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

LTC3857
Electrical Characteristics The l denotes the specifications which apply over the full operating
junction 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
V_LOADREG Output Voltage Load Regulation
(Note4)
Measured in Servo Loop,
l
∆I_TH Voltage = 1.2V to 0.7V
(Note4)
Measured in Servo Loop,
l
∆I_TH Voltage = 1.2V to 2V
g_m1,2
Transconductance Amplifier g_m
(Note 4) I_TH1,2 = 1.2V, Sink/Source = 5µA
I_Q
Input DC Supply Current
(Note 5)
Pulse-Skipping or Forced Continuous
Mode (One Channel On)
RUN1 = 5V and RUN2 = 0V or
RUN1 = 0V and RUN2 = 5V,
V_FB1 = 0.83V (No Load)
Pulse-Skipping or Forced Continuous RUN1,2 = 5V, V_FB1,2 = 0.83V (No Load)
Mode (Both Channels On)
0.01
0.1
%
–0.01
2
–0.1
%
mmho
1.3
mA
2
mA
Sleep Mode (One Channel On)
Sleep Mode (Both Channels On)
Shutdown
RUN1 = 5V and RUN2 = 0V or
RUN1 = 0V and RUN2 = 5V,
V_FB1 = 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
Undervoltage Lockout
INTV_CC Ramping Up
INTV_CC Ramping Down
l
4.0
4.2
V
l 3.6
3.8
4
V
V_OVL
I_SENSE+
I_SENSE–
Feedback Overvoltage Protection
SENSE⁺ Pin Current
SENSE^– Pins Current
Measured at V_FB1,2, Relative to Regulated V_FB1,2
Each Channel
Each Channel
VV_{SSEENNSSEE––}
<
>
INTV_CC
INTV_CC
–
+
0.5V
0.5V
7
10
13
%
±1
µA
±1
µA
550
700
µA
DF_MAX
Maximum Duty Factor
In Dropout, FREQ = 0V
98
99.4
%
I_TRACK/SS1,2 Soft-Start Charge Current
V_TRACK1,2 = 0V
0.7
1
1.4
µA
V_RUN1,2 On RUN Pin On Threshold
V_RUN1, V_RUN2 Rising
l 1.21 1.26
1.31
V
V_RUN1,2 Hyst RUN Pin Hysteresis
50
mV
V_SENSE(MAX) Maximum Current Sense Threshold
V_FB1,2 = 0.7V, V_SENSE1–,₂– = 3.3V, I_LIM = 0
l 22
30
36
mV
V_FB1,2 = 0.7V, V_SENSE1–,₂– = 3.3V, I_LIM = FLOAT l 43
50
57
mV
V_FB1,2 = 0.7V, V_SENSE1–,₂– = 3.3V, I_LIM = INTV_CC l 64
75
85
mV
Gate Driver
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/BG t_1D
TG Transistion Time:
Rise Time
Fall Time
BG Transistion 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 C_LOAD = 3300pF Each Driver
Top Switch-On Delay Time
30
ns
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