LTM®8029 is a 36V , 600mA step-down µModule®
n
Complete Switch Mode Power Supply
IN
Low Quiescent Current Burst Mode® Operation
converter with 5µA quiescent current. It is an adjustable
frequency buck switching regulator that consumes only
5μA of quiescent current. The LTM8029 can accept an
n
5μA I at 12V to 3.3V
Q
IN
OUT
n
n
n
n
n
n
n
n
n
600mA Output Current
Wide Input Voltage Range: 4.5V to 36V (40V
Output Voltage: 1.2V to 18V
Excellent Dropout Performance
Can Be Used As an Inverter
Adjustable Switching Frequency: 200kHz to 2.2MHz
Current Mode Control
(e1) RoHS Compliant Package
Tiny, Low Profile (11.25mm × 6.25mm × 3.42mm)
Surface Mount BGA Package
)
input as high as 36V and operates at low input voltages
MAX
IN
due to its off-time skipping capability. Burst Mode opera-
tion maintains high efficiency at low output currents while
keeping the output ripple low. The RUN pin features an
accurate threshold and the shutdown current is 0.9μA.
A power good flag signals when V
programmed output voltage.
reaches 90% of the
OUT
The LTM8029 is packaged in a thermally enhanced,
compact (11.25mm × 6.25mm) and low profile (3.42mm)
overmolded ball grid array (BGA) package suitable for
automated assembly by standard surface mount equip-
ment. The LTM8029 is RoHS compliant.
applicaTions
n
Automotive Battery Regulation
L, LT, LTC, LTM, Linear Technology, the Linear logo, Burst Mode and µModule are registered
trademarks of Linear Technology Corporation. All other trademarks are the property of their
respective owners.
n
Power for Portable Products
n
Distributed Supply Regulation
n
Industrial Supplies
n
Wall Transformer Regulation
Typical applicaTion
Low Quiescent Current, 5VOUT, 600mA µModule Regulator
Minimum Input Voltage vs Output Current
5.8
LTM8029
V
V
IN
OUT
V
V
OUT
IN
5.6V TO 36V
5V
5.7
5.6
5.5
5.4
600mA
RUN
BIAS
1µF
22µF
PGOOD
RT
GND
158k
FB
309k
f = 800kHz
8029 TA01a
400
OUTPUT CURRENT (mA)
600
0
100
200
300
500
8029 TA01b
8029fa
1
LTM8029
absoluTe MaxiMuM raTings
pin conFiguraTion
(Notes 1, 2)
TOP VIEW
V , RUN ..................................................................40V
OUT
IN
V
IN
5
V
, BIAS ................................................................20V
BANK 1
VOUT
V + BIAS.................................................................55V
4
3
2
1
IN
BANK 3
PGOOD , FB, RT..........................................................6V
Maximum Internal Temperature ........................... 125°C
Solder Temperature...............................................260°C
BIAS
FB PGOOD
RUN RT
GND
BANK 2
A
B
C
D
E
F
G
H
BGA PACKAGE
35-LEAD (11.25mm × 6.25mm × 3.42mm)
T
JMAX
= 125°C, θ = 13.8°C/W, θ
= 17.2°C/W,
JA
JCtop
θ
= 3.9°C/W, θ = 9.0°C/W
JCbottom
JCB
WEIGHT = 0.6g
orDer inForMaTion
LEAD FREE FINISH
LTM8029EY#PBF
LTM8029IY#PBF
LTM8029MPY#PBF
TRAY
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
–40°C to 125°C
LTM8029EY#PBF
LTM8029IY#PBF
LTM8029Y
35-Lead (11.25mm × 6.25mm × 3.42mm) BGA
35-Lead (11.25mm × 6.25mm × 3.42mm) BGA
35-Lead (11.25mm × 6.25mm × 3.42mm) BGA
LTM8029Y
–40°C to 125°C
LTM8029MPY#PBF LTM8029Y
–55°C to 125°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
This product is only offered in trays. For more information go to: http://www.linear.com/packaging/
8029fa
2
LTM8029
elecTrical characTerisTics The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 12V, RUN = 2V unless otherwise noted (Note 2).
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
l
Minimum Input Voltage
Output DC Voltage
4.5
V
I
I
≤ 0.6A, R Open
1.2
3.3
V
V
OUT
OUT
FB
≤ 0.6A, R = 576k
FB
Output DC Current
3.3V
10
600
9
mA
OUT
Quiescent Current Into V
RUN = 0V
No Load
No Load
0.9
5
µA
µA
µA
IN
l
BIAS Current
600mA Load
IN
3.6
4.7
mA
mA
V
= 32V, V
= 20V at 100mA Load
OUT
Line Regulation
Load Regulation
5.5V < V < 36V, I
= 600mA
OUT
0.3
0.4
10
%
%
IN
10mA < I
< 600mA
OUT
Output RMS Voltage Ripple
Switching Frequency
I
= 600mA
mV
OUT
R = 41.2k
2.2
1
200
MHz
MHz
kHz
T
R = 124k
T
R = 768k
T
Voltage at FB Pin
1.185
1.175
1.20
1.20
1.215
1.225
V
V
l
l
l
Internal Feedback Resistor
Minimum BIAS Voltage for Proper Operation
RUN Pin Current
1
1.7
1
MΩ
V
2.25
30
RUN = 2.5V
nA
V
RUN Threshold Voltage
0.95
1.3
RUN Voltage Hysteresis
PGOOD Threshold (at FB)
PGOOD Leakage Current
PGOOD Sink Current
30
1.1
0.1
100
mV
V
V
Rising
OUT
PGOOD = 6V
1
µA
µA
PGOOD = 0.4V
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: The LTM8029E is guaranteed to meet performance specifications
from 0°C to 125°C internal. Specifications over the full –40°C to
125°C internal operating temperature range are assured by design,
characterization and correlation with statistical process controls.
