Datasheet

LTC3785
3
3785fc
The l denotes the specifications which apply over the full operating junction
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= I
SVOUT
= V
DRV
= V
BST1
= V
BST2
= 3.6V, R
T
= 49.9k, R
ILSET
= 59k.
elecTrical characTerisTics
PARAMETER CONDITIONS MIN TYP MAX UNITS
Error Amp Source Current –500 µA
Error Amp Sink Current 900 µA
Error Amp A
VOL
90 dB
Overvoltage Threshold V
SENSE
Pin % Above FB
LTC3785E
LTC3785I
l
l
6
6
10
10
14
15
%
%
Undervoltage Threshold V
SENSE
Pin % Below FB
LTC3785E
LTC3785I
l
l
–3.5
–3.5
–6.5
–6.5
–9.5
–10.5
%
%
V
SENSE
Input Current V
SENSE
= Measured FB Voltage 1 500 nA
V
CC
Regulator
V
CC
Maximum Regulating Voltage V
IN
= 5V, I
VCC
= –20mA
l
4.15 4.35 4.55 V
V
CC
Regulation Voltage V
IN
= 3.6V, I
VCC
= –20mA
l
3.3 3.5 3.6 V
V
CC
Regulator Sink Current I
SVOUT
= V
CC
= 5V 800 µA
Run/Soft-Start
RUN/SS Threshold When IC is Enabled
When EA is at Maximum Boost Duty Cycle
l
0.35 0.7
1.9
1.1 V
V
RUN/SS Input Current RUN/SS = 0V –1 µA
RUN/SS Discharge Current During Current Limit 20 30 µA
Current Limit
Current Limit Sense Threshold I
SVIN
to I
SSW1
, R
ILSET
= 121k
I
SVIN
to I
SSW1
, R
ILSET
= 59k
l
l
20
55
60
105
100
155
mV
mV
Reverse Current Limit Sense Threshold I
SSW2
to I
SVOUT
, CCM > 2V
I
SSW2
to I
SVOUT
, CCM < 0.4V, LTC3785E
I
SSW2
to I
SVOUT
, CCM < 0.4V, LTC3785I
l
l
–50 –110
–15
–15
–170
–35
–40
mV
mV
mV
Input Current I
SVIN
I
SVOUT
I
SSW1
, I
SSW2
80
10
0.1
150
20
5
µA
µA
µA
CCM Input Threshold (High)
l
2.2 V
CCM Input Threshold (Low)
l
0.4 V
CCM Input Current CCM = 3.6V 0.01 1 µA
Burst Mode Operation
Mode Threshold
l
0.8 1.5 2.2 V
Mode Input Current 0.01 1 µA
t
ON
Time 1.4 µs
Oscillator
Frequency Accuracy
l
370 509 650 kHz
Switching Characteristics
Maximum Duty Cycle Boost (% Switch BG2 On)
Buck (% Switch TG1 On)
l
80 90
99
%
%
TG1, TG2 Driver Impedance 2 Ω
BG1, BG2 Driver Impedance 2 Ω
TG1, TG2 Rise Time C
LOAD
= 3300pF (Note 3) 20 ns