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LTC3523EUD-2#PBF

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P16
LTC3523/LTC3523-2
4
3523fb
TYPICAL PERFORMANCE CHARACTERISTICS
Normalized FBx Reference vs
Temperature
Inrush Current Control for the
Step-Up Converter
Inrush Current Control for the
Step-Down Converter
Load Transient Response Step-Up
Load Transient Response
Step-Down
Current Limit vs Temperature
R
DS(ON)
vs Input Voltage for the
Step-Down Converter
Normalized Oscillator Frequency
vs Temperature
TEMPERATURE (°C)
–45 –25 –5
NORMALIZED FBx VOLTAGE (V)
1.00000
1.00125
75
3523 G01
0.99875
0.99500
0.99750
0.99625
15 35 55
TEMPERATURE (°C)
–45 –25 –5
NORMALIZED FREQUENCY (Hz)
1.00
1.05
75
3523 G02
0.95
15 35 55
V
OUT_BCK
1V/DIV
I
L_BCK
200mA/DIV
200μs/DIV
3523 G04
V
OUT
= 1.2V
V
IN
= 2.4V
C
OUT
= 10μF
L1 = 4.7μH
SHDN2
2V/DIV
OUTPUT
RIPPLE
20mV/DIV
LOAD
CURRENT
20mA/DIV
500μs/DIV
3523 G05
V
OUT
= 3.3V
V
IN
= 2.4V
C
OUT
= 10μF
L1 = 4.7μH
20mA TO 70mA STEP
OUTPUT
RIPPLE
20mV/DIV
LOAD
CURRENT
20mA/DIV
500μs/DIV
3523 G06
V
OUT
= 1.2V
V
IN
= 2.4V
C
OUT
= 47μF
L1 = 4.7μH
C
F
= 68pF
10mA TO 30mA STEP
R
DS(ON)
vs Output Voltage for the
Step-Up Converter
TEMPERATURE (°C)
–45
CURRENT LIMIT (A)
0.8
1.0
1.2
35 75
3523 G07
0.6
0.4
–25 –5 15
55
0.2
0
BOOST CURRENT
LIMIT
BUCK CURRENT
LIMIT
INPUT VOLTAGE (V)
1
R
DS(ON)
(Ω)
0.40
0.60
5
3523 G08
0.20
0
2
3
4
1.5
2.5
3.5
4.5
0.80
0.30
0.50
0.10
0.70
PMOS
NMOS
OUTPUT VOLTAGE (V)
1
0
R
DS(0N)
(Ω)
0.05
0.15
0.20
0.25
0.50
0.35
2
3
3.5
3532 G09
0.10
0.40
0.45
0.30
1.5 2.5
4
4.5
5
PMOS
NMOS
(T
A
= 25°C unless otherwise noted)
V
OUT_BST
2V/DIV
I
L_BST
200mA/DIV
SHDN1
2V/DIV
200μs/DIV
3523 G03
V
OUT
= 3.3V
V
IN
= 2.4V
C
OUT
= 10μF
L1 = 4.7μH
LTC3523/LTC3523-2
5
3523fb
Normalized R
DS(ON)
vs
Temperature
Step-Up No-Load Input Current
vs V
IN
PIN FUNCTIONS
FB1 (Pin 1): Step-Up Converter Feedback Input to the Er-
ror Amplifi er. Connect resistor divider tap to this pin. The
output voltage can be adjusted from 1.8V to 5.25V by:
V
OUT(STEP-UP)
=+
⎛
⎝
⎜
⎞
⎠
⎟
12 1
1
2
.•V
R
R
See Block Diagram.
V
IN1
(Pin 2): Step-Up Converter Power Voltage Input. This
pin can be connected to a different supply than V
IN2
. This
pin must be connected to a valid supply voltage.
PGOOD1 (Pin 3): Step-Up Converter Power Good Com-
parator Output. This open-drain output is pulled low when
V
FB1
< –9% of its regulation voltage.
V
OUT
(Pin 4): Step-Up Converter Output Voltage Sense Input
and Drain of the Internal Synchronous Rectifi er MOSFET.
Driver bias is derived from V
OUT
. PCB trace length from
V
OUT
to the output fi lter capacitor(s) should be as short
and wide as possible.
Mode Transition Response
TEMPERATURE (°C)
–45
NORMALIZED R
DS(ON)
(Ω)
1.2
15
3523 G10
0.9
0.7
–25 –5 35
0.6
0.5
1.3
1.1
1.0
0.8
55 75
PMOS
NMOS
INPUT VOLTAGE (V)
1.5
0
INPUT CURRENT (μA)
50
150
200
250
500
350
2.5
3.5
4
3523 G11
100
400
450
300
2
3
4.5
5
V
OUT
= 5V
V
OUT
= 3.3V
V
OUT
= 2.8V
V
OUT_BST
50mV/DIV
V
OUT_BCK
20mV/DIV
MODE
2V/DIV
200μs/DIV
3523 G12
V
OUT1
= 3.3V
V
OUT2
= 1.2V
V
IN
= 2.4V
I
OUT1
= 20mA
I
OUT2
= 25mA
C
OUT1
= C
OUT2
= 10μF
L1 = L2 = 4.7μH
Maximum I
OUT
vs V
IN
for the
Step-Up Converter
Maximum I
OUT
vs V
IN
for the
Step-Down Converter
INPUT VOLTAGE (V)
1
0
MAXIMUM OUTPUT CURRENT (mA)
50
150
200
250
500
350
2
3
3523 G13
100
400
