FEATURES
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LTC3569
Triple Buck Regulator With
1.2A and Two 600mA Outputs and
Individual Programmable References
DESCRIPTION
The LTC
®
3569 contains three monolithic, synchronous
step-down DC/DC converters. Intended for medium power
applications, it operates over a 2.5V to 5.5V input voltage
range. The operating frequency is adjustable from 1MHz
to 3MHz, allowing the use of tiny, low cost capacitors and
inductors. The three output voltages are independently
programmable by toggling the EN pins up to 15 times,
lowering the 800mV FB references by 25mV per cycle. The
first buck regulator sources load currents up to 1200mA.
The other two buck regulators each provide 600mA.
The two 600mA buck regulators can also be configured
to operate as slave power stages, running in parallel with
another internal buck regulator to supply higher load
currents. When operating as parallel, slave output stages,
discrete external components are shared and available
output currents sum together.
L,
LT, LTC, LTM and Burst Mode are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners. Protected by U.S. Patents
including 5481178, 6127815, 6304066, 6498466, 6580258, 6611131, 7170195.
Three Independent Current Mode Buck DC/DC
Regulators (1.2A and 2x 600mA)
Single Pin Programmable V
FB
Servo Voltages from
800mV Down to 425mV (in 25mV Steps)
Pull V
FB
High to Make Each 600mA Buck a Slave for
Higher Current Operation
Pulse Skip or Burst Mode
®
Operation
Programmable Switching Frequency
(1MHz to 3MHz) or Fixed 2.25MHz
Synchronizable (1.2MHz to 3MHz)
V
IN
Range 2.5V to 5.5V
All Regulators Internally Compensated
PGOOD Output Flag
Quiescent Current <100μA (All Regulators in Burst
Mode Operation)
Zero Shutdown Current
Overtemperature and Short-Circuit Protection
Tiny 3mm
×
3mm 20-Lead QFN and Thermally
Enhanced TSSOP FE-16 Packages
APPLICATIONS
n
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Portable Applications with Multiple Supply Rails
General Purpose Step-Down DC/DC
Dynamic Voltage Scaling Applications
TYPICAL APPLICATION
V
IN
22μF SV
IN
PV
IN
EN1
EN2
EN3
R
T
FB2
PGOOD
2.5μH
SW3
20pF
FB3
SGND
PGND
300k
3569 TA01a
2.2μH
SW1
20pF
FB1
240k
2.5μH
SW2
20pF
300k
240k
510k
10μF
Efficiency vs Load Current
OUT1 = 2.5V
1200mA
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
OUT3 = 1.2V
600mA
4.7μF
10
0
0.01
0.1
1
10
100
I
LOAD
(mA)
BURST
PULSE SKIP
OUT1 = 2.5V
1000 10000
3569 TA01b
V
IN
= 3V
LTC3569
OUT2 = 1.8V
600mA
4.7μF
V
IN
= 5V
MODE
150k
3569f
1
LTC3569
ABSOLUTE MAXIMUM RATINGS
(Notes 1, 6)
SV
IN
Voltage.......................... –0.3V to 6V (7V Transient)
PV
INX
Voltage .........................S
VIN
– 0.3V to S
VIN
+ 0.3V
ENx, MODE, PGOOD, SWx, FBx ......–0.3V to S
VIN
+ 0.3V
R
T
Voltage .................................................... –0.3V to 6V
I
SW1
(DC) .................................................................2.5A
I
SW2
, I
SW3
(DC) ........................................................1.3A
Operating Temperature Range.................. –40°C to 85°C
Storage Temperature Range................... –65°C to 125°C
Maximum Junction Temperature (Note 6) ............ 125°C
Peak Reflow Temperature ..................................... 260°C
PIN CONFIGURATION
PGND2
PGND1
TOP VIEW
FB3
SV
IN
SGND
EN3
EN2
EN1
SW3
PV
IN1
1
2
3
4
5
6
7
8
17
16 FB1
15 FB2
14 R
T
13 MODE
12 PGOOD
11 PV
IN2
10 SW2
9
SW1
SW2 1
PV
IN2
2
PGOOD 3
MODE 4
R
T
5
6
FB2
7
FB1
8
FB3
9 10
SV
IN
SGND
21
TOP VIEW
PV
IN1
PV
IN3
15 SW3
14 PGND3
13 EN1
12 EN2
11 EN3
SW1
20 19 18 17 16
FE PACKAGE
16-LEAD PLASTIC TSSOP
