LTC3868-1 Datasheet, PDF (4/38 Pages) Linear Technology – Low IQ, Dual 2-Phase Synchronous Step-Down Controller

LTC3868-1
Electrical Characteristics The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T_A = 25°C. V_IN = 12V, V_RUN1,2 = 5V, EXTV_CC = 0V unless otherwise noted.
SYMBOL PARAMETER
CONDITIONS
MIN TYP MAX UNITS
TG1,2 t_r
TG1,2 t_f
BG1,2 t_r
BG1,2 t_f
TG/BG t_1D
TG Transition Time:
Rise Time
Fall Time
BG Transition Time:
Rise Time
Fall Time
Top Gate Off to Bottom Gate On Delay
Synchronous Switch-On Delay Time
(Note 6)
C_LOAD = 3300pF
C_LOAD = 3300pF
(Note 6)
C_LOAD = 3300pF
C_LOAD = 3300pF
C_LOAD = 3300pF Each Driver
25
ns
16
ns
28
ns
13
ns
30
ns
BG/TG t_1D Bottom Gate Off to Top Gate On Delay
Top Switch-On Delay Time
C_LOAD = 3300pF Each Driver
30
ns
t_ON(MIN)
Minimum On-Time
INTV_CC Linear Regulator
V_INTVCCVIN Internal V_CC Voltage
V_LDOVIN
INTV_CC Load Regulation
V_INTVCCEXT Internal V_CC Voltage
V_LDOEXT
INTV_CC Load Regulation
V_EXTVCC
EXTV_CC Switchover Voltage
V_LDOHYS
EXTV_CC Hysteresis
Oscillator and Phase-Locked Loop
(Note 7)
6V < V_IN < 24V, V_EXTVCC = 0V
I_CC = 0mA to 50mA, V_EXTVCC = 0V
6V < V_EXTVCC < 13V
I_CC = 0mA to 50mA, V_EXTVCC = 8.5V
EXTV_CC Ramping Positive
95
ns
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
250
mV
f_25kΩ
Programmable Frequency
f_65kΩ
Programmable Frequency
f_105kΩ
Programmable Frequency
f_LOW
Low Fixed Frequency
f_HIGH
High Fixed Frequency
f_SYNC
Synchronizable Frequency
PGOOD1 Output
R_FREQ = 25k, PLLIN/MODE = DC Voltage
105
kHz
R_FREQ = 65k, PLLIN/MODE = DC Voltage
375
440
505
kHz
R_FREQ = 105k, PLLIN/MODE = DC Voltage
835
kHz
V_FREQ = 0V, PLLIN/MODE = DC Voltage
320
350
380
kHz
V_FREQ = INTV_CC, PLLIN/MODE = DC Voltage
485
535
585
kHz
PLLIN/MODE = External Clock
l 75
850
kHz
V_PGL
I_PGOOD
V_PG
PGOOD1 Voltage Low
PGOOD1 Leakage Current
PGOOD1 Trip Level
I_PGOOD = 2mA
V_PGOOD = 5V
V_FB with Respect to Set Regulated Voltage
V_FB Ramping Negative
Hysteresis
0.2
0.4
V
±1
µA
–13
–10
–7
%
2.5
%
V_FB with Respect to Set Regulated Voltage
V_FB Ramping Positive
Hysteresis
7
10
13
%
2.5
%
t_PG
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 LTC3868E-1 is guaranteed to meet performance specifications
from 0°C to 85°C. Specifications over the –40°C to 85°C operating
temperature range are assured by design, characterization and correlation
with statistical process controls. The LTC3868I-1 is guaranteed over the
full –40°C to 85°C operating temperature range.
Note 3: T_J is calculated from the ambient temperature T_A and power
dissipation P_D according to the following formula:
T_J = T_A + (P_D • θ_JA)
where θ_JA = 43°C for the QFN package and θ_JA = 90°C for the SSOP
package.
Note 4: The LTC3868-1 is tested in a feedback loop that servos V_ITH1,2 to a
specified voltage and measures the resultant V_FB1,2.
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_MAX (See Minimum On-Time
Considerations in the Applications Information section).
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