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| LTC3850-1_15 Datasheet, PDF (4/38 Pages) Linear Technology – Dual, 2-Phase Synchronous Step-Down Switching Controller | |||
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LTC3850/LTC3850-1
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C, VIN = 15V, VRUN1,2 = 5V, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN TYP MAX UNITS
Main Control Loops
VFB1,2
IFB1,2
VREFLNREG
VLOADREG
Regulated Feedback Voltage
Feedback Current
Reference Voltage Line Regulation
Output Voltage Load Regulation
gm1,2
IQ
UVLO
UVLOHYS
DFMAX
VOVL
ISENSE
ITK/SS1,2
VRUN1,2
VRUN1,2HYS
VSENSE(MAX)
Transconductance Amplifier gm
Input DC Supply Current
Normal Mode
Shutdown
Undervoltage Lockout on INTVCC
UVLO Hysteresis
Maximum Duty Factor
Feedback Overvoltage Lockout
Sense Pin Bias Current
Soft-Start Charge Current
RUN Pin ON Threshold
RUN Pin ON Hysteresis
Maximum Current Sense Threshold
(Note 8)
TG RUP
TG Driver Pull-Up On-Resistance
TG RDOWN TG Driver Pulldown On-Resistance
BG RUP
BG Driver Pull-Up On-Resistance
BG RDOWN BG Driver Pulldown On-Resistance
TG1,2 tr
TG1,2 tf
BG1,2 tr
BG1,2 tf
TG/BG t1D
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
BG/TG t2D
Bottom Gate Off to Top Gate On Delay
Top Switch-On Delay Time
tON(MIN)
Minimum On-Time
INTVCC Linear Regulator
VINTVCC
Internal VCC Voltage
VLDO INT
INTVCC Load Regulation
VEXTVCC
EXTVCC Switchover Voltage
VLDO EXT
EXTVCC Voltage Drop
VLDOHYS
EXTVCC Hysteresis
ITH1,2 Voltage = 1.2V; (Note 4)
l
(Note 4)
VIN = 6V to 24V (Note 4)
(Note 4)
Measured in Servo Loop; DITH Voltage = 1.2V to 0.7V l
Measured in Servo Loop; DITH Voltage = 1.2V to 1.6V l
ITH1,2 = 1.2V; Sink/Source 5µA; (Note 4)
(Note 5)
VIN = 15V; EXTVCC Tied to VOUT1; VOUT1 = 5V
VRUN1,2 = 0V
VINTVCC Ramping Down
In Dropout
Measured at VFB1,2
l
(Each Channel) VSENSE1,2 = 3.3V
VTK/SS1,2 = 0V
VRUN1, VRUN2 Rising
l
VFB1,2 = 0.7V, VSENSE1,2 = 3.3V, ILIM = 0V
l
VFB1,2 = 0.7V, VSENSE1,2 = 3.3V, ILIM = Float
l
VFB1,2 = 0.7V, VSENSE1,2 = 3.3V, ILIM = INTVCC
l
TG High
TG Low
BG High
BG Low
(Note 6)
CLOAD = 3300pF
CLOAD = 3300pF
(Note 6)
CLOAD = 3300pF
CLOAD = 3300pF
CLOAD = 3300pF Each Driver
CLOAD = 3300pF Each Driver
(Note 7)
7V < VIN < 24V
ICC = 0mA to 50mA
EXTVCC Ramping Positive
l
ICC = 20mA, VEXTVCC = 5V
0.792
96
0.84
0.9
1.1
20
40
60
4.8
4.5
0.800
â10
0.002
0.01
â0.01
2.2
850
30
3
0.5
97.2
0.86
±1
1.3
1.22
80
30
50
75
2.6
1.5
2.4
1.1
25
25
25
25
30
30
90
5
0.5
4.7
50
200
0.808
â50
0.02
0.1
â0.1
50
0.88
±2
1.7
1.35
40
60
90
5.2
2
100
V
nA
%/V
%
%
mmho
µA
µA
V
V
%
V
µA
µA
V
mV
mV
mV
mV
Ω
Ω
Ω
Ω
ns
ns
ns
ns
ns
ns
ns
V
%
V
mV
mV
38501fc
4
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