ltc3851-1 Linear Technology Corporation, ltc3851-1 Datasheet - Page 4

• Manufacturer Part Number: ltc3851-1
• Description: Synchronous Step-down Switching Regulator Controller
• Manufacturer: Linear Technology Corporation

LTC3851-1
ELECTRICAL CHARACTERISTICS
SYMBOL
Oscillator and Phase-Locked Loop
f
f
f
R
I
PGOOD Output
V
I
V
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 LTC3851E-1 is guaranteed to meet performance specifications
from 0°C to 85°C. Specifications over the –40°C to 85°C operating
junction temperature range are assured by design, characterization and
correlation with statistical process controls. The LTC3851I-1 is guaranteed
over the –40°C to 125°C operating junction temperature range.
Note 3: T
dissipation P
TYPICAL PERFORMANCE CHARACTERISTICS
4
junction temperature range, otherwise specifi cations are at T
NOM
LOW
HIGH
FREQ
PGOOD
PGL
PG
MODE/PLLIN
LTC3851MSE-1: T
LTC3851UD-1: T
100
20
10
90
80
70
60
50
40
30
0
10
Effi ciency vs Output Current and
Mode
V
V
J
IN
OUT
is calculated from the ambient temperature T
BURST
= 12V
D
= 1.5V
according to the following formulas:
PARAMETER
Nominal Frequency
Lowest Frequency
Highest Frequency
MODE/PLLIN Input Resistance
Phase Detector Output Current
PGOOD Voltage Low
PGOOD Leakage Current
PGOOD Trip Level
100
PULSE
Sinking Capability
Sourcing Capability
LOAD CURRENT (mA)
SKIP
J
J
= T
CCM
= T
A
1000
A
+ (P
+ (P
D
D
• 68°C/W)
• 90°C/W)
10000
38511 G01
100000
A
100
and power
90
80
70
60
40
30
20
10
50
CONDITIONS
R
R
R
f
f
I
V
V
0
MODE
MODE
PGOOD
PGOOD
FB
10
FREQ
FREQ
FREQ
V
V
Effi ciency vs Output Current
and Mode
FB
FB
with Respect to Set Regulated Voltage
BURST
Ramping Negative
Ramping Positive
PULSE
> f
< f
= 60k
= 160k
= 36k
= 2mA
SKIP
= 5V
OSC
OSC
The
100
A
LOAD CURRENT (mA)
= 25°C. V
l
CCM
denotes the specifi cations which apply over the full operating
1000
Note 4: The LTC3851-1 is tested in a feedback loop that servos V
specified voltage and measures the resultant V
Note 5: Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency. See Applications Information.
Note 6: Rise and fall times are measured using 10% and 90% levels. Delay
times are measured using 50% levels.
Note 7: The minimum on-time condition is specified for an inductor
peak-to-peak ripple current ~40% of I
Considerations in the Applications Information section).
V
V
FIGURE 11 CIRCUIT
IN
IN
OUT
= 12V
= 15V, V
= 3.3V
10000
38511 G02
RUN
100000
= 5V unless otherwise noted.
100
90
80
70
60
50
40
30
20
10
0
10
Effi ciency vs Output Current and
Mode
PULSE
MIN
480
220
710
–12
SKIP
MAX
BURST
8
100
(see Minimum On-Time
LOAD CURRENT (mA)
FB
CCM
TYP
500
250
750
100
–10
–10
0.1
10
10
.
1000
MAX
530
280
790
0.3
±1
–8
12
10000
V
V
IN
OUT
ITH
= 12V
38511 G03
= 5V
to a
UNITS
100000
38511f
kHz
kHz
kHz
kΩ
μA
μA
μA
%
%
V