The LTM8029I is guaranteed to meet specifications over the full –40°C
to 125°C internal operating temperature range. The LTM8029MP is
guaranteed to meet specifications over the full –55°C to 125°C internal
operating temperature range. Note that the maximum internal temperature
is determined by specific operating conditions in conjunction with board
layout, the rated package thermal resistance and other environmental
factors.
8029fa
3
LTM8029
Typical perForMance characTerisTics
TA = 25°C, unless otherwise noted. Configured per Table 1, where applicable.
2.5VOUT Efficiency vs Output
Current, BIAS = 5V
3.3VOUT Efficiency vs Output
Current, BIAS = 5V
5VOUT Efficiency vs Output
Current, BIAS = 5V
90
85
80
75
70
65
60
55
50
90
85
80
75
70
65
60
55
50
90
85
80
75
70
65
60
5V
5V
IN
IN
12V
24V
36V
12V
24V
36V
12V
24V
36V
IN
IN
IN
IN
IN
IN
IN
IN
IN
0
100
200
300
400
500
600
0
100
200
300
400
500
600
0
100
200
300
400
500
600
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
8029 G01
8029 G02
8029 G03
8VOUT Efficiency vs Output
Current, BIAS = 5V
12VOUT Efficiency vs Output
Current, BIAS = 5V
18VOUT Efficiency vs Output
Current, BIAS = 5V
95
90
85
80
75
70
100
95
90
85
80
75
70
100
98
96
94
92
90
88
86
84
82
80
12V
24V
36V
IN
IN
IN
24V
36V
24V
36V
IN
IN
IN
IN
0
100
200
300
400
500
600
0
100
200
300
400
500
600
0
100
200
300
400
500
600
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
8029 G04
8029 G05
8029 G06
Input Current vs Output Current,
2.5VOUT, BIAS = 5V
Input Current vs Output Current,
3.3VOUT, BIAS = 5V
Input Current vs Output Current,
5VOUT, BIAS = 5V
450
400
350
300
250
200
150
100
50
350
300
250
200
150
100
50
600
500
400
300
200
100
0
5V
IN
12V
IN
5V
IN
12V
IN
24V
IN
12V
IN
24V
IN
36V
IN
24V
IN
36V
IN
36V
IN
0
0
0
100
200
300
400
500
600
100
200
300
400
500
600
0
100
200
OUTPUT CURRENT (mA)
300
400
500
600
0
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
8029 G07
8029 G09
8029 G08
8029fa
4
LTM8029
Typical perForMance characTerisTics
TA = 25°C, unless otherwise noted. Configured per Table 1, where applicable.
Input Current vs Output Current,
8VOUT, BIAS = 5V
Input Current vs Output Current,
12VOUT, BIAS = 5V
Input Current vs Output Current,
18VOUT, BIAS = 5V
500
450
400
350
300
250
200
150
100
50
400
350
300
250
200
150
100
50
500
450
400
350
300
250
200
150
100
50
12V
24V
36V
24V
36V
24V
36V
IN
IN
IN
IN
IN
IN
IN
0
0
0
0
100
200
300
400
500
600
0
100
200
300
400
500
600
0
100
200
300
400
500
600
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
8029 G10
8029 G11
8029 G12
Minimum VIN vs VOUT
,
Input Current vs VIN,
Output Short, BIAS = 5V
Output Short-Circuit Current,
BIAS = 5V
IOUT = 600mA, BIAS = 5V
25
20
15
10
5
1700
1600
1500
1400
1300
1200
1100
1000
450
400
350
300
250
200
150
100
50
f = 800kHz
f = 800kHz
f = 400kHz
f = 400kHz
0
0
0
5
10
15
20
0
10
20
(V)
30
40
0
10
20
(V)
30
40
V
(V)
V
V
OUT
IN
IN
8029 G13
8029 G15
8029 G14
IBIAS vs Output Current,
3.3VOUT, BIAS = 5V
IBIAS vs Output Current,
5VOUT, BIAS = 5V
IBIAS vs IOUT, 2.5VOUT, BIAS = 5V
8
7
6
5
4
3
2
1
0
8
7
6
5
4
3
2
1
0
10
9
8
7
6
5
4
3
2
1
0
5V
IN
12V
IN
5V
IN
12V
IN
24V
IN
12V
IN
24V
IN
36V
IN
24V
IN
36V
IN
36V
IN
0
100
200
300
(mA)
400
500
600
0
100
200
300
400
500
600
0
100
200
300
400
500
600
I
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
OUT
8029 G16
8029 G18
8029 G17
8029fa
5
LTM8029
Typical perForMance characTerisTics
TA = 25°C, unless otherwise noted. Configured per Table 1, where applicable.
IBIAS vs Output Current,
8VOUT, BIAS = 5V
IBIAS vs Output Current,
12VOUT, BIAS = 5V
IBIAS vs Output Current,
18VOUT, BIAS = 5V
10
9
8
7
6
5
4
3
2
1
0
8
7
6
5
4
3
2
1
0
12
10
8
12V
24V
36V
24V
36V
24V
36V
IN
IN
IN
IN
IN
IN
IN
6
4
2
0
0
100
200
300
400
500
600
0
100
200
300
400
500
600
0
100
200
300
400
500
600
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
8029 G19
8029 G20
8029 G21
Minimum VIN vs Output Current,
–3.3VOUT, BIAS = GND
Minimum VIN vs Output Current,
–5VOUT, BIAS = GND
Minimum VIN vs Output Current,
–8VOUT, BIAS = GND
8
7
6
5
4
3
2
1
0
12
10
8
20
18
16
14
12
10
8
TO START
6
TO START
RUNNING
4
RUNNING
6
TO START
RUNNING
4
2
2
0
0
0
100 200 300 400 500 600 700
OUTPUT CURRENT (mA)
8029 G22
0
100
200
300
400
500
600
0
100
200
300
400
500
600
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
8029 G23
8029 G24
Minimum VIN vs Output Current,
–12VOUT, BIAS = GND
Minimum VIN vs Output Current,
–18VOUT, BIAS = GND
Temperature Rise vs Output
Current, 2.5VOUT
25
20
15
10
5
20
18
16
14
12
10
8
18
16
14
12
10
8
12V
IN
TO START
RUNNING
24V
36V
IN
IN
6
6
TO START
RUNNING
4
4
2
2
0
0
0
0
100
200
300
400
500
0
50 100 150 200 250 300 350
OUTPUT CURRENT (mA)
8029 G26
0
100
200
300
400
500
600
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
8029 G25
8029 G27
8029fa
6
LTM8029
Typical perForMance characTerisTics
TA = 25°C, unless otherwise noted. Configured per Table 1, where applicable.
