LINER LTC3562EUD-TRPBF I2c quad synchronous step-down dc/dc regulator 2 ã 600ma, 2 ã 400ma Datasheet

LTC3562
I2C Quad Synchronous
Step-Down DC/DC Regulator
2 × 600mA, 2 × 400mA
DESCRIPTION
FEATURES
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Four Independent I2C Controllable Step-Down
Regulators (2 × 600mA, 2 × 400mA)
Two I2C Programmable Feedback Voltage
Regulators (R600A, R400A): VFB 425mV to 800mV
Two I2C Programmable Output Voltage Regulators
(R600B, R400B): VOUT 600mV to 3.775V
Programmable Modes: Pulse Skip, LDO, Burst Mode,®
Forced Burst Mode Operation
Quiescent Current < 100μA (All Regulators Enabled
in LDO Mode)
Fixed 2.25MHz Switching Frequency (Pulse Skip
Mode)
Slew Limiting Reduces Switching Noise
Power-On Reset Output for Regulator R600A
Small, Thermally Enhanced, 20-Lead 3mm × 3mm
QFN Package
The LTC®3562 is a quad high efficiency monolithic synchronous step-down regulator with an I2C interface. Two
regulators are externally adjustable and can have their
feedback voltages programmed between 425mV and
800mV in 25mV steps (Type A). The other two regulators
are fixed output regulators whose output voltages can be
programmed between 600mV and 3.775V in 25mV steps
(Type B). All four regulators operate independently and
can be put into pulse skip, LDO, Burst Mode operation,
or forced Burst Mode operation through I2C control. The
Type-A regulators have separate RUN pins that can be
enabled if I2C control is unavailable.
The 2.85V to 5.5V input voltage range makes the LTC3562
ideally suited for single Li-Ion battery-powered applications. At low output load conditions, the regulators can
be switched into LDO, Burst Mode operation, or forced
Burst Mode operation, extending battery life in portable
systems. The quiescent current drops to under 100μA
with all regulators in LDO mode, and under 0.1μA when
all regulators are shut down.
APPLICATIONS
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Miscellaneous Handheld Applications with Multiple
Supply Rails
Personal Information Appliances
Wireless and DSL Modems
Digital Still Cameras
MP3 Players
Portable Instruments
Switching frequency is internally set to 2.25MHz, allowing
the use of small surface mount inductors and capacitors.
All regulators are internally compensated. The LTC3562 is
available in a low profile 3mm × 3mm QFN package.
L, LT, LTC, LTM and Burst Mode are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
R600x Burst Mode Efficiency
and Power Loss vs Load Current
High Efficiency Quad Step-Down Converter with I2C
MICROPROCESSOR
+
10μF
VOUT
400A
1.5V
400mA
4.7μH
RUN400A
SW400A
10μF
10pF
SCL SDA DVCC
475k
FB400A
LTC3562
100k
POR600A
SW600A
3.3μH
VOUT 600A
1.8V
600mA
634k
FB600A
10pF
RUN600A
499k
536k
90
80
10μF
4.7μH
10μF
3.3μH
SW400B
SW600B
OUT400B PGND AGND OUT600B
3562 TA01
VOUT 600B
3.3V
10μF 600mA
VOUT =
2.5V
VOUT = 1.2V
70
1000
VOUT =
1.8V
60
100
50
10
40
30
20
VOUT 400B
1.2V
400mA
10000
VOUT = 3.3V
VOUT = 1.2V,
1.8V, 2.5V
10
0
0.01
VOUT = 3.3V
POWER LOSS (mW)
VIN
100
SDA
SCL
DVCC
POR
EFFICIENCY (%)
Li-Ion/Polymer
3.4V TO 4.2V
1
VIN = 3.8V
0.1
1
10
100
LOAD CURRENT (mA)
0.1
1000
3562 TA01b
3562fa
1
LTC3562
ABSOLUTE MAXIMUM RATINGS
PIN CONFIGURATION
(Notes 1, 2)
RUN400A
RUN600A
DVCC
SCL
SDA
TOP VIEW
20 19 18 17 16
15 POR600A
AGND 1
14 FB600A
FB400A 2
13 OUT600B
21
OUT400B 3
12 SW600B
SW400B 4
11 PGND
7
8
9 10
VIN
VIN
SW600A
6
VIN
PGND 5
SW400A
VIN ............................................................... –0.3V to 6V
RUN600A ...................................... –0.3V to (VIN + 0.3V)
RUN400A ...................................... –0.3V to (VIN + 0.3V)
FBx ............................................................... –0.3V to 6V
SWx ............................................................. –0.3V to 6V
OUTx ............................................................ –0.3V to 6V
DVCC , POR600A, SDA, SCL ......................... –0.3V to 6V
ISW400x (DC) ........................................................600mA
ISW600x (DC) ........................................................850mA
Operating Temperature (Note 2)...............–40°C to 85°C
Storage Temperature Range...................–65°C to 125°C
Junction Temperature (Note 3) ............................. 125°C
UD PACKAGE
20-LEAD (3mm × 3mm) PLASTIC QFN
TJMAX = 125°C, θJA = 68°C/W
EXPOSED PAD (PIN 21) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
TAPE AND REEL
PART MARKING
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC3562EUD#PBF
LTC3562EUD#TRPBF
LCPV
20-Lead (3mm × 3mm) Plastic QFN
–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/
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C, VIN = 3.8V, unless otherwise noted.
