Datasheet

3
LTC3776
3776fa
ELECTRICAL CHARACTERISTICS
The ● denotes specifications that apply over the full operating temperature
range, otherwise specifications are at T
A
= 25°C. V
IN
= 4.2V unless otherwise specified.
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: The LTC3776E is guaranteed to meet specified performance from
0°C to 70°C. Specifications over the –40°C to 85°C operating range are
assured by design, characterization and correlation with statistical process
controls.
Note 3: T
J
is calculated from the ambient temperature T
A
and power
dissipation P
D
according to the following formula:
T
J
= T
A
+ (P
D
• θ
JA
°C/W)
Note 4: Dynamic supply current is higher due to gate charge being
delivered at the switching frequency.
Note 5: The LTC3776 is tested in a feedback loop that servos I
TH
to a
specified voltage and measures the resultant V
FB
voltage.
Note 6: Peak current sense voltage is reduced dependent on duty cycle to
a percentage of value as shown in Figure 2.
PARAMETER CONDITIONS MIN TYP MAX UNITS
Output Voltage Load Regulation I
TH
= 0.9V (Note 5) 0.12 0.5 %
I
TH
= 1.7V –0.12 –0.5 %
V
FB1
Input Current (Note 5) 10 50 nA
Overvoltage Protect Threshold Measured at V
FB
with Respect to 10 13.3 16 %
Regulated Feedback Voltage
Overvoltage Protect Hysteresis 3%
Top Gate (TG) Drive 1, 2 Rise Time C
L
= 3000pF 40 ns
Top Gate (TG) Drive 1, 2 Fall Time C
L
= 3000pF 40 ns
Bottom Gate (BG) Drive 1, 2 Rise Time C
L
= 3000pF 50 ns
Bottom Gate (BG) Drive 1, 2 Fall Time C
L
= 3000pF 40 ns
Maximum Current Sense Voltage (Channel 1) IPRG1 = Floating (Note 6) ● 110 125 140 mV
(SENSE1
+
– SW1)(ΔV
SENSE(MAX)
) (SOURCE) IPRG1 = 0V ● 70 85 100 mV
IPRG1 = V
IN
● 185 204 223 mV
Maximum Current Sense Voltage (Channel 2) IPRG2 = Floating (Note 6)
● 127 147 167 mV
(SENSE2
+
– SW2)(ΔV
SENSE(MAX)
) (SOURCE) IPRG2 = 0V ● 85 100 115 mV
IPRG2 = V
IN
● 215 245 275 mV
Minimum Current Sense Voltage (Channel 2 Only) IPRG2 = Floating (Note 6) ● –130 –112 –94 mV
(SENSE2
+
– SW2)(ΔV
SENSE(MAX)
) (SINK) IPRG2 = 0V ● –90 –75 –60 mV
IPRG2 = V
IN
● –208 –188 –168 mV
Soft-Start Time Time for V
FB1
to Ramp from 0.05V to 0.55V 0.667 0.833 1 ms
Oscillator and Phase-Locked Loop
Oscillator Frequency Spread Spectrum Disabled (SYNC/SSEN = GND)
PLLLPF = Floating
● 460 550 610 kHz
PLLLPF = 0V ● 260 300 340 kHz
PLLLPF = V
IN
● 650 750 825 kHz
Spread Spectrum Frequency Range SYNC/SSEN = V
IN
Minimum Switching Frequency 450 kHz
Maximum Switching Frequency 580 kHz
Phase-Locked Loop Lock Range SYNC/SSEN Clocked
Minimum Synchronizable Frequency ● 200 250 kHz
Maximum Synchronizable Frequency
● 850 1150 kHz
Phase Detector Output Current
Sinking f
OSC
> f
SYNC/FCB
–4 μA
Sourcing f
OSC
< f
SYNC/FCB
4 μA
PGOOD Output
PGOOD Voltage Low I
PGOOD
Sinking 1mA 125 mV
PGOOD Trip Level V
FB
with Respect to Set Output Voltage
V
FB
< Regulated Feedback Voltage, Ramping Positive –13 –10.0 –7 %
V
FB
< Regulated Feedback Voltage, Ramping Negative –16 –13.3 –10 %
V
FB
> Regulated Feedback Voltage, Ramping Negative 7 10.0 13 %
V
FB
> Regulated Feedback Voltage, Ramping Positive 10 13.3 16 %