450
300
4
5
V
OUT
= 2.5V
V
OUT
= 3.3V
V
OUT
= 5V
INPUT VOLTAGE (V)
1
MAXIMUM OUTPUT CURRENT (mA)
250
300
350
5
3523 G14
200
150
0
2
3
4
1.5
2.5
3.5
4.5
100
50
450
400
V
OUT
= 2.5V
V
OUT
= 1.8V
V
OUT
= 1.2V
TYPICAL PERFORMANCE CHARACTERISTICS
(T
A
= 25°C unless otherwise noted)
LTC3523/LTC3523-2
6
3523fb
PIN FUNCTIONS
SW1 (Pin 5): Step-Up Converter Switch Pin. Connect the
inductor between SW1 and V
IN1
. Keep these PCB trace
lengths as short and wide as possible to reduce EMI and
voltage overshoot. If the inductor current falls to zero or
SHDN1 is low, an internal 150Ω anti-ringing resistor is
connected from SW1 to V
IN1
to minimize EMI.
GND1 (Pin 6): Step-Up Converter Power Ground. Connect
this pin to the ground plane.
GND2 (Pin 7): Step-Down Converter Power Ground. Con-
nect this pin to the ground plane.
SW2 (Pin 8): Step-Down Converter Switch Pin. Connect
one end of the inductor to SW2. Keep these PCB trace
lengths as short and wide as possible to reduce EMI and
voltage overshoot.
V
IN2
(Pin 9): Step-Down Converter Power Voltage Input.
This pin can be connected to a different supply than V
IN1
.
This pin must be connected to a valid supply voltage.
MODE (Pin 10): Step-Up and Step-Down Converter Mode
Selection Pin. Do not leave this pin fl oating.
• MODE = Low: PWM mode
• MODE = High: Automatic Burst Mode operation
PGOOD2 (Pin 11): Step-Down Converter Power Good
Comparator Output. This open-drain output is pulled low
when V
FB2
< –9% of its regulation voltage.
FB2 (Pin 12): Step-Down Converter Feedback Input to the
Error amplifi er. Connect resistor divider tap to this pin. The
output voltage can be adjusted from 0.6V to 5.5V by:
V
OUT(STEP-DOWN)
=+
⎛
⎝
⎜
⎞
⎠
⎟
06 1
3
4
.•V
R
R
See Block Diagram.
If large feedback resistors, above 500k are used, then it
will be necessary to use a lead capacitor connected to the
output voltage and FB2.
SHDN2 (Pin 13): Step-Down Converter Logic Controlled
Shutdown Input. Do not leave this pin fl oating.
• SHDN2 = High: Normal free-running operation,
1.2MHz/2.4MHz typical operating frequency.
• SHDN2 = Low: Shutdown, quiescent current < 1μA.
This pin cannot exceed the voltage on V
IN2
.
GND3 (Pin 14): Analog Ground. The feedback voltage
dividers for each converter must be returned to GND3
for best performance.
Note: When laying out your PCB provide a short direct
path between GND1 and the (–) side of the step-up output
capacitor(s) and GND2 and the step-down output capaci-
tor.These pins are not connected together internally.
V
BAT
(Pin 15): Analog Voltage Input. Connect this pin to
the higher of V
IN1
or V
IN2
.
SHDN1 (Pin 16): Step-Up Converter Logic Controlled
Shutdown Input.
• SHDN1 = High: Normal free-running operation,
1.2MHz/2.4MHz typical operating frequency.
• SHDN1 = Low: Shutdown, quiescent current < 1μA.
This pin cannot exceed the voltage on V
IN1
.
Exposed Pad (Pin 17): Die attach pad must be soldered
to PCB ground for electrical contact and optimum thermal
performance.
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P16

LTC3523EUD-2#PBF

Mfr. #:
Buy LTC3523EUD-2#PBF
Manufacturer:
Analog Devices / Linear Technology
Description:
Switching Voltage Regulators Sync 600mA Boost & 400mA Buck DC/DC Conv
Lifecycle:
New from this manufacturer.
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