English
Language : 

LTC3858 Datasheet, PDF (4/38 Pages) Linear Technology – Low IQ, Dual 2-Phase Synchronous Step-Down Controller
LTC3858
Electrical Characteristics The l denotes the specifications which apply over the full operating
junction temperature range, otherwise specifications are at TA = 25°C. VIN = 12V, VRUN1,2 = 5V, EXTVCC = 0V unless otherwise noted.
SYMBOL PARAMETER
CONDITIONS
MIN TYP MAX UNITS
TG/BG t1D Top Gate Off to Bottom Gate On Delay
Synchronous Switch-On Delay Time
CLOAD = 3300pF Each Driver
30
ns
BG/TG t1D Bottom Gate Off to Top Gate On Delay
Top Switch-On Delay Time
CLOAD = 3300pF Each Driver
30
ns
tON(MIN)
Minimum On-Time
(Note 7)
95
ns
INTVCC Linear Regulator
VINTVCCVIN
VLDOVIN
VINTVCCEXT
VLDOEXT
VEXTVCC
Internal VCC Voltage
INTVCC Load Regulation
Internal VCC Voltage
INTVCC Load Regulation
EXTVCC Switchover Voltage
6V < VIN < 38V, VEXTVCC = 0V
ICC = 0mA to 50mA, VEXTVCC = 0V
6V < VEXTVCC < 13V
ICC = 0mA to 50mA, VEXTVCC = 8.5V
EXTVCC Ramping Positive
4.85
5.1
5.35
V
0.7
1.1
%
4.85
5.1
5.35
V
0.6
1.1
%
4.5
4.7
4.9
V
VLDOHYS
EXTVCC Hysteresis Voltage
250
mV
Oscillator and Phase-Locked Loop
f25kΩ
f65kΩ
f105kΩ
Programmable Frequency
Programmable Frequency
Programmable Frequency
RFREQ = 25k, PLLIN/MODE = DC Voltage
RFREQ = 65k, PLLIN/MODE = DC Voltage
RFREQ = 105k, PLLIN/MODE = DC Voltage
105
kHz
375 440 505
kHz
835
kHz
fLOW
Low Fixed Frequency
VFREQ = 0V, PLLIN/MODE = DC Voltage
320 350 380
kHz
fHIGH
High Fixed Frequency
VFREQ = INTVCC, PLLIN/MODE = DC Voltage
485 535 585
kHz
fSYNC
Synchronizable Frequency
PGOOD1 and PGOOD2 Outputs
PLLIN/MODE = External Clock
l 75
850
kHz
VPGL
IPGOOD
PGOOD Voltage Low
PGOOD Leakage Current
IPGOOD = 2mA
VPGOOD = 5V
0.2
0.4
V
±1
µA
VPG
PGOOD Trip Level
VFB with Respect to Set Regulated Voltage
VFB Ramping Negative
Hysteresis
–13 –10
–7
%
2.5
%
VFB with Respect to Set Regulated Voltage
VFB Ramping Positive
Hysteresis
7
10
13
%
2.5
%
tPG
Delay for Reporting a Fault (PGOOD Low)
25
µs
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Ratings for extended periods may affect device reliability and
lifetime.
Note 2: The LTC3858E is guaranteed to meet performance specifications
from 0°C to 85°C. Specifications over the –40°C to 125°C operating
junction temperature range are assured by design, characterization and
correlation with statistical process controls. The LTC3858I is guaranteed
over the full –40°C to 125°C operating junction temperature range.
Note 3: TJ is calculated from the ambient temperature TA and power
dissipation PD according to the following formula:
TJ = TA + (PD • 34°C/W)
Note 4: The LTC3858 is tested in a feedback loop that servos VITH1,2 to a
specified voltage and measures the resultant VFB1,2. The specification at
85°C is not tested in production. This specification is assured by design,
characterization and correlation to production testing at 125°C.
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 ≥ of 40% IMAX (See Minimum On-Time
Considerations in the Applications Information section).
3858fa