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Linear Technology Electronic Components Datasheet

LTC3445EUF Datasheet

I2C Controllable Buck Regulator

No Preview Available !

LTC3445
I2C Controllable
Buck Regulator with Two LDOs
in a 4mm × 4mm QFN
FEATURES
Buck Regulator
High Efficiency: Up to 93%
600mA Output Current (VCC1 = 3V, VOUT = 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 VCC BATT
I2C
Standard (100kHz) or Fast Mode (400kHz)
24-Lead (4mm × 4mm) QFN Package
U
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.
I2C is a trademark of Philips Electronics N.V.
Protected by U.S. Patents, including 5481178, 6580258, 6304066, 6127815, 6498466,
6611131, Spread Spectrum patent pending.
DESCRIPTIO
The LTC®3445 contains a high efficiency monolithic syn-
chronous current mode buck regulator, two LDO regula-
tors, a PowerPathTM controller and an I2CTM 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 I2C 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. VBACKUP 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.
TYPICAL APPLICATIO
VCC
4.7µF
CER
3V
COIN
+
VBACKUP
CELL
PWR_EN
I2C BUS
VCC
20k
nVCC_FAULT
VCC1 OR GND
VCC1 OR GND
VCC1 VCC2 VCC1
VTRACK
VBACKUP
BATTFAULT
VCC BATT
RUN
SW
SDA
FB
LTC3445
SCL
LDO1
ADD7
ADD6
PGOOD
LDO1FB
LDO2
GND LDO2FB
VBACKUP
2.2µH
705k
20k
4.7µF
CER
4.7µF
CER
nBATT_FAULT
3VTYP
0.85V
TO 1.55V
1.3V
604k
10µF
CER
503k
604k
1.1V
10µF
CER
3445 TA01
Efficiency and Power Loss
vs Load Current, VCC1 = 3.6V
100
90
80
70
60
50
40
30
20
10
0
0.1
EFFICIENCY
DAC MAX
DAC MIN
1000
100
DAC MAX
10
DAC MIN
POWER LOSS
1.0
1
10
100
LOAD CURRENT (mA)
0.1
1000
3445 TA01b
3445fa
1


Linear Technology Electronic Components Datasheet

LTC3445EUF Datasheet

I2C Controllable Buck Regulator

No Preview Available !

LTC3445
ABSOLUTE AXI U RATI GS
(Note 1)
VCC1, VCC2, SDA, SCL Voltages .................. – 0.3V to 6V
RUN, VTRACK, VBACKUP, PGOOD, ADD7,
ADD6, FB, VCC BATT,
BATTFAULT Voltages .............................. – 0.3V to VCC1
SW Voltage ................................ – 0.3V to (VCC1 + 0.3V)
LDO1FB, LDO2FB Voltages ..................... – 0.3V to VCC2
LDO1, LDO2 Voltages ................ – 0.3V to (VCC2 + 0.3V)
LDO1, LDO2 Source Current ............................... 50mA
VCC BATT Source Current ...................................... 8mA
P-Channel Switch Source Current (DC) ............. 800mA
N-Channel Switch Sink Current (DC) ................. 800mA
Peak SW Sink and Source Current ........................ 1.3A
LDO1, LDO2, VCC BATT Output Short-Circuit
Duration .......................................................... Indefinite
Operating Temperature Range (Note 2) ...–40°C to 85°C
Junction Temperature (Note 3) ............................ 125°C
Storage Temperature Range ................. –65°C to 125°C
UW U
PACKAGE/ORDER I FOR ATIO
TOP VIEW
24 23 22 21 20 19
VTRACK 1
VBACKUP 2
VCC1 3
PGOOD 4
ADD7 5
SDA 6
18 VCC BATT
17 FB
16 NC
25
15 RUN
14 SW
13 NC
7 8 9 10 11 12
UF PACKAGE
24-LEAD (4mm × 4mm) PLASTIC QFN
TJMAX = 125°C, θJA = 37°C/W, θJC = 2.6°C/W
EXPOSED PAD (PIN 25) IS GND, MUST BE SOLDERED TO PCB
ORDER PART NUMBER UF PART MARKING
LTC3445EUF
3445
Order Options Tape and Reel: Add #TR
Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking: http://www.linear.com/leadfree/
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS The denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC1 = VCC2 = 3.6V, unless otherwise noted.
SYMBOL PARAMETER
CONDITIONS
MIN TYP MAX
VCC1, VCC2 Input Voltage Range
RUN
Run Threshold
2.5
5.5
0.3
1
1.5
PGOOD Reports Undervoltage of any Regulator
PGOOD = 0.4V
3
IS
DC Bias Current (Shutdown)
RUN = 0
DC Bias Current (Buck, LDO1, LDO2 Disabled) RUN = VCC1
27
50
105 150
Buck Regulator
RFB
Feedback Resistance
340
VOUT(MIN) Regulated Output Voltage
IOUT = 100mA, Burst Mode Operation
Disabled
0.824 0.850 0.875
VOUT(MAX) Regulated Output Voltage
IOUT = 100mA, Burst Mode Operation
Disabled
1.504 1.55 1.597
VOUT(STEP) Output Voltage Step Size (0 to 48)
Output Voltage Slew Rate = 00
IOUT = 100mA
IOUT = 100mA, VOUT = 0.85V to 1.55V
13.1 14.7 16.1
11.3
Output Voltage Slew Rate = 01
IOUT = 100mA, VOUT = 0.85V to 1.55V
7.5
Output Voltage Slew Rate = 10
IOUT = 100mA, VOUT = 0.85V to 1.55V
3.8
Output Voltage Slew Rate = 11
IPK
Peak Inductor Current
IOUT = 100mA, VOUT = 0.85V to 1.55V
VCC1 = 3V, VFB = 0.5V or VOUT = 90%,
Duty Cycle < 35%
0.9
0.75
1
1.25
VLOADREG Output Voltage Load Regulation
0.5
UNITS
V
V
mA
µA
µA
k
V
V
mV
mV/µs
mV/µs
mV/µs
mV/µs
A
%
3445fa
2


Part Number LTC3445EUF
Description I2C Controllable Buck Regulator
Maker Linear
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