MPS MP5515 User Manual page 22

The MP5515 enters buck mode if VIN fails
during the cap test. The cap test cannot be
done in buck mode. For more information on
the cap health test, refer to the application note
"MP5515
AN125,
Measurement Accuracy and Recommended
Method."
VCC Power Management
The MP5515 internal circuits are powered by
the VCC capacitor. VCC is supplied by VIN, VB,
or V under different conditions (see Table
STRG
1).
Table 1: VCC Power Sources
Operation LDO_EN
Mode Bit
Boost
charge 0
(default)
Buck
discharge
Boost
charge
1
Buck
discharge
The LDO_EN (0x1Bh bit[1]) is useful for ADC
conversion, including the cap test when VIN
and VB are low. It is recommended to enable
the LDO_EN bit before ADC operation when
VIN and VB are low. Refer to the 10-Bit ADC
section on page 23 for more details.
A capacitor no less than 1µF is required on
VCC. When starting up from 3V or a lower VIN,
VCC is low due to the VIN-to-VCC voltage drop.
Any external current on VCC (i.e.: a PFI pull-up
resistor) pulls VCC lower and makes the
MP5515 difficult to start up. Typically, a 100kΩ
pull-up resistor for PFI and INT is suggested,
but these pins can also be pulled up to VB if the
VB voltage is lower than 5V.
The MP5515 can start up from a 2.7V low input
power at 25°C or a higher temperature. If the
temperature is lower than 25°C, the UVLO rises
slightly. One external Schottky diode from VIN
to VCC is suggested if the IC needs to start up
with 2.7V under low-temperature conditions.
This diode is recommended even if VIN is 3V
under -40°C.
MP5515 Rev. 1.02
1/18/2018 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
MP5515 – ENERGY BACKUP AND MANAGEMENT UNIT
Capacitor Health
Power Sources
VCC is supplied by the
higher value of either VIN
or VB.
VCC is supplied by the
higher value of either VIN
or VB when it is above
4.5V (typical value). If
VCC is lower than 4.5V,
the LDO from V to
STRG
VCC is enabled and
regulates the VCC at
about 4.5V.
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Enable Control (EN)
The EN pin of the MP5515 works together with
the EN bit to enable the internal circuit. The
MP5515 is enabled after both the EN pin and
EN bit are high. During application, the EN pin
cannot be connected to a voltage higher than
6.5V. For resistor pull-up condition, an internal
Zener diode clamps the voltage at the EN pin.
The maximum pull-up current (assuming the
worst case, 6V) for the internal Zener clamp
should be less than 1mA. When pulled up to
VIN and VB, 100kΩ pull-up resistors to both
VIN and VB are recommended.
SAS Function
The MP5515 provides a forced backup mode
for energy discharge. When SAS or the Force
Buck Release bit is high, the ISOFET turns off,
operates in buck release mode, and PFI drops
low to indicate the power status. If VB drops to
UVLO before SAS resets, the buck shuts down,
and the VCC power continues working. The
MP5515 works with a new start cycle when
SAS resets. If VB is still higher than UVLO after
SAS resets to 0, PFI is pulled high, and the
ISOFET works as the VIN power recovery after
VB triggers VB_UVLO.
Input Power Failure Indicator (PFI)
If DET drops below 0.99 x V
pulls PFI low internally to indicate a power
failure. Simultaneously, the MP5515 exits boost
mode. If the DET voltage rises to 1.02 x V
, PFI is set to high again (if pulled up by a
REF
resistor externally), but the MP5515 does not
exit buck mode, even if PFI is high, until the
V energy is discharged to UVLO or the IC
STRG
resets.
Bus Voltage Power Good Indicator (PGB)
When the voltage on the FBB (VB feedback)
drops below 0.9 x V
FBB-REF
PGB low internally. When the FBB voltage is
above 0.95 x V , PGB goes high.
FBB-REF
STRG Voltage Power Good Indicator (PGS)
The storage power good threshold can be
programmed by the PGS Threshold bits. By
default, the PGS falling threshold is 95% of the
reference voltage. When the voltage on FBS
(V feedback) drops below 0.95 x V
STRG
the MP5515 pulls PGS low internally.
, the MP5515
DET-REF
DET-
, the MP5515 pulls
,
FBS-REF
22