PARAMETER
CONDITIONS
l
VIN Input Voltage Range
VIN Input Current (Per Regulator Enabled)
VIN Shutdown Current
MIN
TYP
2.7
MAX
UNITS
5.5
V
Pulse Skip Mode, IOUT = 0
Burst Mode Operation, IOUT = 0
Forced Burst Mode Operation, IOUT = 0
LDO Mode, IOUT = 0
Shutdown Mode, IOUT = 0, DVCC = 1.8V
220
35
25
24
0.7
60
40
40
3
μA
μA
μA
μA
μA
All Regulators in Shutdown, DVCC = 0V
0.1
1
μA
RUN600A, RUN400A Input High Threshold
l
RUN600A, RUN400A Input Low Threshold
l
1.0
V
0.3
V
RUN600A, RUN400A Input High Current
RUNx = VIN
–1
1
μA
RUN600A, RUN400A Input Low Current
RUNx = 0V
–1
1
μA
POR600A Threshold
Percentage of R600A’s Final Output Voltage
–8
POR600A On-Resistance
16
POR600A Delay
231
%
40
Ω
ms
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LTC3562
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C, VIN = 3.8V, unless otherwise noted.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
I2C Port
l
DVCC Operating Voltage
DVCC Operating Current
1.5
DVCC = 1.8V, Serial Port Idle
DVCC UVLO Threshold Voltage
V
1
μA
1
VIL SDA, SCL (Low Level Input Voltage)
V
0.3 • DVCC
VIH SDA, SCL (High Level Input Voltage)
VOL SDA (Digital Output Low)
5.5
0.7 • DVCC
IPULLUP = 3mA
V
V
0.08
V
Serial Port Timing (Note 4)
tSCL
Clock Operating Frequency
tBUF
Bus Free Time Between Stop and Start Conditions
1.3
400
kHz
μs
tHD,STA
Hold Time After (Repeated) Start Condition
0.6
μs
tSU,STA
Repeated Start Condition Setup Time
0.6
μs
tSU,STO
Stop Condition Setup Time
0.6
μs
tHD,DAT(OUT)
Data Hold Time
225
tHD,DAT(IN)
Input Data Hold Time
tSU,DAT
Data Setup Time
100
ns
tLOW
Clock Low Period
1.3
μs
tHIGH
Clock High Period
0.6
μs
tf
Clock Data Fall Time
20
300
ns
tr
Clock Data Rise Time
20
300
ns
tSP
Spike Suppression Time
50
ns
0
900
ns
ns
BUCK DC/DC ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the
full operating temperature range, otherwise specifications are at TA = 25°C, VIN = 3.8V, VOUTx = 1.5V, unless otherwise noted.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
1.91
2.25
2.59
MHz
Regulators R600A, R400A, R600B, R400B
fOSC
Maximum Duty Cycle
Pulse Skip Mode
LDO Mode Closed Loop ROUT
LDO Mode
100
%
Ω
0.25
Regulators R600A, R600B
PMOS Switch Current Limit
Pulse Skip Mode
850
1200
0.38
PMOS RDS(ON)
NMOS RDS(ON)
LDO Mode Open Loop ROUT
LDO Mode
Available Output Current
Forced Burst Mode
LDO, VOUT = 1.2V
SW Pull-Down in Shutdown
Shutdown
75
50
1500
mA
Ω
0.38
Ω
2.2
Ω
140
mA
mA
2.5
kΩ
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LTC3562
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C, VIN = 3.8V, VOUTx = 1.5V, unless otherwise noted.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Pulse Skip Mode
600
800
1000
mA
Regulators R400A, R400B
PMOS Switch Current Limit
PMOS RDS(ON)
0.5
Ω
NMOS RDS(ON)
0.5
Ω
3
Ω
LDO Mode Open Loop ROUT
LDO Mode
SW Pull-Down in Shutdown
Shutdown
Available Output Current
Forced Burst Mode
LDO Mode, VOUT = 1.2V
2.5
kΩ
50
50
100
mA
mA
Regulators R600A, R400A
VFB(MAX)
DAC = XXX1111, Pulse Skip Mode
l
0.776
0.800
0.824
V
VFB(MIN)
DAC = XXX0000, Pulse Skip Mode
l
0.412
0.425
0.438
V
VFB(STEP) (0 to 15)
IFB
25
FB Input Current
DAC = XXX1111
mV
–50
0
50
nA
Regulators R600B, R400B
VOUT(MIN)
VIN = 4V, DAC = 0000000, Pulse Skip Mode
l
0.582
0.600
0.618
V
VOUT(MAX)
VIN = 4V, DAC = 1111111,
Pulse Skip Mode
l
3.661
3.775
3.889
V
VOUT(STEP) (0 to 127)
VIN = 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 LTC3562E is guaranteed to meet performance specifications
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 control.
25
mV
Note 3: This IC includes overtemperature protection that is intended
to protect the device during momentary overload conditions.
Overtemperature protection is active when junction temperature exceeds
the maximum operating junction temperature. Continuous operation above
the specified maximum operating junction temperature may result in
device degradation or failure.
Note 4: The serial port is tested at rated operating frequency. Timing
parameters are tested and/or guaranteed by design.
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LTC3562
TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency vs Load Current
FORCED
Burst Mode OPERATION
80 Burst Mode
70 OPERATION
600mA
BUCKS
50
40
PULSE SKIP
60
20
VIN = 3.8V
VOUT = 1.2V
1
10
IOUT (mA)
100
Burst Mode
OPERATION
40
20
10
PULSE SKIP
50
30
0.1
80
600mA
BUCKS
70
30
0
0.01
100
VIN = 3.8V
VOUT = 1.8V
EFFICIENCY (%)
EFFICIENCY (%)
600mA
BUCKS
PULSE SKIP
Burst Mode
OPERATION
40
0.1
1
10
IOUT (mA)
100
1
10
IOUT (mA)
100
1000
100
VOUT = 1.2V
80
70
70
60
50
40
20
0.1
0.1
1
10
IOUT (mA)
100
0
2.5
3
4
4.5
3.5
INPUT VOLTAGE (V)
VOUT = 1.8V
60
50
40
30
IOUT = 0.1mA
IOUT = 1mA
IOUT = 10mA
IOUT = 100mA
IOUT = 400mA
10
1000
Efficiency vs Input Voltage
Burst Mode Operation
80
30
VIN = 3.8V
VOUT = 3.3V
VIN = 3.8V
VOUT = 2.5V
3562 G03
90
30
0
0.01
0
0.01
1000
90
20
10
40
10
EFFICIENCY (%)
FORCED Burst Mode
90 OPERATION
50
Burst Mode
OPERATION
Efficiency vs Input Voltage
Burst Mode Operation
100
60
PULSE SKIP
50
3562 G02
Efficiency vs Load Current
70
60
30
3562 G01
80
600mA
BUCKS
70
20
10
1000
FORCED
Burst Mode
OPERATION
90
80
60
0
0.01
Efficiency vs Load Current
100
FORCED
Burst Mode OPERATION
90
EFFICIENCY (%)
90
EFFICIENCY (%)
Efficiency vs Load Current
100
EFFICIENCY (%)
100
IOUT = 0.1mA
IOUT = 1mA
IOUT = 10mA
IOUT = 100mA
IOUT = 400mA
20
10
0
5
5.5
2.5
3
4
4.5
3.5
INPUT VOLTAGE (V)
5
5.5
3562 G04
3562 G06
3562 G05
Output Transient
Burst Mode Operation
Output Transient
Pulse Skip Mode
VOUT400B
50mV/DIV
AC
COUPLED
