LTC4055

Part No.:
LTC4055
Download:
Download
Description:
I2C Controllable Buck Regulator with Two LDOs in a 4mm ?4mm QFN
File Size:
466 K
Page:
24 Pages
Logo:
Maker:
LINER [ LINEAR TECHNOLOGY ]
PCB Prototype

July 16, 2018:

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M27C202-150N1TR

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M27C4002-20XN1X

M27C405-90K6TR

M27V402-180K4TR

M295V100-B90XM6R

PCB Datasheet:1PCB Datasheet:1PCB Datasheet:1
LTC3445
I
2
C Controllable
Buck Regulator with Two LDOs
in a 4mm
×
4mm QFN
FEATURES
Buck Regulator
High Efficiency: Up to 93%
600mA Output Current (V
CC1
= 3V, V
OUT
= 1.3V)
Programmable Output Voltage: 0.85V to 1.55V
2.5V to 5.5V Input Voltage Range
1.5MHz Constant Frequency or Spread Spectrum
Option
Soft-Start
LDOs
Two LDO Regulators: 0.3V Dropout at 50mA
PowerPath Controller
Dynamically Regulates V
CC
BATT
I
2
C
Standard (100kHz) or Fast Mode (400kHz)
24-Lead (4mm
×
4mm) QFN Package
DESCRIPTIO
The LTC
®
3445 contains a high efficiency monolithic syn-
chronous current mode buck regulator, two LDO regula-
tors, a PowerPath
TM
controller and an I
2
C
TM
interface.
The buck regulator has a 6-bit programmable output range
of 0.85V to 1.55V. Also, the buck regulator uses either a
constant (1.5MHz) or a spread spectrum switching fre-
quency. Using the spread spectrum option allows for a
lower noise regulated output as well as low noise at the
input. In addition, the regulated output voltage slew rate is
programmable via the I
2
C interface.
The LTC3445 contains two LDO voltage regulators. The
regulator output voltages are externally resistor program-
mable. Each LDO is capable of delivering up to 50mA.
The LTC3445 contains control circuitry (PowerPath) for
automatic back-up battery selection. V
BACKUP
is typically
a coin cell.
Typical supply current during operation is only 360µA and
drops to 27µA in shutdown. The 2.5V to 5.5V input
voltage range makes the LTC3445 ideal for single Li-Ion
battery-powered applications. Automatic Burst Mode
®
operation increases efficiency at light loads, further ex-
tending battery life.
APPLICATIO S
Intel’s Microprocessor Supply (PXA27X)
Portable Instruments
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark of Linear Technology Corporation.
PowerPath is a trademark of Linear Technology Corporation.
I
2
C is a trademark of Philips Electronics N.V.
Protected by U.S. Patents, including 5481178, 6580258, 6304066, 6127815, 6498466,
6611131, Spread Spectrum patent pending.
TYPICAL APPLICATIO
V
CC
4.7µF
CER
V
BACKUP
V
CC1
V
TRACK
V
BACKUP
V
BACKUP
V
CC2
V
CC1
V
CC
BATT
2.2µH
PWR_EN
I
2
C BUS
V
CC
20k
nV
CC
_FAULT
V
CC1
OR GND
V
CC1
OR GND
ADD7
ADD6
PGOOD
GND
LDO1FB
LDO2
503k
LDO2FB
3445 TA01
20k
nBATT_FAULT
4.7µF
CER
4.7µF
CER
705k
604k
10µF
CER
1.1V
604k
10µF
CER
3V
TYP
BATTFAULT
3V
COIN
CELL
+
RUN
SDA
SCL
LTC3445
SW
FB
LDO1
EFFICIENCY (%)
0.85V
TO 1.55V
1.3V
U
Efficiency and Power Loss
vs Load Current, V
CC1
= 3.6V
100
90
80
70
60
50
40
30
20
10
0
0.1
1
10
100
LOAD CURRENT (mA)
0.1
1000
3445 TA01b
U
U
1000
EFFICIENCY
DAC MAX
DAC MIN
100
POWER LOSS (mW)
DAC MAX
10
DAC MIN
1.0
POWER LOSS
3445fa
1