LTC3857-1_15 Datasheet, PDF (3/38 Pages) Linear Technology – Low IQ, Dual, 2-Phase Synchronous Step-Down Controller

LTC3857-1
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating junction
temperature range, otherwise specifications are at T_A = 25°C (Note 2). V_IN = 12V, V_RUN1,2 = 5V, EXTV_CC = 0V unless otherwise noted.
SYMBOL PARAMETER
CONDITIONS
MIN TYP MAX UNITS
V_IN
V_FB1,2
Input Supply Operating Voltage Range
Regulated Feedback Voltage
(Note 4) I_TH1,2 Voltage = 1.2V
–40°C to 125°C
–40°C to 85°C
4
38
V
l 0.788 0.800 0.812
V
0.792 0.800 0.808
V
I_FB1,2
V_REFLNREG
V_LOADREG
Feedback Current
Reference Voltage Line Regulation
Output Voltage Load Regulation
(Note 4)
(Note 4) V_IN = 4.5V to 38V
(Note 4)
Measured in Servo Loop,
ΔI_TH Voltage = 1.2V to 0.7V
(Note 4)
Measured in Servo Loop,
ΔI_TH Voltage = 1.2V to 2V
±5
±50
nA
0.002 0.02 %/V
l
0.01 0.1
%
l
–0.01 –0.1
%
g_m1,2
I_Q
Transconductance Amplifier g_m
Input DC Supply Current
Pulse-Skipping or Forced Continuous
Mode (One Channel On)
Pulse-Skipping or Forced Continuous
Mode (Both Channels On)
(Note 4) I_TH1,2 = 1.2V, Sink/Source = 5μA
(Note 5)
RUN1 = 5V and RUN2 = 0V, V_FB1 = 0.83V (No Load) or
RUN1 = 0V and RUN2 = 5V, V_FB2 = 0.83V (No Load)
RUN1,2 = 5V, V_FB1,2 = 0.83V (No Load)
2
mmho
2
mA
2
mA
Sleep Mode (One Channel On)
Sleep Mode (Both Channels On)
Shutdown
RUN1 = 5V and RUN2 = 0V, V_FB1 = 0.83V (No Load) or
RUN1 = 0V and RUN2 = 5V, V_FB2 = 0.83V (No Load)
RUN1,2 = 5V, V_FB1,2 = 0.83V (No Load)
RUN1,2 = 0V
50
75
μA
65
120
μA
8
20
μA
UVLO
V_OVL
I_SENSE+
I_SENSE–
Undervoltage Lockout
Feedback Overvoltage Protection
SENSE⁺ Pin Current
SENSE^– Pins Current
DF_MAX
Maximum Duty Factor
I_TRACK/SS1,2 Soft-Start Charge Current
V_RUN1,2 On RUN Pin On Threshold
V_RUN1,2 Hyst RUN Pin Hysteresis
V_SENSE(MAX) Maximum Current Sense Threshold
Gate Driver
INTV_CC Ramping Up
INTV_CC Ramping Down
Measured at V_FB1,2, Relative to Regulated V_FB1,2
Each Channel
Each Channel
V_SENSE– < INTV_CC – 0.5V
V_SENSE– > INTV_CC + 0.5V
In Dropout, FREQ = 0V
V_TRACK1,2 = 0V
V_RUN1, V_RUN2 Rising
V_FB1,2 = 0.7V, V_SENSE1–,₂– = 3.3V
l
4.0 4.2
V
l 3.6
3.8
4
V
7
10
13
%
±1
μA
±1
μA
550
μA
98 99.4
%
0.7 1.0 1.4
μA
l 1.21 1.26 1.31
V
50
mV
l 43
50
57
mV
TG1,2
Pull-Up On-Resistance
Pull-Down On-Resistance
2.5
Ω
1.5
Ω
BG1,2
Pull-Up On-Resistance
Pull-Down On-Resistance
2.4
Ω
1.1
Ω
TG1,2 t_r
TG1,2 t_f
BG1,2 t_r
BG1,2 t_f
TG Transition Time:
Rise Time
Fall Time
BG Transition Time:
Rise Time
Fall Time
(Note 6)
C_LOAD = 3300pF
C_LOAD = 3300pF
(Note 6)
C_LOAD = 3300pF
C_LOAD = 3300pF
25
ns
16
ns
28
ns
13
ns
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