VOUT400B
50mV/DIV
AC
COUPLED
VOUT400A
50mV/DIV
AC
COUPLED
VOUT600B
50mV/DIV
AC
COUPLED
300mA
IOUT400B
5mA
VOUT600A
500mV/DIV
INDUCTOR
CURRENT
IL = 100mA/
DIV
300mA
IOUT400B
5mA
50μs/DIV
VOUT400B = 1.2V
VOUT400A = 1.2V
IOUT400A = 20mA
Start-Up Transient
Pulse Skip Mode
RUN600A OFF
2V/DIV ON
3562 G07
50μs/DIV
VOUT400B = 1.8V
VOUT600B = 1.2V
IOUT600B = 15mA
3562 G08
50μs/DIV
3562 G09
VOUT600A = 1.2V
RLOAD = 6Ω
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LTC3562
TYPICAL PERFORMANCE CHARACTERISTICS
R600A Feedback Voltage
vs Temperature
Output Voltage
vs Load Current (B Version)
1.220
2.5
0.808
2.4
VIN = 5.5V
0.806
2.3
VIN = 3V
0.804
2.2
0.802
0.800
0.798
0.796
VIN = 3.8V
VIN = 2.7V
2.1
2.0
1.9
0.794
1.7
1.6
0.790
–50
–25
25
50
0
TEMPERATURE (°C)
75
1.190
–25
25
50
0
TEMPERATURE (°C)
75
6
IOUT = 0mA
VOUT = 1.2V
Burst Mode Operation
IOUT = 0mA
CURRENT (mA)
35
30
FORCED Burst Mode
OPERATION
CONTINUOUS OPERATION
5
Burst Mode OPERATION
4
3
2
VOUT600A
50mV/DIV
AC
COUPLED
SW
2V/DIV
INDUCTOR
CURRENT
IL = 100mA/
DIV
1
LDO MODE
0
20
2.7
3.1
3.5
3.9 4.3
4.7
VIN VOLTAGE (V)
5.1
4.5
3.5 4
VOLTAGE (V)
400mA – VOUT = 1.2V
600mA – VOUT = 1.2V
400mA – VOUT = 1.8V
600mA – VOUT = 1.8V
3562 G13
2.5
5
3
5.5
PVIN = 3.8V
LOAD = 50mA
6
3562 G14
400mA – VOUT = 2.5V
600mA – VOUT = 2.5V
400mA – VOUT = 3.3V
600mA – VOUT = 3.3V
Output Voltage vs Load Current
Forced Burst Mode Operation
VOUT600A
50mV/DIV
AC
COUPLED
Switch RDS(ON) vs Input Voltage
700
1.22
FORCED
Burst Mode
OPERATION
1.20
600 400mA PMOS
SWITCH RDS(ON) (Ω)
1.21
VOLTAGE (V)
1.19
INDUCTOR
CURRENT
IL = 150mA/
DIV
1.18
1.17
LDO MODE
1.16
1.15
2μs/DIV
PVIN = 3.8V
LOAD = 50mA
3562 G16
3562 G15
2μs/DIV
PULSE SKIP
OPERATION
2
5.5
SW
2V/DIV
600
500
3562 G12
Dynamic Supply Current
vs Input Voltage
40
IIN (μA)
300
400
200
LOAD CURRENT (mA)
3562 G11
Dynamic Supply Current
vs Input Voltage
25
100
0
100
3562 G10
45
PULSE SKIP
1.205
1.195
1.5
–50
100
1.210
1.200
1.8
0.792
VIN = 3.8V
VOUT = 1.2V (TYPE-B)
1.215
VOLTAGE (V)
IOUT = 1mA
fOSC (MHz)
VOLTAGE (mV)
0.810
Oscillator Frequency
vs Temperature
400mA NMOS
600mA PMOS
500
400
600mA NMOS
300
200
1.14
100
VIN = 3.8V
VOUT = 1.2V (TYPE-B)
1.13
1.12
0
20
60
80 100
40
LOAD CURRENT (mA)
0
120
140
3562 G17
2.7
3.1
3.5
3.9 4.3
4.7
VIN VOLTAGE (V)
5.1
5.5
3562 G18
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LTC3562
PIN FUNCTIONS
AGND (Pin 1): Analog Ground Pin. All small-signal components should connect to this ground, which in turn
connects to PGND at one point.
FB400A (Pin 2): Feedback Pin for R400A. When the control loop is complete, this pin servos to 1 of 16 possible
set-points based on the programmed value from the I2C
serial port (see Table 4).
OUT400B (Pin 3): Output Voltage Feedback Pin for
R400B. An I2C programmable internal resistor divider
divides the output voltage down for comparison to the
internal reference voltage. This pin converges to 1 of
128 possible set-points based on the programmed value
from the I2C serial port (see Tables 5 and 6). This node
must be bypassed to GND with a 10μF or greater ceramic
capacitor.
SW400B (Pin 4): Switch Node Connection to the Inductor
for R400B. This pin connects to the drains of the internal
power MOSFET switches of R400B.
PGND (Pins 5, 11): Power Ground Pin. Connect this pin
closely to the (–) terminal of CIN.
SW400A (Pin 6): Switch Node Connection to the Inductor
for R400A. This pin connects to the drains of the internal
power MOSFET switches of R400A.
VIN (Pins 7, 8, 9): Input Supply Pin. This pin must be
closely decoupled to GND with a 10μF or greater ceramic
capacitor.
SW600A (Pin 10): Switch Node Connection to the Inductor
for R600A. This pin connects to the drains of the internal
power MOSFET switches of R600A.
SW600B (Pin 12): Switch Node Connection to the Inductor
for R600B. This pin connects to the drains of the internal
power MOSFET switches of R600B.
OUT600B (Pin 13): Output Voltage Feedback Pin for
R600B. An I2C programmable internal resistor divider
divides the output voltage down for comparison to the
internal reference voltage. This pin converges to 1 of
128 possible set-points based on the programmed value
from the I2C serial port (see Tables 5 and 6). This node
must be bypassed to GND with a 10μF or greater ceramic
capacitor.
FB600A (Pin 14): Feedback Pin for R600A. When the control loop is complete, this pin servos to 1 of 16 possible
set-points based on the programmed value from the I2C
serial port (see Table 4).
POR600A (Pin 15): Power-On Reset for R600A. This opendrain output goes high impedance after a 230ms delay
after the output of R600A reaches 92% of its regulation
voltage. This output gets pulled to GND whenever R600A
falls below 92% of its regulation voltage.
RUN400A (Pin 16): Enable Pin for R400A, Active High.
Apply a voltage greater than 1V to enable this regulator.
RUN600A (Pin 17): Enable Pin for R600A, Active Low.
Apply a voltage less than 0.3V to enable this regulator.
DVCC (Pin 18): Supply Voltage for I2C Lines. This pin sets the
logic reference level of the LTC3562. A UVLO circuit on the
DVCC pin forces all registers to a default setting whenever
DVCC is < 1V. Bypass to GND with a 0.1μF capacitor.
SCL (Pin 19): I2C Clock Input. Serial data is shifted one
bit per clock to control the LTC3562. The logic level for
SCL is referenced to DVCC.
SDA (Pin 20): I2C Data Input. The logic level for SDA is
referenced to DVCC.
Exposed Pad (Pin 21): Ground. Must be soldered to
PCB ground for electrical contact and optimum thermal
performance.