Temperature Rise vs Output
Current, 3.3VOUT
Temperature Rise vs Output
Current, 5VOUT
Temperature Rise vs Output
Current, 8VOUT
25
20
15
10
5
25
20
15
10
5
18
16
14
12
10
8
12V
IN
12V
IN
12V
IN
24V
IN
24V
IN
24V
IN
36V
IN
36V
IN
36V
IN
6
4
2
0
0
0
0
100
200
300
400
500
600
0
100
200
300
400
500
600
0
100
200
300
400
500
600
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
8029 G29
8029 G30
8029 G28
Temperature Rise vs Output
Current, 12VOUT
Temperature Rise vs Output
Current, 18VOUT
Temperature Rise vs Output
Current, –3.3VOUT
25
20
15
10
5
30
25
20
15
10
5
25
20
15
10
5
24V
36V
24V
36V
12V
24V
IN
IN
IN
IN
IN
IN
0
0
0
0
100
200
300
400
500
600
0
100
200
300
400
500
600
0
100
200
300
400
500
600
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
8029 G31
8029 G32
8029 G33
Temperature Rise vs Output
Current, –5VOUT
Temperature Rise vs Output
Current, –8VOUT
Temperature Rise vs Output
Current, –12VOUT
30
25
20
15
10
5
35
30
25
20
15
10
5
35
30
25
20
15
10
5
12V
24V
12V
24V
12V
24V
IN
IN
IN
IN
IN
IN
0
0
0
0
100
200
300
400
500
600
0
100
200
300
400
500
600
0
100
200
300
400
500
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
8029 G34
8029 G35
8029 G36
8029fa
7
LTM8029
pin FuncTions
V (Bank1):TheV pinssupplycurrenttotheLTM8029’s
FB (Pin A2): The LTM8029 regulates its FB pin to 1.2V.
IN
IN
internal regulator and to the internal power switch. This
pin must be locally bypassed with an external, low ESR
capacitor; see Table 1 for recommended values.
Connect the output feedback resistor from this pin to
ground. The value of R is given by the equation R
=
FB
FB
1200/(V
– 1.2), where R is in kΩ.
OUT
FB
V
(Bank 3): Power Output Pins. Apply the output filter
RT (Pin B1): The RT pin is used to program the switching
frequency of the LTM8029 by connecting a resistor from
thispintoground.TheApplicationsInformationsectionof
the data sheet includes a table to determine the resistance
value based on the desired switching frequency.
OUT
capacitor and the output load between these pins and
GND pins.
GND (Bank 2): Tie these GND pins to a local ground plane
below the LTM8029 and the circuit components. In most
applications the bulk of the heat flow out of the LTM8029
is through these pads, so the printed circuit design has a
large impact on the thermal performance of the part. See
the PCB Layout and Thermal Considerations sections for
PGOOD (Pin B2): The PGOOD pin is the open-collector
output of an internal comparator that monitors the FB pin.
PGOOD remains low until the FB pin is within 10% of the
final regulation voltage. PGOOD output is valid when V
IN
moredetails.Returnthefeedbackresistor(R )tothisnet.
is above 4.5V and RUN is high. If this function is not used,
FB
leave this pin floating.
RUN (Pin A1): Pull the RUN pin below 0.95V to shut down
the LTM8029. Tie to 1.3V or more for normal operation.
BIAS (Pin H3): The BIAS pin powers internal circuitry.
Connect to a power source greater than 2.25V and less
than 20V. If the output is greater than 2.25V, connect this
If the shutdown feature is not used, tie this pin to V .
IN
pin there. Also, make sure that BIAS + V is less than 55V.
IN
block DiagraM
22µH
V
V
IN
OUT
1M
1%
0.1µF
47pF
1µF
BIAS
CURRENT
MODE
CONTROLLER
RUN
GND
RT
PGOOD
FB
8029 BD
8029fa
8
LTM8029
operaTion
The LTM8029 is a standalone non-isolated step-down
switchingDC/DCpowersupplythatcandeliverupto600mA
ofoutputcurrent.Thisdevicefeaturesaverylowquiescent
current and provides a precisely regulated output voltage
from 1.2V to 18V. The input voltage range is 4.5V to 36V.
Given that the LTM8029 is a step-down converter, make
sure that the input voltage is high enough to support the
desired output voltage and load current.
typically 5μA at no load and 12V . Since the LTM8029 is
IN
mostly shut down between bursts, the effective switching
frequency will be lower than that programmed at the RT
pin. For the same reason, the output ripple will be differ-
ent than when the part is running at the full programmed
frequency.
The LTM8029 contains a power good comparator which
trips when the FB pin is at roughly 90% of its regulated
value. The PGOOD output is an open-collector transistor
that is off when the output is in regulation, allowing an
external resistor to pull the PGOOD pin high. Power good
As shown in the Block Diagram, the LTM8029 contains a
current mode controller, power switching element, power
inductor, power Schottky diode and a modest amount of
input and output capacitance. The LTM8029 is a fixed
frequency PWM regulator. The switching frequency is set
by simply connecting the appropriate resistor value from
the RT pin to GND. An internal regulator provides power
to the control circuitry.
is valid when the LTM8029 is enabled and V is above
IN
4.5V. The LTM8029 features the ability to skip the off-time
in switching cycles when the input voltage approaches the
target output. This allows the LTM8029 to operate at input
voltages lower than other step-down regulators.
