, LTC and LT are registered trademarks of Linear Technology Corporation.
?/DIV>
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 360礎 and
drops to 27礎 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
?/DIV>
operation increases efficiency at light loads, further ex-
tending battery life.
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.
FEATURES
DESCRIPTIO
APPLICATIO S
TYPICAL APPLICATIO
+
2.2礖
705k
604k
4.7礔
CER
4.7礔
CER
10礔
CER
1.3V
0.85V
TO 1.55V
3V
TYP
V
CC2
GND
LTC3445
V
CC1
nBATT_FAULT
V
CC1
BATTFAULT
4.7礔
CER
V
CC
BATT
V
TRACK
3V
COIN
CELL
V
BACKUP
LDO1
LDO1FB
LDO2
LDO2FB
SW
FB
RUN
SDA
I
2
C BUS
PWR_EN
V
CC1
OR GND
V
CC1
OR GND
SCL
ADD7
ADD6
PGOOD
V
CC
nV
CC
_FAULT
V
CC
20k
3445 TA01
503k   604k
10礔
CER
1.1V
V
BACKUP
20k
V
BACKUP
Efficiency and Power Loss
vs Load Current, V
CC1
= 3.6V
LOAD CURRENT (mA)
30
90
100
20
10
80
50
70
60
40
0.1
10    100   1000
3445 TA01b
0
1
DAC MAX
DAC MIN
DAC MIN
DAC MAX
100
1000
10
1.0
0.1
EFFICIENCY
POWER LOSS