LTC3725 Datasheet, PDF (3/20 Pages) Linear Technology – Single-Switch Forward Controller and Gate Driver

LTC3725
ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T_A = 25°C. V_CC = 12V, GND = PGND = 0V, T_A = 25°C, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN TYP MAX UNITS
Undervoltage Lockout (UVLO)
V_UVLOR
Undervoltage Lockout Threshold Rising
V_UVLOF
Undervoltage Lockout Threshold Falling
I_HUVLO
Hysteresis Current
V_UVLOOP
Voltage Feedforward Operating Range
Gate Driver (GATE)
Rising
Falling
V_UVLO = 1V
Primary-Side Control
● 1.220 1.242 1.280
V
● 1.205 1.226 1.265
V
● 4.2
4.9
5.6
µA
V_UVLOF(MIN)
3.75
V
R_OS
V_OH
I_PU
t_r
t_f
Rectifier
Output Pull-Down Resistance
High Output Voltage
Peak Pull-Up Current
Output Rise Time
Output Fall Time
I_OUT = 100mA
I_OUT = –100mA
10% to 90%, C_OUT = 4.7nF
10% to 90%, C_OUT = 4.7nF
1.9
Ω
11
V
1.7
A
40
ns
70
ns
I_RECT
Oscillator
Maximum Rectifier DC Output Current
25
mA
f_OSC(P)
Oscillator Frequency
∆f_RFS(P)
Oscillator Resistor Set Accuracy
f_OSC(S)
Oscillator Frequency
Soft-Start/Fault (SSFLT)
Primary-Side Control, R_FS(P) = 100kΩ
Primary-Side Control, R_FS(P) = 25kΩ
Primary-Side Control, R_FS(P) = 300kΩ
Primary-Side Control
25k < R_FSET < 300k
Secondary-Side Control (During Start-Up),
R_FS(S) = 100kΩ
200
kHz
700
kHz
70
kHz
±15
%
300
kHz
I_SS(C)
Soft-Start Charge Current
V_LRTO
Linear Regulator Time Out-Threshold
V_FLTH
Fault Output High
I_SS(D)
Soft-Start Discharge Current
Current Sense Input (I_S)
V_IS(MAX)
Overcurrent Threshold
Volt Second Limit (V_SLMT)
V_VSL(MAX) Volt-Second Limit Threshold
I_VSLMT(MAX) Maximum Volt-Second Limit Resistor Current
Optoisolator Bias Current
Primary-Side Control, V_SSFLT = 2V
Secondary-Side Control, V_UVLO = 1.3V,
V_SSFLT = 2V
Secondary-Side Control, V_UVLO = 3.75V,
V_SSFLT = 2V
V_CC = 8V
Timing Out After Fault, V_SSFLT = 2V
– 5.2
µA
–4
µA
– 1.6
µA
3.9
V
6.7
V
1
µA
300
mV
1.26
V
0.25
mA
V_OPTO
I_OPTO
Open Circuit Optoisolator Voltage
Optoisolator Bias Current
Primary-Side Control I_FB = 0V
Primary-Side Control V_FB = 2.5V
Primary-Side Control V_FB = 0V
3.3
V
0.5
mA
1.6
mA
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: Operating junction temperature T_J (in °C) is calculated from the
ambient temperature T_A and the average power dissipation PD (in watts)
by the formula: T_J = T_A + θ_JA • PD. Refer to the Applications Information
section for details.
Note 3: I_CC is the sum of current into NDRV and V_CC.
3725f
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