The internal regulator normally draws power from the V
In an overload or short-circuit condition, the LTM8029
will protect itself by limiting its peak switching current
and decreasing the operating frequency to reduce overall
power consumption. The LTM8029 is also equipped with
a thermal shutdown that will inhibit power switching at
highjunctiontemperatures.Theactivationthresholdofthis
function,however,isabove125°Ctoavoidinterferingwith
normal operation. Thus, prolonged or repetitive operation
underaconditioninwhichthethermalshutdownactivates
may damage or impair the reliability of the device.
IN
pin, but if the BIAS pin is connected to an external volt-
age higher than 2.25V, bias power will be drawn from the
external source (typically the regulated output voltage).
This improves efficiency.
The RUN pin is used to place the LTM8029 in shutdown.
To optimizeefficiency,theLTM8029automaticallyswitches
to Burst Mode operation in light load situations. Between
bursts, all circuitry associated with controlling the output
switch is shut down reducing the input supply current to
8029fa
9
LTM8029
applicaTions inForMaTion
For most applications, the design process is straight
forward, summarized as follows:
Capacitor Selection Considerations
The C and C capacitor values in Table 1 are the
IN
OUT
1. Look at Table 1 and find the row that has the desired
input range and output voltage.
minimum recommended values for the associated oper-
ating conditions. Applying capacitor values below those
indicated in Table 1 is not recommended, and may result
in undesirable operation. Using larger values is generally
acceptable, and can yield improved dynamic response,
if it is necessary. It is incumbent upon the user to verify
properoperation overthe intended system’sline, loadand
environmental conditions.
2. Apply the recommended C , C , R and R values.
IN OUT FB
T
3. Connect BIAS as indicated.
While these component combinations have been tested
for proper operation, it is incumbent upon the user to
verify proper operation over the intended system’s line,
load and environmental conditions. Bear in mind that the
maximum output current is limited by junction tempera-
ture, therelationshipbetweentheinputandoutputvoltage
magnitude and polarity and other factors. Please refer to
the graphs in the Typical Performance Characteristics
section for guidance.
Ceramic capacitors are small, robust and have very low
ESR. However, not all ceramic capacitors are suitable.
X5R and X7R types are stable over temperature and ap-
plied voltage and give dependable service. Other types,
including Y5V and Z5U have very large temperature and
voltage coefficients of capacitance. In an application cir-
cuit they may have only a small fraction of their nominal
capacitance resulting in much higher output voltage ripple
than expected.
Themaximumfrequency(andattendantR value)atwhich
T
the LTM8029 should be allowed to switch is given in
Table 1 in the f
column, while the recommended fre-
MAX
quency(andR value)foroptimalefficiencyoverthegiven
Ceramic capacitors are also piezoelectric. In Burst Mode
operation, the LTM8029’s switching frequency depends
on the load current, and can excite a ceramic capacitor
at audio frequencies, generating audible noise. Since the
LTM8029 operates at a lower current limit during Burst
Mode operation, the noise is typically very quiet to a ca-
sual ear. If this audible noise is unacceptable, use a high
performance electrolytic capacitor at the output. It may
also be a parallel combination of a ceramic capacitor and
a low cost electrolytic capacitor.
T
input condition is given in the f
column.
OPTIMAL
TheLTM8029iscapableofoperatingatlowinputvoltages
by skipping off-times to maintain regulation. This results
in a lower operating frequency than that programmed by
the RT pin, so it may be necessary to use larger input and
output capacitors, depending upon the system require-
ments. The recommended components and V range
IN
listed in Table 1 reflect an operation where off-times are
not skipped.
A final precaution regarding ceramic capacitors concerns
the maximum input voltage rating of the LTM8029. A
ceramic input capacitor combined with trace or cable
inductance forms a high Q (under damped) tank circuit.
If the LTM8029 circuit is plugged into a live supply, the
input voltage can ring to twice its nominal value, possi-
bly exceeding the device’s rating. This situation is easily
avoided; see the Hot-Plugging Safety section.