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LTC3562
BLOCK DIAGRAM
17
18
20
19
DVCC
SDA
SCL
DVCC
SDA
16
RUN600A
I
2C
EN
1
SCL MODE DATA
2
VIN
7, 8, 9
RUN400A
4
1
R600A
7
4
D/A
REF600A
EN
0.425V-0.8V
SW600A
10
REF
MODE
FB
FB600A
14
R400A
4
D/A
REF400A
EN
0.425V-0.8V
SW400A
MODE
FB
FB400A
1
6
REF
2
R600B
AGND
1
EN
0.6V
SW600B
12
REF
OUT600B
MODE
13
FB
7
R400B
1
EN
0.6V
SW400B
OUT400B
MODE
15
POR600A
4
REF
3
FB
7
230ms Delay
POWER GOOD
R600A
PGND
5,11
3562 BD
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LTC3562
OPERATION
Introduction
The LTC3562 is a highly integrated power management
IC that contains four I2C controllable, monolithic, high efficiency step-down regulators. Two regulators provide up
to 600mA of output current and the other two regulators
produce up to 400mA. All four regulators are 2.25MHz,
constant-frequency, current mode switching regulators that
can be independently controlled through I2C. All regulators are internally compensated eliminating the need for
external compensation components.
The LTC3562 offers two different types of adjustable
step-down regulators. The two Type-A regulators (R600A,
R400A) can have the feedback voltages adjusted through
I2C from 425mV to 800mV in 25mV increments. The two
Type-B regulators (R600B, R400B) can have the output
voltages adjusted through I2C control from 600mV to
3.775V in 25mV increments.
All four converters support 100% duty cycle operation
(low dropout mode) when their input voltage drops very
close to their output voltage. To suit a variety of applications, four selectable mode functions are available on
the LTC3562’s step-down regulators to trade-off noise
for efficiency.
At moderate to heavy loads, the constant-frequency pulse
skip mode provides the lowest output switching noise solution. At lighter loads, either Burst Mode operation, forced
Burst Mode operation or LDO mode may be selected to
optimize efficiency. The switching regulators also include
soft-start to limit inrush current when powering on, shortcircuit current protection, and switch node slew limiting
circuitry to reduce radiated EMI. No external compensation
components are required.
VFB Adjustable (Type-A) Regulators
The two Type-A step-down regulators (R600A and R400A)
have individual programmable feedback servo voltages via
I2C control. Given a particular feedback servo voltage, the
output voltage is programmed using a resistor divider from
the switching regulator output connected to the feedback
pins (Figure 1). The output voltage is related to the feedback
servo voltage by the following equation:
R1 VOUTxA = VFBxA + 1
R2 Through I2C control, VFBxA can be programmed from
800mV (full scale) down to 425mV in 25mV increments.
When the RUN pins (RUN600A and RUN400A) are used
to activate these regulators, the default feedback servo
voltage is set to 800mV.
LTC3562
L
SWxA
CFB
R1
CO
FBxA
425mV to 800mV
R2
GND
3562 F01
Figure 1. Type-A Regulator Application Circuit
Typical values for R2 are in the range of 40k to 1MΩ. The
capacitor CFB cancels the pole created by the feedback
resistors and the input capacitance of the FB pin and also
helps to improve transient response for output voltages
much greater than 0.8V. A variety of capacitor sizes can be
used for CFB but a value of 10pF is recommended for most
applications. Experimentation with capacitor sizes between
2pF and 22pF may yield improved transient response.
Regulators R600A and R400A have individual RUN pins
that can enable the regulators without accessing the I2C
port. The RUN600A and RUN400A pins are OR’ed with the
enable signals coming from the I2C port (refer to the Block
Diagram) such that regulators R600A and R400A can be
enabled if the I2C port is unavailable. The RUN600A pin is
active low and the RUN400A pin is active high.
When the RUN pins are activated, the Type-A regulators
are enabled in a default setting. The default mode for the
regulators is pulse skip mode and the default feedback
servo voltage setting is 800mV. Once enabled with these
default settings, the settings can always be changed on
the fly through I2C once the I2C terminal is available.
The maximum operating output current of regulators R600A
and R400A are 600mA and 400mA, respectively.
3562fa
9
LTC3562
OPERATION
VOUT Adjustable (Type-B) Regulators
Unlike the Type-A regulators, the two Type-B regulators
do not require an external resistor divider network to
program its output voltage. Regulators R600B and R400B
have feedback resistor networks internal to the chip whose
values can be adjusted through I2C control. These internal feedback resistors can be configured such that the
output voltages can be programmed directly. The output
voltages can be programmed from 600mV to 3.775V in
25mV increments.
Pins OUT600B and OUT400B are feedback sense pins that
connect to the top of the internal resistor divider networks.
These output pins should sense the output voltages of
the regulators right at the output capacitor CO (after the
inductor), as illustrated in Figure 2.
The maximum operating current for regulators R600B and
R400B are 600mA and 400mA, respectively. The Type-B
regulators do not have individual run pins as do the Type-A
regulators. Thus regulators R600B and R400B can only
be enabled through control of the I2C port. When the
part initially powers up, the Type-B regulators default to
shutdown mode and remain disabled until programmed
through I2C.
Regulator Operating Modes
All of the LTC3562’s switching regulators include four
possible operating modes to meet the noise/power needs
of a variety of applications.
In pulse skip mode, an internal latch is set at the start of
every cycle which turns on the main P-channel MOSFET
switch. During each cycle, a current comparator compares
the peak inductor current to the output of an error amplifier.
The output of the current comparator resets the internal
latch which causes the main P-channel MOSFET switch to
turn off and the N-channel MOSFET synchronous rectifier
to turn on. The N-channel MOSFET synchronous rectifier
turns off at the end of the 2.25MHz cycle or if the current
through the N-channel MOSFET synchronous rectifier
drops to zero. Using this method of operation, the error
amplifier adjusts the peak inductor current to deliver the
required output power. All necessary compensation is
internal to the switching regulator requiring only a single
ceramic output capacitor for stability. At light loads in
pulse skip mode, the inductor current may reach zero
on each pulse which will turn off the N-channel MOSFET
synchronous rectifier. In this case, the switch node (SW)
goes high impedance and the switch node voltage will
“ring.” This is discontinuous mode operation, and is
normal behavior for a switching regulator. At very light
loads in pulse skip mode, the switching regulators will
automatically skip pulses as needed to maintain output
regulation. At high duty cycle (VOUT > VIN/2) it is possible
for the inductor current to reverse at light loads, causing
the step-down switching regulator to operate continuously.
When operating continuously, regulation and low noise
output voltage are maintained, but input operating current
will increase to a couple mA.
