LTC3675_12 Datasheet, PDF (25/38 Pages) Linear Technology – 7-Channel Confi gurable High Power PMIC

LTC3675
OPERATION
On start-up, all PGOOD outputs are unmasked and a power-
on reset will cause RSTB to be pulled low. Once all enabled
regulators have their output PGOOD for 200ms typical
(C_T = 0.01μF) the RSTB output goes Hi-Z.
By masking a PGOOD signal, the RSTB or IRQB pin will
remain Hi-Z even though the output voltage of a regulator
may be below its PGOOD threshold. However, when the
status register is read back, the true condition of PGOOD
is reported.
UNDERVOLTAGE AND OVERTEMPERATURE
FUNCTIONALITY
The undervoltage (UV) circuit monitors the input supply
voltage and shuts down all enabled regulators if the input
voltage falls below 2.45V. The LTC3675 also provides a
user with an undervoltage warning, which indicates to the
user that the input supply voltage is approaching the UV
threshold. The undervoltage warning threshold is user
programmable as shown in Table 2.
Table 2. UV Warning Thresholds
UV[2], UV[1], UV[0]
000 (Default)
FALLING V_IN WARNING THRESHOLD
2.7V
001
2.8V
010
2.9V
011
3.0V
100
3.1V
101
3.2V
110
3.3V
111
3.4V
To prevent thermal damage to the LTC3675 and its sur-
rounding components, the LTC3675 incorporates an
overtemperature (OT) function. When the LTC3675 die
temperature reaches 150°C all enabled regulators are shut
down and remain in shutdown until the die temperature
falls to 135°C. The LTC3675 also has an overtemperature
warning function which warns a user that the die tempera-
ture is approaching the OT threshold which allows the user
to take any corrective action. The OT warning threshold is
user programmable as shown in Table 3.
Table 3. OT Warning Thresholds
OT[1], OT[0]
OT WARNING THRESHOLD
00 (Default)
10° Below OT
01
20° Below OT
10
30° Below OT
11
40° Below OT
A UV or OT warning is reported to the user when the IRQB
pin is in its high impedance state. The UV and OT warning
flags are not maskable by the user.
RESET_ALL Functionality: The RESET_ALL bit shuts down
all enabled regulators (enabled either via its enable pin or
I²C) for 1 second. All command registers are cleared and
put in their default state.
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