8029fa
10
LTM8029
applicaTions inForMaTion
Table 1. Recommended Component Values and Configuration
V
IN
(V)*
V
OUT
(V)
C
C
BIAS
R
FB
f
R
T(OPT)
f
R
T(MIN)
IN
OUT
OPT
MAX
4.5-36
4.5-36
4.5-36
4.5-36
4.5-36
4.5-36
4.8-36
7.8-36
12-36
17-36
24.5-36
10-33
5.5-33
8-31
1.2
4.7µF 50V 1206 X5R
4.7µF 50V 1206 X5R
4.7µF 50V 1206 X5R
4.7µF 50V 1206 X5R
1µF 50V 1206 X5R
1µF 50V 0805 X5R
1µF 50V 0805 X5R
1µF 50V 0805 X5R
2.2µF 50V 1206 X5R
2.2µF 50V 1206 X5R
2.2µF 50V 1206 X5R
1µF 50V 0805 X5R
4.7µF 50V 1206 X5R
2.2µF 50V 1206 X5R
2.2µF 50V 1206 X5R
2.2µF 50V 1206 X5R
100µF 6.3V 1206 X5R 2.1V-20V Open
100µF 6.3V 1206 X5R 2.1V-20V 4.02M
270kHz
310kHz
350kHz
380kHz
450kHz
490kHz
615kHz
800kHz
830kHz
880kHz
880kHz
615kHz
615kHz
800kHz
830kHz
880kHz
536k
475k
402k
374k
309k
280k
215k
158k
150k
137k
137k
215k
215k
158k
150k
137k
510kHz
600kHz
750kHz
780kHz
840kHz
950kHz
1.2MHz
1.6MHz
2.2MHz
2.2MHz
2.2MHz
1.2MHz
1.2MHz
1.6MHz
2.2MHz
2.2MHz
267k
220k
169k
162k
147k
127k
93.1k
61.9k
41.2k
41.2k
41.2k
93.1k
93.1k
61.9k
41.2k
41.2k
1.5
1.8
2
100µF 6.3V 1206 X5R 2.1V-20V
100µF 6.3V 1206 X5R 2.1V-20V
2M
1.5M
2.2
2.5
3.3
5
47µF 6.3V 1206 X5R
47µF 6.3V 1206 X5R
22µF 6.3V 1206 X5R
22µF 6.3V 1206 X5R
22µF 10V 1210 X5R
10µF 50V 1210 X5R
10µF 50V 1210 X5R
22µF 6.3V 1206 X5R
100µF 6.3V 1206 X5R
47µF 6.3V 1206 X5R
22µF 10V 1210 X5R
22µF 16V 1210 X5R
2.1V-20V 1.21M
2.1V-20V
931k
576k
309k
174k
110k
V
V
OUT
OUT
8
2.1V-20V
2.1V-20V
12
18
2.1V-20V 71.5k
–3.3
–3.3
–5
GND
GND
GND
GND
GND
576k
576k
309k
174k
110k
7-28
–8
7-24
–12
4.5-24
4.5-24
4.5-24
4.5-24
4.5-24
4.5-24
1.8-24
7.8-24
12-24
17-24
1.2
1.5
1.8
2
2.2µF 50V 0805 X7R
2.2µF 50V 0805 X7R
2.2µF 50V 0805 X7R
2.2µF 50V 0805 X7R
1µF 50V 0805 X5R
1µF 50V 0805 X5R
1µF 25V 0603 X5R
1µF 25V 0603 X5R
2.2µF 50V 1206 X5R
2.2µF 50V 1206 X5R
47µF 6.3V 1206 X5R
47µF 6.3V 1206 X5R
47µF 6.3V 1206 X5R
47µF 6.3V 1206 X5R
47µF 6.3V 1206 X5R
47µF 6.3V 1206 X5R
22µF 6.3V 1206 X5R
22µF 6.3V 1206 X5R
22µF 10V 1210 X5R
10µF 50V 1210 X5R
2.1V-20V Open
2.1V-20V 4.02M
400kHz
430kHz
450kHz
480kHz
545kHz
580kHz
615kHz
800kHz
830kHz
880kHz
348k
324k
309k
287k
249k
232k
215k
158k
150k
137k
750kHz
930kHz
1MHz
169k
130k
124k
93.1k
82.5k
73.2k
41.2k
41.2k
41.2k
41.2k
2.1V-20V
2.1V-20V
2M
1.5M
1.2MHz
1.3MHz
1.4MHz
2.2MHz
2.2MHz
2.2MHz
2.2MHz
2.2
2.5
3.3
5
2.1V-20V 1.21M
2.1V-20V
931k
576k
309k
174k
110k
V
V
OUT
OUT
8
2.1V-20V
2.1V-20V
12
9-15
9-15
9-15
9-15
9-15
9-15
9-15
9-15
12-15
1.2
1.5
1.8
2
2.2µF 50V 0805 X7R
2.2µF 50V 0805 X7R
2.2µF 50V 0805 X7R
2.2µF 50V 0805 X7R
1µF 50V 0805 X5R
1µF 50V 0805 X5R
1µF 25V 0603 X5R
1µF 25V 0603 X5R
2.2µF 50V 1206 X5R
47µF 6.3V 1206 X5R
47µF 6.3V 1206 X5R
47µF 6.3V 1206 X5R
47µF 6.3V 1206 X5R
47µF 6.3V 1206 X5R
47µF 6.3V 1206 X5R
22µF 6.3V 1206 X5R
22µF 6.3V 1206 X5R
22µF 10V 1210 X5R
2.1V-20V Open
2.1V-20V 4.02M
400kHz
430kHz
450kHz
480kHz
545kHz
580kHz
615kHz
800kHz
830kHz
348k
324k
309k
287k
249k
232k
215k
158k
150k
1.3MHz
1.5MHz
1.7MHz
1.9MHz
2MHz
84.5k
66.5k
57.6k
49.9k
46.4k
41.2k
41.2k
41.2k
41.2k
2.1V-20V
2.1V-20V
2M
1.5M
2.2
2.5
3.3
5
2.1V-20V 1.21M
2.1V-20V
931k
576k
309k
174k
2.2MHz
2.2MHz
2.2MHz
2.2MHz
V
V
OUT
OUT
8
2.1V-20V
Notes: An input bulk capacitor is required. Do not allow V + BIAS to exceed 55V. The minimum input operating voltage may be lower than given in the table.
IN
Refer to the Applications Information section for details.
8029fa
11
LTM8029
applicaTions inForMaTion
Frequency Selection
BIAS Pin Considerations
The LTM8029 uses a constant frequency PWM architec-
ture that can be programmed to switch from 200kHz to
2.2MHz by using a resistor tied from the RT pin to ground.
The BIAS pin is used to provide drive power for the in-
ternal power switching stage and operate other internal
circuitry. For proper operation, it must be powered by at
least 2.25V. If the output voltage is programmed to 2.25V
Table 2 provides a list of R resistor values and their
T
resultant frequencies.
or higher, BIAS may be simply tied to V . If V
is less
OUT
OUT
than 2.25V, BIAS can be tied to V or some other voltage
IN
Table 2. Frequency vs RT Value
source. If the BIAS pin voltage is too high, the efficiency
of the LTM8029 may suffer. The optimum BIAS voltage is
dependent upon many factors, such as load current, input
voltage, outputvoltageandswitchingfrequency, but4Vto
5V works well in many applications. In all cases, ensure
that the maximum voltage at the BIAS pin is less than 25V
FREQUENCY (MHz)
R (k)
T
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
2.2
768
348
220
158
124
93.1
73.2
61.9
52.3
46.4
41.2
and that the sum of V and BIAS is less than 55V. If BIAS
IN
power is applied from a remote or noisy voltage source, it
may be necessary to apply a decoupling capacitor locally
to the pin.