In forced Burst Mode operation, the switching regulators
use a constant-current algorithm to control the inductor
current. By controlling the inductor current directly and
using a hysteretic control loop, both noise and switching losses are minimized. In this mode output power is
limited. While operating in forced Burst Mode operation,
LTC3562
L
600mV to 3.775V
SWxB
CO
OUTxB
GND
3562 F02
Figure 2. Type-B Regular Application Circuit
3562fa
10
LTC3562
OPERATION
the output capacitor is charged to a voltage slightly higher
than the regulation point. The step-down converter then
goes into sleep mode, during which the output capacitor
provides the load current. In sleep mode, most of the
regulator’s circuitry is powered down, helping conserve
battery power and increase efficiency. When the output
voltage drops below a predetermined value, the switching
regulator circuitry is powered on and another burst cycle
begins. The duration for which the regulator operates in
sleep mode depends on the load current. The sleep time
decreases as the load current increases. Forced Burst Mode
operation has a maximum deliverable output current of
about 140mA for the 600mA regulators and 100mA for
the 400mA regulators. Beyond the maximum deliverable
output current, the step-down switching regulator will not
enter sleep mode and the output will drop out of regulation. Forced Burst Mode operation provides a significant
improvement in efficiency at light loads at the expense of
higher output ripple when compared to pulse skip mode.
For many noise-sensitive systems, forced Burst Mode
operation might be undesirable at certain times (i.e.,
during a transmit or receive cycle of a wireless device),
but highly desirable at others (i.e., when the device is in
low power standby mode). The I2C port can be used to
enable or disable forced Burst Mode operation at any time,
offering both low noise and low power operation when
they are needed.
In Burst Mode operation, the switching regulator automatically switches between fixed frequency pulse skip operation
and hysteretic control as a function of the load current. At
light loads the regulators operate in hysteretic mode and
at heavy loads they operate in constant-frequency mode.
The constant-frequency mode provides the same output
ripple and efficiency as pulse skip mode while hysteretic
mode provides slightly lower output ripple than forced
Burst Mode operation at the expense of slightly lower
efficiency.
Finally, the switching regulators have an LDO mode that
gives a DC option for regulating their output voltages. In
LDO mode, the switching regulators are converted to linear
regulators and deliver continuous power from their SWx
pins through their respective inductors. This mode gives
the lowest possible output noise as well as low quiescent
current at light loads.
Dropout Operation
It is possible for VIN to approach a switching regulator’s
programmed output voltage (e.g., a battery voltage of 3.4V
with a programmed output voltage of 3.3V). When this
happens, the PMOS switch duty cycle increases until it is
turned on continuously at 100%. In this dropout condition, the respective output voltage equals the regulator’s
input voltage minus the voltage drops across the internal
P-channel MOSFET and the inductor.
Soft-Start Operation
Soft-start is accomplished by gradually increasing the
peak inductor current for each switching regulator over
a 500μs period. This allows each output to rise slowly,
helping minimize the battery in-rush current. A softstart cycle occurs whenever a given switching regulator is enabled, or after a fault condition has occurred
(thermal shutdown). A soft-start cycle is not triggered
by changing operating modes. This allows seamless
output operation when transitioning between Burst
Mode operation, forced Burst Mode operation, pulse
skip mode or LDO mode.
Switching Slew Rate Control
The step-down switching regulators contain new patent pending circuitry to limit the slew rate of the switch
node (SWx). This new circuitry is designed to transition
the switch node over a period of a couple nanoseconds,
significantly reducing radiated EMI and conducted supply
noise, while keeping efficiency high.
Step-Down Switching Regulator in Shutdown
The step-down switching regulators are in shutdown when
not enabled for operation. In shutdown, all circuitry in
the step-down switching regulator is disconnected from
the switching regulator input supply, leaving only a few
nano-amps of leakage current. The step-down switching regulator outputs are individually pulled to ground
through a 2k resistor on the switch pin (SWx) when in
shutdown.
3562fa
11
LTC3562
OPERATION
I2C Interface
Acknowledge
The LTC3562 may communicate with a host (master) using
the standard I2C 2-wire interface. The Timing Diagram in
Figure 4 shows the timing relationship of the signals on
the bus. The two bus lines, SDA and SCL, must be high
when the bus is not in use. External pull-up resistors or
current sources, such as the LTC1694 SMBus Accelerator,
are required on these lines. The LTC3562 is a receive-only
(slave) device. The I2C control signals, SDA and SCL are
scaled internally to the DVCC supply. DVCC should be connected to the same power supply as the microcontroller
generating the I2C signals.
The Acknowledge signal is used for handshaking between
the master and the slave. An Acknowledge (active LOW)
generated by the slave (LTC3562) lets the master know
that the latest byte of information was received. The
Acknowledge-related clock pulse is generated by the
master. The master releases the SDA line (HIGH) during
the Acknowledge clock cycle. The slave-receiver must pull
down the SDA line during the Acknowledge clock pulse
so that it remains a stable low during the high period of
this clock pulse.
The I2C port has an undervoltage lockout on the DVCC
pin. When DVCC is below approximately 1V, the I2C serial
port is cleared and the two switching Type-A regulators
are set to full scale.
Slave Address Byte
Bus Speed
The I2C port is designed to be operated at speeds of up
to 400kHz. It has built-in timing delays to ensure correct
operation when addressed from an I2C compliant master
device. It also contains input filters designed to suppress
glitches should the bus become corrupted.
START and STOP Conditions
A bus master signals the beginning of a communication
to a slave device by transmitting a start condition. A start
condition is generated by transitioning SDA from high
to low while SCL is high. When the master has finished
communicating with the slave, it issues a stop condition
by transitioning SDA from low to high while SCL is high.
The bus is then free for communication with another I2C
device.
Byte Format
Each byte sent to the LTC3562 must be 8 bits long followed by an extra clock cycle for the Acknowledge bit to
be returned by the LTC3562. The data should be sent to
the LTC3562 most significant bit (MSB) first.
The LTC3562 responds to only one 7-bit address which
has been factory programmed to 11001010. The eighth
bit of the address byte (R/W) must be 0 for the LTC3562
to recognize the address since it is a write-only device.
This effectively forces the address to be 8 bits long where
the least significant bit of the address is 0. If the correct
7-bit address is given but the R/W bit is 1, the LTC3562
will not respond.
Sub-Address Byte
The sub-address byte uses bits A7 through A4 to specify
the regulator(s) being programmed by that particular
three-byte sequence (refer to Table 2). A specific regulator
gets programmed if its corresponding sub-address bit is
high, whereas the regulator ignores the 3-byte sequence
if its sub-address bit is low. Note that multiple regulators
can be programmed by the same 3-byte sequence if more
than one of the sub-address bits are high. Bits A1 and A0
of the sub-address byte are used to program the operating
mode (Table 3). Bits A3 and A2 of the sub-address byte
are not used.
Data Byte
The data byte only affects the regulators that are specified
to be programmed by the sub-address byte. The MSB
of the data byte (B7) is used to enable or disable the
regulator(s) being programmed. A high B7 indicates an
enable command, whereas a low B7 indicates a shutdown
command.
