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, Linear Technology and the Linear logo are registered trademarks and
ThinSOT is a trademark 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.
n
n
n
n
n
n
n
n
n
n
n
Three Independent Current Mode Buck DC/DC
Regulators (1.2A and 2
×
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-Skipping 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, 3mm
×
4mm 20-Lead QFN and
Thermally Enhanced TSSOP FE-16 Packages
Portable Applications with Multiple Supply Rails
General Purpose Step-Down DC/DC
Dynamic Voltage Scaling Applications
applicaTions
n
n
n
Typical applicaTion
V
IN
22µF SV
IN
PV
IN
EN1
EN2
EN3
R
T
FB2
PGOOD
2.5µH**
SW3
20pF
* WURTH 7440430022
** WURTH 744031002
FB3
SGND
PGND
300k
3569 TA01a
2.2µH*
SW1
20pF
FB1
LTC3569
SW2
20pF
300k
240k
240k
2.5µH**
510k
10µF
OUT1 = 2.5V
1200mA
100
90
80
EFFICIENCY (%)
Efficiency vs Load Current
V
IN
= 3V
MODE
OUT2 = 1.8V
600mA
4.7µF
70
60
50
40
30
20
10
0
0.01
0.1
1
V
IN
= 5V
150k
OUT3 = 1.2V
600mA
4.7µF
Burst Mode OPERATION
PULSE-SKIPPING
OUT1 = 2.5V
10
100
I
LOAD
(mA)
1000 10000
3569 TA01b
3569fe
For more information
www.linear.com/LTC3569
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
PGOOD Current ...................................................... ±1mA
Operating Junction Temperature Range
(Notes 6, 7) ............................................ –40°C to 125°C
Storage Temperature Range .................. –65°C to 125°C
Peak Reflow Temperature ..................................... 260°C
pin conFiguraTion
TOP VIEW
PV
IN1
PV
IN3
SW1
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
PGND2 1
SW2 2
PV
IN2
3
PGOOD 4
MODE 5
R
T
6
7
FB2
8
FB1
9 10
FB3
SV
IN
21
GND
PGND1
TOP VIEW
PGND2
PGND1
PV
IN1
SV
IN
PV
IN3
15 SW3
14 PGND3
21
13 EN1
12 EN2
11 EN3
6
FB2
7
FB1
8
FB3
9 10
SGND
SW1
20 19 18 17
16 SW3
15 PGND3
14 EN1
13 EN2
12 EN3
11 SGND
SW2 1
PV
IN2
2
PGOOD 3
MODE 4
R
T
5
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
*SHARES POWER WITH PV
IN3
UDC PACKAGE
20-LEAD (3mm
×
4mm) PLASTIC QFN
T
JMAX
= 125°C,
θ
JA
= 43°C/W
EXPOSED PAD (PIN 21) 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
LTC3569EUDC#PBF
LTC3569IUDC#PBF
LTC3569EFE#PBF
LTC3569IFE#PBF
TAPE AND REEL
LTC3569EUD#TRPBF
LTC3569IUD#TRPBF
LTC3569EUDC#TRPBF
LTC3569IUDC#TRPBF
LTC3569EFE#TRPBF
LTC3569IFE#TRPBF
PART MARKING*
LDQF
LDQF
LFYW
LFYW
3569FE
3569FE
PACKAGE DESCRIPTION
20-Lead (3mm
×
3mm) Plastic QFN
20-Lead (3mm
×
3mm) Plastic QFN
20-Lead (3mm
×
4mm) Plastic QFN
20-Lead (3mm
×
4mm) Plastic QFN
16-Lead Plastic TSSOP
16-Lead Plastic TSSOP
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
–40°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.
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/
3569fe
2
For more information
www.linear.com/LTC3569
LTC3569
elecTrical characTerisTics
SYMBOL
SV
IN
I
VIN
PARAMETER
Input Supply Voltage
Input Current Pulse-Skipping Mode
Input Current Burst Mode Operation
I
QX
Additional Input Current per Buck,
Pulse Skipping
Additional Input Current per Buck,
Burst Mode Operation
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
∆V
LINEREG
∆V
LOADREG
t
SS
t
EN
t
OFF
t
PW
I
ENX
I
MODE
V
IL
V
IH
T
MODEPW
PGOOD
T
PGOOD
Quiescent Current 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
Power Good Threshold
PGOOD Delay
V
FBX
Ramping Up
V
FBX
Ramping Down
Turn-On
Turn-Off
V
ENX
= 3.6V
V
MODE
= 3.6V
MODE, ENx
MODE, ENx
1.2
100
–8
–12
8
2
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
= 1.8V, 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
)
SV
IN
= 2.5V to 5.5V
Pulse-Skipping 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
junction 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
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
%
%
µs
µs
3569fe
EN1 = SV
IN
, EN2, EN3 = MODE = 0V,
I
OUT1
, = 0A, FB1 = 0.9V (Note 3)
EN1 = MODE = SV
IN
, EN2, EN3 = 0V,
I
OUT1
, = 0A, FB1 = 0.9V (Note 3)
MODE = 0V, I
OUTX
, = 0A, FBx = 0.9V
(Note 3)
MODE = SV
IN
, I
OUTX
, = 0A,
FBx = 0.9V (Note 3)
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
2.0
1.0
0.8
25
0.425
For more information
www.linear.com/LTC3569
3
LTC3569
The
l
denotes the specifications which apply over the full operating
junction temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 3.6V unless otherwise noted (Notes 2, 7).
SYMBOL
R
PGOOD
UVLO
f
OSC
f
CLK(MAX)
f
CLK(MIN)
f
SYNC
PARAMETER
PGOOD Pull-Down On-Resistance
Undervoltage Lockout
Fixed Oscillator Frequency
Minimum Programmable Oscillator Frequency
Sync Frequency
V
RT
= SV
IN
R
T
= 453k
V
RT
= SV
IN
R
T
= 453k
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.
1.2
Maximum Programmable Oscillator Frequency R
T
= 100k
CONDITIONS
V
FBX
< 0.4V
l
l
l
l
elecTrical characTerisTics
MIN
TYP
380
MAX
525
2.5
2.8
1.0
3
UNITS
Ω
V
MHz
MHz
MHz
MHz
MHz
1.9
3.0
2.25
Note 6:
This IC includes overtemperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature exceeds 125°C when overtemperature protection is active.
Continuous operation above the specified maximum operating junction
temperature may impair device reliability.
Note 7:
The LTC3569 is tested under pulsed load conditions such that
T
J
≈ T
A
. The LTC3569E is guaranteed to meet specified performance from
0°C to 85°C. Specifications over the –40°C to 125°C operating junction
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 125°C operating junction
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