Burst Mode Operation
To enhance efficiency at light loads, the LTM8029 auto-
matically switches to Burst Mode operation which keeps
the output capacitor charged to the proper voltage while
minimizing the input quiescent current. During Burst
Modeoperation, theLTM8029deliverssinglecyclebursts
of current to the output capacitor followed by sleep pe-
riods where the output power is delivered to the load by
the output capacitor. Since the LTM8029 is mostly shut
down between bursts, the effective switching frequency
will be lower than that programmed at the RT pin. For the
same reason, the output ripple will be different than when
the part is running at the full programmed frequency.
Operating Frequency Trade-offs
It is recommended that the user apply the optimal R
T
resistor value given in Table 1 for the input and output
operatingcondition. Systemlevelorotherconsiderations,
however, may necessitate another operating frequency.
While the LTM8029 is flexible enough to accommodate
a wide range of operating frequencies, a haphazardly
chosen one may result in undesirable operation under
certain operating or fault conditions. A frequency that is
too high can reduce efficiency, generate excessive heat
or even damage the LTM8029 if the output is overloaded
or short-circuited. A frequency that is too low can result
in a final design that has too much output ripple or too
large of an output capacitor. In addition, as shown in the
Typical Performance Characteristics section, the operat-
ing frequency affects the amount of current that may be
delivered during a short-circuit condition.
In addition, V and BIAS quiescent currents are each
IN
greatly reduced during the sleep time. As the load current
decreases towards a no load condition, the percentage of
time that the LTM8029 operates in sleep mode increases
and the average input current is greatly reduced, resulting
in higher efficiency.
8029fa
12
LTM8029
applicaTions inForMaTion
RUN
Italsomeansthattheeffectivefrequencyduringthismode
ofoperation willbelowerthan the one programmedby the
resistor connected to the RT pin, so it may be necessary
to use larger input and output capacitors, depending upon
the system requirements.
The LTM8029 is in shutdown when the RUN pin is low
and active when the pin is high. The rising threshold of the
RUNcomparatoristypically1.15V,witha30mVhysteresis.
This threshold is accurate when V is above 4.5V. Adding
IN
a resistor divider from V to RUN programs the LTM8029
IN
Shorted Input Protection
to operate only when V is above a desired voltage (see
IN
Care needs to be taken in systems where the output will be
held high when the input to the LTM8029 is absent. This
may occur in battery charging applications or in battery
backup systems where a battery or some other supply is
Figure 1). This rising threshold voltage, V
, can be
IN(RUN)
adjusted by setting the values R3 and R4 such that they
satisfy the following equation:
R3+ R4
diode ORed with the LTM8029’s output. If the V pin is
VIN(RUN)
=
• 1.15V
IN
R4
allowed to float and the RUN pin is held high (either by a
logicsignalorbecauseitistiedtoV ),thentheLTM8029’s
IN
where the LTM8029 should not start until V is above
IN
internal circuitry will pull its quiescent current through
its internal power switch. This is fine if your system can
tolerate a few milliamps in this state. If you ground the
RUN pin, the input current will drop to essentially zero.
V
. NotethatduetotheRUNpin’shysteresis, opera-
tionwillnotstopuntiltheinputfallsslightlybelowV
IN(RUN)
.
IN(RUN)
LTM8029
However, if the V pin is grounded while the output is
IN
V
V
IN
IN
held high, then parasitic diodes inside the LTM8029 can
R3
R4
pull large currents from the output through the V pin.
IN
RUN
Figure 2 shows a circuit that will run only when the input
voltage is present and that protects against a shorted or
reversed input.
8029 F01
Figure 1. R3 and R4 Set the Minimum
Operating Threshold Voltage
LTM8029
V
V
OUT
V
IN
V
OUT
IN
Minimum Input Voltage
RUN
BIAS
The LTM8029 is a step-down converter, so a minimum
amount of headroom is required to keep the output in
regulation. Curves detailing the minimum input voltage
of the LTM8029 for various load conditions are included
in the Typical Performance Characteristics section.
RT
FB
GND
8029 F02
The LTM8029 features the ability to skip the off-time in
switching cycle when the input voltage approaches the
targetoutput.ThisallowstheLTM8029tooperateaninput
voltageslowerthanotherstep-downregulators.Graphsof
minimuminputvoltageversusoutputvoltageandloadare
given in the Typical Performance Characteristics section.
Figure 2. The Input Diode Prevents Shorted Input from
Discharging a Backup Battery Tied to the Output. It
Also Protects the Circuit from a Reversed Input. The
LTM8029 Runs Only When the Input is Present
8029fa
13
LTM8029
applicaTions inForMaTion
Power Good
1. Place the R and R resistors as close as possible to
FB T
their respective pins.
The PGOOD pin is the open-collector output of an internal
comparator that monitors the voltage at the FB pin. It
is used to indicate whether the output is near or within
regulation. Specifically, PGOOD islowunlessthe FBpin is
within 10% of the final regulation voltage. PGOOD output
2. Place the C capacitor as close as possible to the V
IN
IN
and GND connection of the LTM8029.
3. Place the C
capacitor as close as possible to the
OUT
V
and GND connection of the LTM8029.
OUT
is valid when V is above 4.5V and RUN is high. If this
IN
4. Place the C and C
capacitors such that their
OUT
function is not used, leave this pin floating.
IN
ground currents flow directly adjacent or underneath
Hot-Plugging Safely
the LTM8029.