3562fa
12
LTC3562
OPERATION
SUB-ADDRESS
ADDRESS
DATA BYTE
WR
1
1
0
0
1
0
1
0
SDA
1
1
0
0
1
0
1
0
SCL
1
2
3
4
5
6
7
8
A7
A6
A5
A4
A3
A2
A1
A0
B7
B6
B5
B4
B3
B2
B1
B0
ACK
A7
A6
A5
A4
A3
A2
A1
A0 ACK
7
6
5
4
3
2
1
0
ACK
9
1
2
3
4
5
6
7
8
1
2
3
4
5
6
7
8
9
START
STOP
9
3562 F03
Figure 3. Bit Assignments
SDA
tSU, STA
tSU, DAT
tLOW
tBUF
tSU, STO
tHD, STA
tHD, DAT
3562 F04
SCL
tHIGH
tHD, STA
START
CONDITION
tSP
REPEATED START
CONDITION
tf
tr
STOP
CONDITION
START
CONDITION
Figure 4. Timing Parameters
Table 1. Write Word Protocol Used by the LTC3562
1
7
1
1
8
1
8
1
1
S
Slave Address
WR
A
*Sub-Address
A
Data Byte
A
P**
S = Start Condition, WR = Write Bit = 0, A = Acknowledge, P = Stop Condition
* The sub-address uses only the first four most significant bits, A7, A6, A5, and A4, for sub-addressing. The two least significant bits, A1 and A0, are
used to program the regulator operating mode.
**Stop can be delayed until all of the data registers have been written.
Table 2. Sub-Address and Data Byte Mapping
SUB-ADDRESS BYTE
A7
A6
A5
A4
PROGRAM
R600A
PROGRAM
R400A
PROGRAM
R600B
PROGRAM
R400B
DATA BYTE
A3
A2
NOT USED
A1
A0
B7
ENABLE
REGULATOR
OPERATING REGULATOR
MODE
(SEE TABLE 3)
B6
B5
B4
B3
B2
B1
B0
DAC CODE
(See Tables 4, 5 and 6)
3562fa
13
LTC3562
OPERATION
If a Type-A regulator is being programmed, then bits B3
through B0 program the DAC that controls the regulator’s
feedback servo voltage. This 4-bit sequence programs the
feedback voltage from 425mV to 800mV in 25mV increments (Table 4). Bits B6 through B4 are not used when
programming a Type-A regulator.
will ignore this stop condition and will not respond until a
new start condition, correct address, new set of data and
stop condition are transmitted.
If a Type-B regulator is being programmed, then bits B6
through B0 program the DAC that controls the regulator’s
output voltage. This 7-bit sequence programs the output
voltage from 600mV to 3.775V in 25mV increments
(Tables 5 and 6).
Likewise, with only one exception, if the LTC3562 was
previously addressed and sent valid data but not updated
with a Stop, it will respond to any Stop that appears on
the bus, independent of the number of Repeat-Starts that
have occurred. If a Repeat-Start is given and the LTC3562
successfully acknowledges its address, it will not respond
to a Stop until all three bytes of the new data have been
received and acknowledged.
Bus Write Operation
I2C Examples
The master initiates communication with the LTC3562 with
a start condition and a 7-bit address followed by the write
bit R/W = 0. If the address matches that of the LTC3562,
the LTC3562 returns an Acknowledge. The master should
then deliver the sub-address byte for the regulator(s)
being programmed. Again the LTC3562 acknowledges
and then the data byte is delivered starting with the most
significant bit. The data byte and the two mode bits in the
sub-address byte are transferred to an internal holding
latch for each programmed regulator upon the return
of an Acknowledge. After the sub-address byte and data
byte have been transferred to the LTC3562, the master
may terminate the communication with a stop condition.
Alternatively, a repeat-start condition can be initiated by
the master and the entire sequence can be repeated, this
time accessing a different sub-address code to program
another regulator. Likewise, the master can also initiate a
Repeat-Start so that another chip on the I2C bus can be
addressed. This cycle can continue indefinitely and the
LTC3562’s regulators will remember the last input of valid
data that it received. Once all chips on the bus have been
addressed and sent valid data, a global stop condition can
be sent and the LTC3562 will update its regulators with
the data that it had received.
To program R600A in forced Burst Mode operation with
its feedback servo voltage set to 600mV:
In certain circumstances the data on the I2C bus may
become corrupted. In these cases the LTC3562 responds
appropriately by preserving only the last set of complete
data that it has received. For example, assume the LTC3562
has been successfully addressed and is receiving data
when a stop condition mistakenly occurs. The LTC3562
Sub-Address Byte – 1000XX10
Data Byte – 1XXX0111
To program R600B and R400B in LDO mode with their
output voltages set to 1.250V:
Sub-Address Byte – 0011XX01
Data Byte – 10011010
To put the entire chip in shutdown and disable all regulators:
Sub-Address Byte – 1111XXXX
Data Byte – 0XXXXXXX
Disabling the I2C Port
The I2C serial port can be disabled by grounding the DVCC
pin. In this mode, regulators R600A and R400A can only be
activated through the individual logic input pins RUN600A
and RUN400A. Disabling the I2C port also resets the feedback servo voltages to the default setting of 0.8V.
Note that if the I2C port gets disabled while a Type-A
regulator is enabled and its RUN pin is activated, the
regulator will remain enabled and its feedback voltage will
immediately be reset to the default setting of 0.8V. If the
I2C port gets disabled and the RUN pins are not activated,
then the regulators will immediately go into shutdown
mode. Since regulators R600B and R400B do not have
RUN pins, they immediately go into shutdown once the
I2C port gets disabled.
3562fa
14
LTC3562
OPERATION
Table 5. Type-B Regulator Base Output Voltage Programming
Table 3. Regulator Operating Modes
A1
A0
B6
B5
B4
B3
B2
TYPE-B REGULATOR
BASE OUTPUT VOLTAGE
0
0
0
0
0
0.600
0
0
0
0
1
0.700
0
0
0
1
0
0.800
0
0
0
1
1
0.900
0
0
1
0
0
1.000
0
0
1
0
1
1.100
0
0
1
1
0
1.200
REGULATOR MODE
0
0
Pulse Skip Mode
0
1
LDO Mode
1
0
Forced Burst Mode Operation
1
1
Burst Mode Operation
Table 4. Type-A Regulator Servo Voltage Programming
B3
B2
B1
B0
TYPE-A REGULATOR
SERVO (FEEDBACK) VOLTAGE
0
0
0
0
0.425
0
0
1
1
1
1.300
1
0
0
0
1.400
0
0
0
1
0.450
0
0
0
1
0
0.475
0
1
0
0
1
1.500
0
0
1
1
0.500
0
1
0
1
0
1.600
1
0
1
1
1.700
0
1
0
0
0.525
0
0
1
0
1
0.550
0
1
1
0
0
1.800
0
1
1
0
0.575
0
1
1
0
1
1.900
0
1
1
1
0.600
0
1
1
1
0
2.000
1
1
1
1
2.100
1
0
0
0
0.625
0
1
0
0
1
0.650
1
0
0
0
0
2.200
1
0
1
0
0.675
1
0
0
0
1
2.300
1
0
1
1
0.700
1
0
0
1
0
2.400
0
0
1
1
2.500
1
1
0
0
0.725
1
1
1
0
1
0.750
1
0
1
0
0
2.600
1
1
1
0
0.775
1
0
1
0
1
2.700
1
1
1
1
0.800
1
0
1
1
0
2.800
1
0
1
1
1
2.900
1
1
0
0
0
3.000
1
1
0
0
1
3.100
1
1
0
1
0
3.200
1
1
0
1
1
3.300
1
1
1
0
0
3.400
1
1
1
0
1
3.500
1
1
1
1
0
3.600
1
1
1
1
1
3.700
POR600A Pin
The POR600A pin is an open-drain output used to indicate
that regulator R600A has been enabled and has reached
its final voltage. POR600A remains low impedance until
regulator R600A reaches 92% of its regulation value. A
230ms delay is included to allow a system microcontroller
ample time to reset itself. POR600A may be used as a
power on reset to the microprocessor powered by regulator R600A or may be used to enable regulator R400A for
supply sequencing. POR600A is an open drain output and
requires a pull-up resistor to the output voltage of regulator
R600A or another appropriate power source.
