Datasheet

LTC1877
3
1877fb
ELECTRICAL CHARACTERISTICS
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: The LTC1877E is guaranteed to meet specifi cations from 0°C to
85°C. Specifi cations over the –40°C to 85°C operating temperature range
are assured by design, characterization and correlation with statistical
process controls. The LTC1877I is guaranteed over the full –40°C to 85°C
operating temperature range.
The l denotes the specifi cations which apply over the full operating
temperature range, otherwise specifi cations are at T
A
= 25°C. V
IN
= 5V unless otherwise specifi ed.
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
I
PLL LPF
Phase Detector Output Current
Sinking Capability
Sourcing Capability
f
PLLIN
< f
OSC
f
PLLIN
> f
OSC
l
l
3
–3
10
–10
20
–20
μA
μA
R
PFET
R
DS(ON)
of P-Channel MOSFET I
SW
= 100mA 0.65 0.85 Ω
R
NFET
R
DS(ON)
of N-Channel MOSFET I
SW
= –100mA 0.75 0.95 Ω
I
PK
Peak Inductor Current V
FB
= 0.7V, Duty Cycle < 35% 0.8 1.0 1.25 A
I
LSW
SW Leakage V
RUN
= 0V, V
SW
= 0V or 8.5V, V
IN
= 8.5V ±0.01 ±1 μA
V
SYNC/MODE
SYNC/MODE Threshold
l
0.3 1.0 1.5 V
I
SYNC/MODE
SYNC/MODE Leakage Current ±0.01 ±1 μA
V
RUN
RUN Threshold
l
0.3 0.7 1.5 V
I
RUN
RUN Input Current ±0.01 ±1 μA
Note 3: T
J
is calculated from the ambient temperature T
A
and power
dissipation P
D
according to the following formulas:
LTC1877EMS8: T
J
= T
A
+ (P
D
)(150°C/W)
Note 4: The LTC1877 is tested in a feedback loop which servos V
FB
to the
balance point for the error amplifi er (V
ITH
= 1.2V).
Note 5: Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency.
TYPICAL PERFORMANCE CHARACTERISTICS
Effi ciency vs Input Voltage Effi ciency vs Output Current Effi ciency vs Output Current
INPUT VOLTAGE (V)
0
EFFICIENCY (%)
2
4
68
1877 G01
10
100
95
90
85
80
75
70
65
60
55
50
12
V
OUT
= 2.5V
L = 10μH
Burst Mode OPERATION
I
LOAD
= 0.1mA
I
LOAD
= 1mA
I
LOAD
= 300mA
I
LOAD
= 100mA
I
LOAD
= 10mA
OUTPUT CURRENT (mA)
0.1
EFFICIENCY (%)
10
1000
1877 G02
1.0 100
V
IN
= 3.6V
V
IN
= 7.2V
V
IN
= 3.6V
V
IN
= 7.2V
100
90
80
70
60
50
40
30
20
10
0
V
OUT
= 2.5V
L = 10μH
PULSE-SKIPPING MODE
Burst Mode OPERATION
OUTPUT CURRENT (mA)
0.1
EFFICIENCY (%)
10
1000
95
90
85
80
75
70
65
60
55
1877 G03
1.0 100
L = 15μH
L = 10μH
V
IN
= 10V
V
OUT
= 3.3V
Burst Mode OPERATION