LTC3731H
4
3731Hfb
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 LTC3731H is guaranteed to meet specifications over the –40°C
to 140°C operating junction temperature range. Note that the maximum
ambient temperature is determined by specific operating conditions in
conjunction with board layout, the rated package thermal resistance and
other environmental factors.
Junction temperature (T
J
) is calculated from the ambient temperature T
A
and power dissipation PD according to the following formula:
LTC3731HG: T
J
= T
A
+ (P
D
• 70°C/W)
LTC3731HG: T
J
= T
CASE
+ (P
D
• 25°C/W)
LTC3731HUH: T
J
= T
A
+ (P
D
• 34°C/W)
High junction temperatures degrade operating lifetimes. Operating lifetime
at junction temperatures greater than 125°C is derated to 1000 hours. The
LTC3731H is tested under pulsed load conditions such that T
J
≈ T
A
.
elecTrical characTerisTics
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Power Good Output Indication
V
PGL
PGOOD Voltage Output Low I
PGOOD
= 2mA, G Package
I
PGOOD
= 1.6mA, UH Package
0.1
0.5
0.3
1
V
V
I
PGOOD
PGOOD Output Leakage V
PGOOD
= 5V 1 µA
V
PGTHNEG
V
PGTHPOS
PGOOD Trip Thresholds
V
EAIN
Ramping Negative
V
EAIN
Ramping Positive
V
EAIN
with Respect to Set Output Voltage, PGOOD
Goes Low After V
UVDLY
Delay
–7
7
–10
10
–13
13
%
%
V
PGDLY
Power Good Fault Report Delay After V
EAIN
is Forced Outside the PGOOD Thresholds 100 150 µs
Oscillator and Phase-Locked Loop
f
NOM
Nominal Frequency V
PLLFLTR
= 1.2V 360 400 440 kHz
f
LOW
Lowest Frequency V
PLLFLTR
= 0V 190 225 260 kHz
f
HIGH
Highest Frequency V
PLLFLTR
= 2.4V 600 680 750 kHz
V
PLLTH
PLLIN Input Threshold Minimum Pulse Width > 100ns 1 V
R
PLLIN
PLLIN Input Resistance 50 kΩ
I
PLLFLTR
Phase Detector Output Current
Sinking Capability
Sourcing Capability
f
PLLIN
< f
OSC
f
PLLIN
> f
OSC
20
20
µA
µA
R
RELPHS
Controller 2-Controller 1 Phase
Controller 3-Controller 1 Phase
120
240
Deg
Deg
CLKOUT Controller 1 TG to CLKOUT Phase PHASMD = 0V
PHASMD = 5V
30
60
Deg
Deg
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
CC
= V
RUN/SS
= 5V unless otherwise noted.
Note 3: The IC is tested in a feedback loop that servoes the error amplifier
output voltage to its midrange point (V
ITH
= 1.2V).
Note 4: Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency. See Applications Information.
Note 5: The minimum on-time condition corresponds to an inductor
peak-to-peak ripple current of ≥40% of I
MAX
(see minimum on-time
considerations in the Applications Information Section).
Note 6: This IC includes overtemperature protection that is intended
to protect the device during momentary overload conditions.
Overtemperature protection becomes active at a junction temperature
greater than the maximum operating temperature. Continuous operation
above the specified maximum operating junction temperature may impair
device reliability.