Table 6. Type-B Regulator Incremental Output Voltage Programming
B1
B0
TYPE-B REGULATOR INCREMENTAL OUTPUT VOLTAGE
0
0
+0.000
0
1
+0.025
1
0
+0.050
1
1
+0.075
3562fa
15
LTC3562
APPLICATIONS INFORMATION
Inductor Selection
Many different sizes and shapes of inductors are available from numerous manufacturers. Choosing the right
inductor from such a large selection of devices can be
overwhelming, but following a few basic guidelines will
make the selection process much simpler.
The step-down converters are designed to work with inductors in the range of 2.2μH to 10μH. For most applications a
4.7μH inductor is suggested for the lower power switching
regulators R400A and R400B and 3.3μH is recommended
for the more powerful switching regulators R600A and
R600B. Larger value inductors reduce ripple current which
improves output ripple voltage. Lower value inductors
result in higher ripple current and improved transient response time, but will reduce the available output current.
To maximize efficiency, choose an inductor with a low DC
resistance. For a 1.2V output, efficiency is reduced about
2% for 100mΩ series resist-ance at 400mA load current,
and about 2% for 300mΩ series resistance at 100mA load
current. Choose an inductor with a DC current rating at
least 1.5 times larger than the maximum load current to
ensure that the inductor does not saturate during normal
operation. If output short circuit is a possible condition,
the inductor should be rated to handle the maximum peak
current specified for the step-down converters.
Different core materials and shapes will change the size/current and price/current relationship of an inductor. Toroid
or shielded pot cores in ferrite or Permalloy™ materials
are small and do not radiate much energy, but generally
cost more than powdered iron core inductors with similar
electrical characteristics. Inductors that are very thin or
have a very small volume typically have much higher core
and DCR losses, and will not give the best efficiency. The
choice of which style inductor to use often depends more
on the price versus size, performance, and any radiated
EMI requirements than on what the LTC3562 requires to
operate.
The inductor value also has an effect on Burst Mode and
forced Burst Mode operations. Lower inductor values will
cause the Burst Mode and forced Burst Mode switching
frequencies to increase.
Table 7 shows several inductors that work well with the
LTC3562’s general purpose regulators. These inductors offer a good compromise in current rating, DCR and physical
size. Consult each manufacturer for detailed information
on their entire selection of inductors.
Table 7. Recommended Inductors
INDUCTOR L
TYPE
(μH)
MAX
IDC
(A)
MAX
DCR
(Ω)
SIZE
(mm)
(L × W × H)
4.7
3.3
4.7
3.3
4.7
3.3
4.7
3.3
1.07
1.20
0.79
0.90
1.15
1.37
1.25
1.45
0.1
0.07
0.24
0.20
0.13*
0.105*
0.072*
0.052*
3.8 × 3.8 × 1.8
3.8 × 3.8 × 1.8
3.6 × 3.6 × 1.2
3.6 × 3.6 × 1.2
3.0 × 2.8 × 1.2
3.0 × 2.8 × 1.2
3.0 × 2.8 × 1.8
3.0 × 2.8 × 1.8
Toko
www.toko.com
CDRH3D16 4.7
3.3
CDRH2D11 4.7
3.3
CLS4D09
4.7
0.9
1.1
0.5
0.6
0.75
0.11
0.085
0.17
0.123
0.19
4 × 4 × 1.8
4 × 4 × 1.8
3.2 × 3.2 × 1.2
3.2 × 3.2 × 1.2
4.9 × 4.9 × 1
Sumida
www.sumida.com
4.7
3.3
4.7
3.3
4.7
3.3
4.7
3.3
1.3
1.59
0.8
0.97
1.29
1.42
1.08
1.31
0.162
0.113
0.246
0.165
0.117*
0.104*
0.153*
0.108*
3.1 × 3.1 × 1.8
Cooper
3.1 × 3.1 × 1.8 www.cooperet.com
3.1 × 3.1 × 1.2
3.1 × 3.1 × 1.2
5.2 × 5.2 × 1.2
5.2 × 5.2 × 1.2
5.2 × 5.2 × 1.0
5.2 × 5.2 × 1.0
4.7
3.3
1.1
1.3
0.2
0.13
3.0 × 3.0 × 1.5
Coil Craft
3.0 × 3.0 × 1.5 www.coilcraft.com
DB318C
D312C
DE2812C
DE2818C
SD3118
SD3112
SD12
SD10
LPS3015
MANUFACTURER
* Typical DCR
Input/Output Capacitor Selection
Low ESR (equivalent series resistance) ceramic capacitors
should be used at the switching regulator outputs as well
as the input supply. Only X5R or X7R ceramic capacitors
should be used because they retain their capacitance
over wider voltage and temperature ranges than other
ceramic types. A 10μF output capacitor is sufficient for
most applications. For good transient response and stability the output capacitor should retain at least 4μF of
capacitance over operating temperature and bias voltage.
The input supply should be bypassed with a 10μF capacitor, or greater. Consult with capacitor manufacturers for
detailed information on their selection and specifications
of ceramic capacitors. Many manufacturers now offer
3562fa
16
LTC3562
APPLICATIONS INFORMATION
very thin (<1mm tall) ceramic capacitors ideal for use in
height-restricted designs. Table 8 shows a list of several
ceramic capacitor manufacturers.
Table 8. Recommended Ceramic Capacitor Manufacturers
AVX
www.avxcorp.com
Murata
www.murata.com
Taiyo Yuden
www.t-yuden.com
Vishay Siliconix
www.vishay.com
TDK
www.tdk.com
Printed Circuit Board Layout Considerations
To deliver maximum current under all conditions, it is critical
that the exposed metal pad on the backside of the LTC3562
package be soldered to the PC board ground. Correctly
soldered to a 2500mm2 double-sided 1oz. copper board,
the LTC3562 has a thermal resistance of less than 68°C/W.