T
JMAX
= 125°C,
θ
JA
= 38°C/W
EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB
UD PACKAGE
20-LEAD (3mm
×
3mm) PLASTIC QFN
T
JMAX
= 125°C,
θ
JA
= 68°C/W
EXPOSED PAD (PIN 21) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LTC3569EUD#PBF
LTC3569IUD#PBF
LTC3569EFE#PBF
LTC3569IFE#PBF
TAPE AND REEL
LTC3569EUD#TRPBF
LTC3569IUD#TRPBF
LTC3569EFE#TRPBF
LTC3569IFE#TRPBF
PART MARKING
LDQF
LDQF
3569FE
3569FE
PACKAGE DESCRIPTION
20-Lead (3mm
×
3mm) Plastic QFN
20-Lead (3mm
×
3mm) Plastic QFN
16-Lead Plastic TSSOP
16-Lead Plastic TSSOP
TEMPERATURE RANGE
–40°C to 85°C
–40°C to 85°C
–40°C to 85°C
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to:
http://www.linear.com/tapeandreel/
3569f
2
LTC3569
ELECTRICAL CHARACTERISTICS
SYMBOL
SV
IN
I
VIN
I
QX
PARAMETER
Input Supply Voltage
Input Current Pulse Skip Mode
Input Current Burst Mode Operation
Additional Input Current per Buck,
Pulse Skip
Burst Mode Operation
Quiescent Current at SGND Pin in Shutdown
Mode
Peak Inductor Current SW1
Peak Inductor Current SW2, SW3
Maximum Feedback Voltage
Feedback Reference Step Size
Minimum Feedback Voltage
Feedback Programming Range
Feedback Pin Input Current
Switch Pin Leakage Current
Maximum Duty Cycle
R
DSON
of PSW for SW1
R
DSON
of NSW for SW1
R
DSON
of PSW for SW2, SW3
R
DSON
of NSW for SW2, SW3
SWx Pull-Down in Shutdown
Reference Voltage Line Regulation
Output Voltage Load Regulation
Soft Start Reference Ramp Rate
Enable Turn-On Delay
Enable Turn-Off Delay
Enable Pulse Width
Enable Leakage Current
Mode Leakage Current
Input Low Voltage
Input High Voltage
Pulse Width Applied to MODE Pin for
Synchronizing
V
ENX
= 3.6V
V
MODE
= 3.6V
MODE, ENx
MODE, ENx
1.2
100
From Last ENx Rise to Begin of Soft
Start Ramp
From ENx Fall to Shutdown
0.06
0.02
0.02
0.4
V
FB
= 0.8V
V
SWX
= 0V or SV
IN
, V
ENX
= SV
IN
,
V
FBX
= 0.9V
FBx = 0V
I
SW1
= 100mA (Note 5)
I
SW1
= –100mA (Note 5)
I
SW2
, I
SW3
= 100mA (Note 5)
I
SW2
, I
SW3
= –100mA (Note 5)
ENx = 0V, V
SWX
= 1.2V,
(FBx < SV
IN
)
S
VIN
= 2.5V to 5.5V
Pulse Skip Mode (Note 4)
100
195
180
265
250
2.3
0.04
0.5
0.75
125
170
240
330
55
0.2
l
l
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 3.6V unless otherwise noted (Notes 2, 7).
CONDITIONS
l
MIN
2.5
TYP
230
47
140
22
0.1
MAX
5.5
365
82
225
36
1
2.5
1.3
0.816
0.44
0.8
±0.2
±1
UNITS
V
μA
μA
μA
μA
A
A
V
mV
V
V
μA
μA
%
mΩ
mΩ
mΩ
mΩ
kΩ
%/V
%
V/ms
μs
μs
μs
μA
μA
V
V
ns
EN1 = S
VIN
, EN2, EN3 = 0, I
OUT1
, = 0A,
FB1 = 0.9V (Note 3)
(Note 3) V
FB
= 0.9V
EN1, EN2, EN3 = 0V
V
SW1
= V
SW2
= V
SW3
= 0V
1.8
0.780
0.784
0.405
0.425
Each Toggle on ENx
ENx Toggle 15 Times
l
I
QSHDN
I
PK1
I
PK2
, I
PK3
V
FBX(MAX)
V
FBX(STEP)
V
FBX(MIN)
V
PROGFBX
I
FBX
I
LKSWX
D
X
R
P1
R
N1
R
P2
, R
P3
R
N2
, R
N3
RSWx_PD
ΔV
LINEREG
ΔV
LOADREG
t
SS
t
EN
t
OFF
t
PW
I
ENX
I
MODE
V
IL
V
IH
T
MODEPW
2.0
1.0
0.8
25
0.425
3569f
3
LTC3569
ELECTRICAL CHARACTERISTICS
SYMBOL
PGOOD
T
PGOOD
R
PGOOD
UVLO
f
OSC
f
CLK(MAX)
f
CLK(MIN)
f
SYNC
PARAMETER
Power Good Threshold
PGOOD Delay
PGOOD Pull-Down On-Resistance
Undervoltage Lockout
Fixed Oscillator Frequency
Minimum Programmable Oscillator Frequency
Sync Frequency
V
RT
= S
VIN
R
T
= 453k
R
T
= 100k
Maximum Programmable Oscillator Frequency R
T
= 100k
V
FBX
< 0.4V
l
l
l
l
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 3.6V unless otherwise noted (Notes 2, 7).
CONDITIONS
V
FBX
Ramping Up
V
FBX
Ramping Down
MIN
TYP
–8
–12
2
380
1.9
3.0
1.0
1.2
3
2.25
525
2.5
2.8
MAX
UNITS
%
%
μs
Ω
V
MHz
MHz
MHz
MHz
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:
Current into a pin is positive and current out of a pin is negative.
