LTC3728 Datasheet, PDF (3/32 Pages) Linear Technology – Dual, 550kHz, 2-Phase Synchronous Step-Down Switching Regulator

LTC3728
ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T_A = 25°C. V_IN = 15V, V_{RUN/SS1, 2} = 5V unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN TYP MAX UNITS
g_{m1, 2}
g_{mGBW1, 2}
V_FCB
I_FCB
V_BINHIBIT
Transconductance Amplifier g_m
Transconductance Amplifier GBW
Input DC Supply Current
Normal Mode
Shutdown
Forced Continuous Threshold
Forced Continuous Pin Current
Burst Inhibit (Constant Frequency)
Threshold
I_{TH1, 2} = 1.2V; Sink/Source 5uA; (Note 3)
I_{TH1, 2} = 1.2V; (Note 3)
(Note 4)
V_IN = 15V; EXTV_CC Tied to V_OUT1; V_OUT1 = 5V
V_{RUN/SS1, 2} = 0V
V_FCB = 0.85V
Measured at FCB pin
1.3
3
● 0.76
– 0.50
450
20
0.800
– 0.18
4.3
mmho
MHzI_Q
µA
35
µA
0.84
V
– 0.1
µA
4.8
V
UVLO
Undervoltage Lockout
V_IN Ramping Down
●
3.5
4
V
V_OVL
Feedback Overvoltage Lockout
Measured at V_{OSENSE1, 2}
● 0.84 0.86 0.88
V
I_SENSE
Sense Pins Total Source Current
(Each Channel); V_SENSE1–_{, 2}– = V_SENSE1+_{, 2}+ = 0V
– 85 – 60
µA
DF_MAX
Maximum Duty Factor
In Dropout
98
99.4
%
I_{RUN/SS1, 2}
Soft-Start Charge Current
V_{RUN/SS1, 2} = 1.9V
0.5
1.2
µA
V_{RUN/SS1, 2} ON RUN/SS Pin ON Threshold
V_RUN/SS1, V_RUN/SS2 Rising
1.0
1.5
1.9
V
V_{RUN/SS1, 2} LT RUN/SS Pin Latchoff Arming Threshold V_RUN/SS1, V_RUN/SS2 Rising from 3V
3.8
4.5
V
I_{SCL1, 2}
RUN/SS Discharge Current
Soft Short Condition V_{OSENSE1, 2} = 0.5V;
V_{RUN/SS1, 2} = 4.5V
0.5
2
4
µA
I_SDLHO
Shutdown Latch Disable Current
V_{OSENSE1, 2} = 0.5V
1.6
5
µA
V_SENSE(MAX) Maximum Current Sense Threshold
V_{OSENSE1, 2} = 0.7V,V_SENSE1–_{, 2} – = 5V
V_{OSENSE1, 2} = 0.7V,V_SENSE1–_{, 2} – = 5V
65
75
85
mV
● 62
75
88
mV
TG1, 2 t_r
TG1, 2 t_f
TG Transition Time:
Rise Time
Fall Time
(Note 5)
C_LOAD = 3300pF
C_LOAD = 3300pF
50
90
ns
50
90
ns
BG1, 2 t_r
BG1, 2 t_f
BG Transition Time:
Rise Time
Fall Time
(Note 5)
C_LOAD = 3300pF
C_LOAD = 3300pF
40
90
ns
40
80
ns
TG/BG t_1D
Top Gate Off to Bottom Gate On Delay
Synchronous Switch-On Delay Time C_LOAD = 3300pF Each Driver
90
ns
BG/TG t_2D
Bottom Gate Off to Top Gate On Delay
Top Switch-On Delay Time
C_LOAD = 3300pF Each Driver
90
ns
t_ON(MIN)
Minimum On-Time
Tested with a Square Wave (Note 6)
100
ns
INTV_CC Linear Regulator
V_INTVCC
Internal V_CC Voltage
6V < V_IN < 30V, V_EXTVCC = 4V
4.8
5.0
5.2
V
V_LDO INT
INTV_CC Load Regulation
I_CC = 0 to 20mA, V_EXTVCC = 4V
0.2
1.0
%
V_LDO EXT
EXTV_CC Voltage Drop
I_CC = 20mA, V_EXTVCC = 5V
80
160
mV
V_EXTVCC
EXTV_CC Switchover Voltage
I_CC = 20mA, EXTV_CC Ramping Positive
● 4.5
4.7
V
V_LDOHYS
EXTV_CC Hysteresis
0.2
V
Oscillator and Phase-Locked Loop
f_NOM
f_LOW
f_HIGH
R_PLLIN
I_PLLFLTR
Nominal Frequency
Lowest Frequency
Highest Frequency
PLLIN Input Resistance
Phase Detector Output Current
Sinking Capability
Sourcing Capability
V_PLLFLTR = 1.2V
V_PLLFLTR = 0V
V_PLLFLTR ≥ 2.4V
f_PLLIN < f_OSC
f_PLLIN > f_OSC
360 400 440
kHz
230 260 290
kHz
480 550 590
kHz
50
kΩ
–15
µA
15
µA
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