Failure to make thermal contact between the exposed pad
on the backside of the package and the copper board will
result in higher thermal resistances.
Furthermore, due to its high frequency switching circuitry,
it is imperative that the input capacitors, inductors, and
output capacitors be as close to the LTC3562 as possible
and that there be an unbroken ground plane under the
LTC3562 and all of its external high frequency components. High frequency currents on the LTC3562 tend to
find their way along the ground plane in a myriad of paths
ranging from directly back to a mirror path beneath the
incident path on the top of the board. If there are slits or
cuts in the ground plane due to other traces on that layer,
the current will be forced to go around the slits. If high
frequency currents are not allowed to flow back through
their natural least-area path, excessive voltage will build
up and radiated emissions will occur. There should be a
group of vias directly under the grounded backside of the
package leading directly down to an internal ground plane.
To minimize parasitic inductance, the ground plane should
be on the second layer of the PC board.
3562 F05
Figure 5. High Frequency Ground Currents Follow Their Incident Path.
Slices in the Ground Cause High Voltage and Increased Emissions.
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17
LTC3562
TYPICAL APPLICATION
Quad Step-Down Converter with Push Button Control and Power Sequencing
100k
C5
10μF
Li-Ion BATTERY
3.4V TO 4.2V
SDA
VIN
VOUT 600B
3.3V
600mA
VOUT 400B
1.2V
400mA
L3
3.3μH
SCL
DVCC
LTC3562
SW600B
C3
10μF
OUT600B
R5
100k
R1
634k
FB600A
L4
4.7μH
C4
10μF
POR600A
SW600A
L1
3.3μH
RUN600A
VOUT 600A
1.8V
600mA
C6
10pF
C1
10μF
POR SCL SDA
VCC CORE
VCC I/O
MICROPROCESSOR
SW400B
OUT400B
R2
499k
RUN400A
VOUT 400A
2.5V
400mA
L2
4.7μH
SW400A
FB400A
PGND AGND
3562 TA02
R3
1070k
C7
10pF
C2
10μF
R4
499k
3562fa
18
LTC3562
PACKAGE DESCRIPTION
UD Package
20-Lead Plastic QFN (3mm × 3mm)
(Reference LTC DWG # 05-08-1720 Rev Ø)
0.70 ±0.05
3.50 ± 0.05
(4 SIDES)
1.65 ± 0.05
2.10 ± 0.05
PACKAGE
OUTLINE
0.20 ±0.05
0.40 BSC
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED
3.00 ± 0.10
(4 SIDES)
BOTTOM VIEW—EXPOSED PAD
R = 0.115
TYP
0.75 ± 0.05
R = 0.05
TYP
PIN 1
TOP MARK
(NOTE 6)
PIN 1 NOTCH
R = 0.20 TYP
OR 0.25 × 45°
CHAMFER
19 20
0.40 ± 0.10
1
2
1.65 ± 0.10
(4-SIDES)
(UD20) QFN 0306 REV A
0.200 REF
0.00 – 0.05
NOTE:
1. DRAWING IS NOT A JEDEC PACKAGE OUTLINE
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION
ON THE TOP AND BOTTOM OF PACKAGE
0.20 ± 0.05
0.40 BSC
3562fa
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 representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
19
LTC3562
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LTC3406/
LTC3406B
600mA IOUT, 1.5MHz, Synchronous Step-Down
DC/DC Converter
96% Efficiency, VIN(MIN) = 2.5V, VIN(MAX) = 5.5V, VOUT(MIN) = 0.6V, IQ = 20μA,
ISD < 1μA, ThinSOT™ Package
LTC3407/
LTC3407-2
Dual 600mA/800mA IOUT, 1.5MHz/2.25MHz,
Synchronous Step-Down DC/DC Converter
95% Efficiency, VIN(MIN) = 2.5V, VIN(MAX) = 5.5V, VOUT(MIN) = 0.6V, IQ = 40μA,
ISD < 1μA, MS10E and DFN Packages
LTC3410/
LTC3410B
300mA IOUT, 2.25MHz, Synchronous Step-Down
DC/DC Converter
95% Efficiency, VIN(MIN) = 2.5V, VIN(MAX) = 5.5V, VOUT(MIN) = 0.8V, IQ = 26μA,
ISD < 1μA, SC70 Package
LTC3531/LTC3531-3/ 200mA IOUT, 1.5MHz, Synchronous Buck-Boost
DC/DC Converter
LTC3531-3.3
95% Efficiency, VIN(MIN) = 1.8V, VIN(MAX) = 5.5V, VOUT(MIN): 2V to 5V,
IQ = 16μA, ISD < 1μA, ThinSOT and DFN Packages
LTC3532
500mA IOUT, 2MHz, Synchronous Buck-Boost
DC/DC Converter
95% Efficiency, VIN(MIN) = 2.4V, VIN(MAX) = 5.5V, VOUT(MIN): 2.4V to 5.25V,
IQ = 35μA, ISD < 1μA, MS10 and DFN Packages
LTC3542
500mA IOUT, 2.25MHz, Synchronous Step-Down
DC/DC Converter
95% Efficiency, VIN(MIN) = 2.5V, VIN(MAX) = 5.5V, VOUT(MIN) = 0.6V, IQ = 26μA,
ISD < 1μA, 2mm × 2mm DFN Package
LTC3544/LTC3544B
Quad 300mA and 2 × 200mA and 100mA, 2.25MHz, 95% Efficiency, VIN(MIN) = 2.5V, VIN(MAX) = 5.5V, VOUT(MIN) = 0.8V, IQ = 70μA,
ISD < 1μA, 3mm × 3mm QFN Package
Synchronous Step-Down DC/DC Converter
LTC3547/
LTC3547B
Dual 300mA, 2.25MHz, Synchronous Step-Down
DC/DC Converter
LTC3548/LTC3548-1/ Dual 400mA and 800mA IOUT, 2.25MHz,
Synchronous Step-Down DC/DC Converter
LTC3548-2
LTC3560
800mA IOUT, 2.25MHz, Synchronous Step-Down
DC/DC Converter
96% Efficiency, VIN(MIN) = 2.5V, VIN(MAX) = 5.5V, VOUT(MIN) = 0.6V, IQ = 40μA,
ISD < 1μA, 2mm × 3mm DFN Package
95% Efficiency, VIN(MIN) = 2.5V, VIN(MAX) = 5.5V, VOUT(MIN) = 0.6V, IQ = 40μA,
ISD < 1μA, MS10E and DFN Packages
95% Efficiency, VIN(MIN) = 2.5V, VIN(MAX) = 5.5V, VOUT(MIN) = 0.6V, IQ = 16μA,
ISD < 1μA, ThinSOT Package
ThinSOT is a trademark of Linear Technology Corporation
3562fa
20 Linear Technology Corporation
LT 1207 REV A • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com
© LINEAR TECHNOLOGY CORPORATION 2007
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