LTC3868 Datasheet, PDF (3/38 Pages) Linear Technology – Low IQ, Dual 2-Phase Synchronous Step-Down Controller

LTC3868
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
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 or
RUN1 = 0V and RUN2 = 5V,
V_FB1 = 0.83V (No Load)
RUN1,2 = 5V, V_FB1,2 = 0.83V (No Load)
2
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
170
250
µA
300 450
µA
8
25
µA
UVLO
Undervoltage Lockout
INTV_CC Ramping Up
INTV_CC Ramping Down
l
4
4.2
V
l 3.6
3.8
4
V
V_OVL
I_SENSE+
I_SENSE–
Feedback Overvoltage Protection
SENSE⁺ Pins Current
SENSE^– Pins Current
Measured at V_FB1,2, Relative to Regulated V_FB1,2
Each Channel
Each Channel
V_OUT1,2 < INTV_CC – 0.5V
V_OUT1,2 > INTV_CC + 0.5V
7
10
13
%
±1
µA
±1
µA
540 700
µA
DF_MAX
Maximum Duty Factor
In Dropout, FREQ = 0V
98
99.4
%
I_SS1,2
Soft-Start Charge Current
V_SS1,2 = 0V
0.7
1.0
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_SS1,2 LA SS Pin Latchoff Arming Threshold
V_SS1, V_SS2 Rising from 1V
1.9
2
2.1
V
V_SS1,2 LT SS Pin Latchoff Threshold
V_SS1, V_SS2 Falling from 2V
1.3
1.5
1.7
V
I_DSC1,2 LT SS Discharge Current
Short-Circuit Condition V_FB1,2 = 0.5V,
V_SS1,2 = 4.5V
7
10
13
µA
V_SENSE(MAX) Maximum Current Sense Threshold
V_FB1,2 = 0.7V, V_SENSE1–,₂– = 3.3V, I_LIM = 0
V_FB1,2 = 0.7V, V_SENSE1–,₂– = 3.3V, I_LIM = FLOAT
V_FB1,2 = 0.7V, V_SENSE1–,₂– = 3.3V, I_LIM = INTV_CC
22
30
36
mV
43
50
57
mV
64
75
86
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 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
(Note 7)
95
ns
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