The small size, robustness and low impedance of ceramic
capacitors make them an attractive option for the input
bypass capacitor of LTM8029. However, these capacitors
can cause problems if the LTM8029 is hot-plugged into
a live supply (see Application Note 88 for a complete dis-
cussion). The low loss ceramic capacitor combined with
stray inductance in series with the power source forms an
5. Connect all of the GND connections to as large a copper
pour or plane area as possible on the top layer. Avoid
breaking the ground connection between the external
components and the LTM8029.
6. For good heat sinking, use vias to connect the GND cop-
per area to the board’s internal ground planes. Liberally
distributetheseGNDviastoprovidebothagoodground
connectionandthermalpathtotheinternalplanesofthe
printed circuit board. Pay attention to the location and
density of the thermal vias in Figure 3. The LTM8029
can benefit from the heat sinking afforded by vias that
connect to internal GND planes at these locations, due
to their proximity to internal power handling compo-
nents. The optimum number of thermal vias depends
upon the printed circuit board design. For example, a
board might use very small via holes. It should employ
more thermal vias than a board that uses larger holes.
underdamped tank circuit, and the voltage at the V pin
IN
of the LTM8029 can ring to more than twice the nominal
input voltage, possibly exceeding the LTM8029’s rating
and damaging the part. If the input supply is poorly con-
trolled or the user will be hot-plugging the LTM8029 into
anenergizedsupply,theinputnetworkshouldbedesigned
to prevent this overshoot. This can be accomplished by
installing a small resistor in series to V , but the most
IN
popular method of controlling input voltage overshoot is
to add an electrolytic bulk capacitor to the V net. This
IN
capacitor’s relatively high equivalent series resistance
usually damps the circuit and eliminates the voltage
overshoot. The extra capacitor improves low frequency
ripple filtering and can slightly improve the efficiency of
the circuit, though it is likely to be the largest component
in the circuit.
V
IN
V
OUT
C
IN
GND
BIAS
C
PCB Layout
OUT
PGOOD
RUN
Most of the headaches associated with PCB layout have
been alleviated or even eliminated by the high level of
integration of the LTM8029. The LTM8029 is neverthe-
less a switching power supply, and care must be taken to
minimize EMI and ensure proper operation. Even with the
high level of integration, you may fail to achieve specified
operation with a haphazard or poor layout. See Figure 3
for a suggested layout. Ensure that the grounding and
heat sinking are acceptable.
GND
R
R
T
FB
THERMAL VIAS
8029 F03
Figure 3. Layout Showing Suggested External
Components, GND Plane and Thermal Vias
8029fa
14
LTM8029
applicaTions inForMaTion
Thermal Considerations
While the meaning of each of these coefficients may seem
to be intuitive, JEDEC has defined each to avoid confusion
and inconsistency. These definitions are given in JESD
51-12, and are quoted or paraphrased below:
The LTM8029 output current may need to be derated if
it is required to operate in a high ambient temperature or
deliver a large amount of continuous power. The amount
of current derating is dependent upon the input voltage,
output power and ambient temperature. The temperature
rise curves given in the Typical Performance Character-
istics section can be used as a guide. These curves were
•ꢀ θ is the natural convection junction-to-ambient air
JA
thermal resistance measured in a one cubic foot sealed
enclosure.Thisenvironmentissometimesreferredtoas
“still air” although natural convection causes the air to
move.Thisvalueisdeterminedwiththepartmountedto
a JESD 51-9 defined test board, which does not reflect
an actual application or viable operating condition.
2
generated by a LTM8029 mounted to a 40cm 4-layer FR4
printedcircuitboard. Boardsofothersizesandlayercount
can exhibit different thermal behavior, so it is incumbent
upon the user to verify proper operation over the intended
system’sline,loadandenvironmentaloperatingconditions.
•ꢀ θ
isthethermalresistancebetweenthejunction
JCbottom
and bottom of the package with all of the component
power dissipation flowing through the bottom of the
package. In the typical µModule converter, the bulk of
the heat flows out the bottom of the package, but there
is always heat flow out into the ambient environment.
As a result, this thermal resistance value may be useful
for comparing packages but the test conditions don’t
generally match the user’s application.
The thermal resistance numbers listed in the Pin Con-
figuration are based on modeling the µModule package
mounted on a test board specified per JESD 51-9 (“Test
Boards for Area Array Surface Mount Package Thermal
Measurements”).Thethermalcoefficientsprovidedinthis
page are based on JESD 51-12 (“Guidelines for Reporting
and Using Electronic Package Thermal Information”).
Forincreasedaccuracyandfidelitytotheactualapplication,
many designers use FEA to predict thermal performance.
To that end, the Pin Configuration section typically gives
four thermal coefficients:
•ꢀ θ
is determined with nearly all of the component
JCtop
power dissipation flowing through the top of the pack-
age.AstheelectricalconnectionsofthetypicalµModule
converter are on the bottom of the package, it is rare
for an application to operate such that most of the heat
flows from the junction to the top of the part. As in the
•ꢀ θ – Thermal resistance from junction to ambient
JA
•ꢀ θ
– Thermal resistance from junction to the
caseofθ
,thisvaluemaybeusefulforcomparing
JCbottom
JCbottom
bottom of the product case
packages but the test conditions don’t generally match
the user’s application.
•ꢀ θ – Thermal resistance from junction to top of the
JCtop
product case
•ꢀ θ is the junction-to-board thermal resistance where
JB
almost all of the heat flows through the bottom of the
•ꢀ θ – Thermal resistance from junction to the printed
JB
µModule converter and into the board, and is really
circuit board
the sum of the θ
and the thermal resistance
JCbottom
of the bottom of the part through the solder joints and
throughaportionoftheboard.Theboardtemperatureis
measured a specified distance from the package, using
a two sided, two layer board. This board is described
in JESD 51-9.