All voltages referenced to SGND.
Note 3:
Dynamic supply current is higher due to the internal gate charge
being delivered at the switching frequency.
Note 4:
Specification is guaranteed by design and not 100% tested in
production.
Note 5:
Switch on-resistance verified by correlation to wafer level
measurements.
Note 6:
This IC includes over-temperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature exceeds 125°C when over-temperature protection is active.
Continuous operation above the specified maximum operating junction
temperature may impair device reliability.
Note 7:
The LTC3569E is guaranteed to meet specified performance from
0°C to 85°C. Specifications over the –40°C to 85°C operating temperature
range are assured by design characterization and correlation with
statistical process controls. The LTC3569I is guaranteed to meet specified
performance over the full –40°C to 85°C operating temperature range.
TYPICAL PERFORMANCE CHARACTERISTICS
I
SVIN
vs Temperature
300
250
200
I
SVIN
(μA)
150
100
50
0
–50
BUCK1 ONLY Burst Mode OPERATION
V
IN
= 3.5V
SLOPE
≅
132nA/°C
0
NO LOAD
150
3569 G01
T
A
= 25°C, unless otherwise noted.
Efficiency vs Load Current
OUT3 = 1.2V
100
90
80
EFFICIENCY (%)
V
IN
= 3V
Efficiency vs Load Current
OUT2 = 1.8V
100
90
V
IN
= 3V
BUCK1 ONLY PULSE SKIP V
IN
= 3.5V
EFFICIENCY (%)
80
70
60
50
40
30
20
10
0
0.01
0.1
1
10
I
LOAD
(mA)
BURST
PULSE SKIP
100
1000
3569 G02
SLOPE
≅
185nA/°C
V
IN
= 5V
70
60
50
40
30
20
10
0
0.01
0.1
1
10
I
LOAD
(mA)
BURST
PULSE SKIP
100
1000
3569 G03
V
IN
= 5V
50
100
TEMPERATURE (°C)
3569f
4
LTC3569
TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency vs V
SUPPLY
OUT1 = 1.8V
95
90
EFFICIENCY (%)
EFFICIENCY (%)
85
80
75
70
65
I
LOAD
= 270mA
I
LOAD
= 220mA
I
LOAD
= 170mA
I
LOAD
= 120mA
2
3
4
V
SUPPLY
(V)
3569 G04
T
A
= 25°C, unless otherwise noted.
Efficiency vs V
SUPPLY
OUT3 = 1.5V
Efficiency vs V
SUPPLY
OUT2 = 1.2V
BUCK1 ONLY
95
90
EFFICIENCY (%)
85
80
75
70
65
I
LOAD
= 210mA
I
LOAD
= 170mA
I
LOAD
= 110mA
I
LOAD
= 70mA
2
3
4
V
SUPPLY
(V)
3569 G05
BUCK2 ONLY
95
90
85
80
75
70
65
I
LOAD
= 210mA
I
LOAD
= 170mA
I
LOAD
= 110mA
I
LOAD
= 70mA
2
3
4
V
SUPPLY
(V)
BUCK3 ONLY
5
6
5
6
5
6
3569 G06
Oscillator Frequency
vs Temperature
2.40
V
IN
= 5.5V
2.30
f
CLK
(MHz)
V
IN
= 3.5V
R
DS(ON)
(Ω)
0.30
0.35
R
DS(ON)
SW1
vs V
SUPPLY
and Temperature
100°C
25°C
0.25
R
DS(ON)
(Ω)
NSW1
PSW1
0.50
0.45
0.40
0.35
0.30
0.25
R
DS(ON)
SW2 and SW3
vs V
SUPPLY
and Temperature
100°C
NSW2 & 3
PSW3 & 3
25°C
2.20
V
IN
= 2.5V
0.20
–50°C
2.10
0.15
V
RT
= SV
IN
0
100
50
TEMPERATURE (°C)
150
3569 G07
0.20
–50°C
0.15
0.10
2
3
4
V
SUPPLY
(V)
3569 G08
2.00
–50
0.10
5
6
2
3
4
V
SUPPLY
(V)
5
6
3569 G09
V
FB
vs Temperature
0.3
V
REF
SET TO MAX
0.2
V
FB
ERROR (%)
0.1
I
SVIN
(μA)
0.0
–0.1
200
–0.2
–0.3
–50
V
FB1
V
FB2
V
FB3
0
100
50
TEMPERATURE (°C)
150
3569 G10
I
SVIN
vs V
SUPPLY
Pulse Skip
700
600
500
400
300
1 BUCK ENABLED
I
SVIN
(μA)
2 BUCKS ENABLED
ALL 3
120
100
80
60
I
SVIN
vs V
SUPPLY
Burst Mode Operation
ALL 3
2 BUCKS ENABLED
1 BUCK ENABLED
40
20
100
0
NO LOAD
2
3
4
V
SUPPLY
(V)
3569 G11
0
6
NO LOAD
2
3
4
V
SUPPLY
(V)
5
6
3569 G12
5
3569f
5
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