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Linear Technology Electronic Components Datasheet

LTC1878 Datasheet

High Efficiency Monolithic Synchronous Step-Down Regulator

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LTC1878 pdf
LTC1878
High Efficiency
Monolithic Synchronous
Step-Down Regulator
FEATURES
s High Efficiency: Up to 95%
s Very Low Quiescent Current: Only 10µA
During Operation
s 600mA Output Current at VIN = 3.3V
s 2.65V to 6V Input Voltage Range
s 550kHz Constant Frequency Operation
s Synchronizable from 400kHz to 700kHz
s Selectable Burst ModeTM Operation or
Pulse Skipping Mode
s No Schottky Diode Required
s Low Dropout Operation: 100% Duty Cycle
s 0.8V Reference Allows Low Output Voltages
s Shutdown Mode Draws < 1µA Supply Current
s ±2% Output Voltage Accuracy
s Current Mode Control for Excellent Line and
Load Transient Response
s Overcurrent and Overtemperature Protected
s Available in 8-Lead MSOP Package
U
APPLICATIO S
s Cellular Telephones
s Wireless Modems
s Personal Information Appliances
s Portable Instruments
s Distributed Power Systems
s Battery-Powered Equipment
DESCRIPTIO
The LTC®1878 is a high efficiency monolithic synchro-
nous buck regulator using a constant frequency, current
mode architecture. Supply current during operation is
only 10µA and drops to < 1µA in shutdown. The 2.65V to
6V input voltage range makes the LTC1878 ideally suited
for single Li-Ion battery-powered applications. 100% duty
cycle provides low dropout operation, extending battery
life in portable systems.
Switching frequency is internally set at 550kHz, allowing
the use of small surface mount inductors and capacitors.
For noise sensitive applications the LTC1878 can be
externally synchronized from 400kHz to 700kHz. Burst
Mode operation is inhibited during synchronization or
when the SYNC/MODE pin is pulled low, preventing low
frequency ripple from interfering with audio circuitry.
The internal synchronous switch increases efficiency and
eliminates the need for an external Schottky diode. Low
output voltages are easily supported with the 0.8V feed-
back reference voltage. The LTC1878 is available in a
space saving 8-lead MSOP package.
For higher input voltage (11V abs max) applications, refer
to the LTC1877 data sheet.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a trademark of Linear Technology Corporation.
TYPICAL APPLICATIO
High Efficiency Step-Down Converter
VIN
2.65V
TO 6V 22µF**
CER
220pF
7
SYNC
5
SW
6
VIN
1 LTC1878
RUN
23
ITH GND VFB
4
10µH*
20pF
887k
280k
*TOKO D62CB A920CY-100M
**TAIYO-YUDEN CERAMIC JMK325BJ226MM
***SANYO POSCAP 6TPA47M
VOUT CONNECTED TO VIN FOR 2.65V < VIN < 3.3V
VOUT
3.3V
+
47µF***
1878 TA01
Efficiency vs Output Load Current
100
95 VIN = 3.6V
90
VIN = 4.2V
85
VIN = 6V
80
75
70
0.1
Burst Mode OPERATION
VOUT = 3.3V
L = 10µH
1 10 100
OUTPUT CURRENT (mA)
1000
1878 TA02
1


Linear Technology Electronic Components Datasheet

LTC1878 Datasheet

High Efficiency Monolithic Synchronous Step-Down Regulator

No Preview Available !

LTC1878 pdf
LTC1878
ABSOLUTE AXI U RATI GS
(Note 1)
Input Supply Voltage (VIN)...........................– 0.3V to 7V
ITH, PLL LPF Voltage ................................– 0.3V to 2.7V
RUN, VFB Voltages ...................................... – 0.3V to VIN
SYNC/MODE Voltage .................................. – 0.3V to VIN
SW Voltage ................................... – 0.3V to (VIN + 0.3V)
P-Channel MOSFET Source Current (DC) ........... 800mA
N-Channel MOSFET Sink Current (DC) ............... 800mA
Peak SW Sink and Source Current ........................ 1.5A
Operating Ambient Temperature Range
(Note 2) .................................................. – 40°C to 85°C
Junction Temperature (Note 3) ............................ 125°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
UW U
PACKAGE/ORDER I FOR ATIO
TOP VIEW
RUN 1
ITH 2
VFB 3
GND 4
8 PLL LPF
7 SYNC/MODE
6 VIN
5 SW
MS8 PACKAGE
8-LEAD PLASTIC MSOP
TJMAX = 125°C, θJA = 150°C/ W
ORDER PART
NUMBER
LTC1878EMS8
MS8 PART MARKING
LTNX
Consult factory for Industrial and Military grade parts.
ELECTRICAL CHARACTERISTICS
The q denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C.
VIN = 3.6V unless otherwise specified.
SYMBOL PARAMETER
CONDITIONS
MIN TYP MAX
IVFB
VFB
VOVL
VFB
VLOADREG
VIN
IQ
fOSC
fSYNC
IPLL LPF
RPFET
RNFET
Feedback Current
Regulated Output Voltage
Output Overvoltage Lockout
Reference Voltage Line Regulation
Output Voltage Load Regulation
Input Voltage Range
Input DC Bias Current
Pulse Skipping Mode
Burst Mode Operation
Shutdown
Oscillator Frequency
SYNC Capture Range
Phase Detector Output Current
Sinking Capability
Sourcing Capability
RDS(ON) of P-Channel MOSFET
RDS(ON) of N-Channel MOSFET
(Note 4)
(Note 4) 0°C TA 85°C
(Note 4) – 40°C TA 85°C
VOVL = VOVL – VFB
VIN = 2.65V to 6V (Note 4)
Measured in Servo Loop; VITH = 0.9V to 1.2V
Measured in Servo Loop; VITH = 1.6V to 1.2V
(Note 5)
2.65V < VIN < 6V, VSYNC/MODE = 0V, IOUT = 0A
VSYNC/MODE = VIN, IOUT = 0A
VRUN = 0V, VIN = 6V
VFB = 0.8V
VFB = 0V
fPLLIN < fOSC
fPLLIN > fOSC
ISW = 100mA
ISW = –100mA
q 4 30
0.784 0.8 0.816
q 0.74 0.8 0.84
q 20
50 110
0.05 0.2
q 0.1 0.5
q – 0.1 – 0.5
q 2.65
6
230 350
10 15
01
495 550 605
80
400 700
q3
q –3
10 20
–10 –20
0.5 0.7
0.6 0.8
UNITS
nA
V
V
mV
%/V
%
%
V
µA
µA
µA
kHz
kHz
kHz
µA
µA
2


Part Number LTC1878
Description High Efficiency Monolithic Synchronous Step-Down Regulator
Maker Linear Technology
Total Page 16 Pages
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