8029fa
15
LTM8029
applicaTions inForMaTion
Giventhesedefinitions,itshouldnowbeapparentthatnone
of these thermal coefficients reflects an actual physical
operating condition of a µModule converter. Thus, none
of them can be individually used to accurately predict the
thermal performance of the product. Likewise, it would
be inappropriate to attempt to use any one coefficient to
correlate to the junction temperature vs load graphs given
in the product’s data sheet. The only appropriate way to
use the coefficients is when running a detailed thermal
analysis, such as FEA, which considers all of the thermal
resistances simultaneously.
The blue resistances are contained within the µModule
converter, and the green are outside.
The die temperature of the LTM8029 must be lower than
the maximum rating of 125°C, so care should be taken in
the layout of the circuit to ensure good heat sinking of the
LTM8029. The bulk of the heat flow out of the LTM8029
is through the bottom of the μModule converter and the
BGA pads into the printed circuit board. Consequently a
poor printed circuit board design can cause excessive
heating, resulting in impaired performance or reliability.
Please refer to the PCB Layout section for printed circuit
board design suggestions.
A graphical representation of these thermal resistances
is given in Figure 4.
JUNCTION-TO-AMBIENT RESISTANCE (JESD 51-9 DEFINED BOARD)
JUNCTION-TO-CASE (TOP)
RESISTANCE
CASE (TOP)-TO-AMBIENT
RESISTANCE
JUNCTION-TO-BOARD RESISTANCE
JUNCTION
AMBIENT
JUNCTION-TO-CASE
(BOTTOM) RESISTANCE
CASE (BOTTOM)-TO-BOARD
RESISTANCE
BOARD-TO-AMBIENT
RESISTANCE
8029 F04
µMODULE DEVICE
Figure 4. Graphical Representation of JESD 51-12 Thermal Coefficients
8029fa
16
LTM8029
applicaTions inForMaTion
1.2V Step-Down Converter
2.5V Step-Down Converter
LTM8029
LTM8029
V
V
V
IN
V
IN
OUT
OUT
V
V
OUT
V
V
OUT
IN
IN
4.5V TO 12V
4.5V TO 36V
2.5V
1.2V
600mA
600mA
RUN
BIAS
RUN
BIAS
2.2µF
47µF
1µF
47µF
PGOOD
PGOOD
RT
GND FB
RT
GND FB
8029 TA02
8029 TA03
309k
280k
931k
5V Step-Down Converter
LTM8029
V
V
IN
OUT
V
V
OUT
IN
7.8V TO 36V
5V
600mA
RUN
BIAS
1µF
22µF
PGOOD
RT
GND FB
8029 TA04
158k
309k
–5V Inverting Output Converter
Minimum VIN vs Output Current
12
10
8
LTM8029
V
IN
V
V
OUT
IN
4.5V TO 31V
RUN
BIAS
2.2µF
PGOOD
47µF
6
TO START
RUNNING
RT
GND FB
4
158k
309k
V
OUT
2
–5V
0
0
100
200
300
400
500
600
OUTPUT CURRENT (mA)
8029 TA06
8029fa
17
LTM8029
package DescripTion
Table 3. Pin Assignment Table (Arranged by Pin Number)
PIN
A1
A2
A3
A4
A5
FUNCTION
PIN
B1
B2
B3
B4
B5
FUNCTION
PIN
C1
C2
C3
C4
C5
FUNCTION
PIN
D1
D2
D3
D4
D5
FUNCTION
GND
RUN
FB
RT
PGOOD
–
GND
GND
–
GND
–
GND
V
V
V
IN
V
IN
–
GND
IN
IN
–
GND
PIN
E1
E2
E3
E4
E5
FUNCTION
GND
PIN
F1
F2
F3
F4
F5
FUNCTION
GND
PIN
G1
G2
G3
G4
G5
FUNCTION
GND
PIN
H1
H2
H3
H4
H5
FUNCTION
GND
GND
GND
GND
GND
GND
V
OUT
V
OUT
V
OUT
V
OUT
V
OUT
V
OUT
BIAS
GND
V
V
OUT
OUT
GND
8029fa
18
LTM8029
package DescripTion
BGA Package
35-Lead (11.25mm × 6.25mm × 3.42mm)
(Reference LTC DWG # 05-08-1878 Rev Ø)
/ / b b b
Z
2 . 5 4 0
1 . 2 7 0
0 . 3 1 7 5
0 . 3 1 7 5
0 . 0 0 0
1 . 2 7 0
2 . 5 4 0
8029fa
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
19
LTM8029
Typical applicaTion
–12V Inverting Output Converter
Minimum VIN vs Output Current,
–12VOUT, BIAS = GND
25
20
15
10
5
LTM8029
V
IN
V
V
OUT
IN
4.5V TO 31V
RUN
BIAS
2.2µF
PGOOD
22µF
RT
GND FB
137k
110k
V
OUT
TO START
RUNNING
–12V
8029 TA07a
0
0
100
200
300
400
500
OUTPUT CURRENT (mA)
8029 TA07b
package phoTo
relaTeD parTs
3.42mm
mm
PART NUMBER
LTM8020
DESCRIPTION
COMMENTS
4V ≤ V ≤ 36V, 1.25V ≤ V
36V, 200mA µModule Regulator
36V, 500mA µModule Regulator
36V, 1A µModule Regulator
36V, 2A µModule Regulator
Isolated µModule Regulator
≤ 5V
OUT
IN
LTM8021
3V ≤ V ≤ 36V, 0.8V ≤ V
≤ 5V
IN
OUT
LTM8022
3.6V ≤ V ≤ 36V, 0.8V ≤ V
≤ 10V
≤ 10V
IN
OUT
LTM8023
3.6V ≤ V ≤ 36V, 0.8V ≤ V
IN
OUT
LTM8048
725V Isolation, 3.1V ≤ V ≤ 32V, 300mA
DC IN
8029fa
LT 0812 REV A • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
20
●
●
LINEAR TECHNOLOGY CORPORATION 2012
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
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