A4408
Adjustable Frequency Buck or Buck-Boost Pre-Regulator with a
Synchronous Buck, 3 Internal LDOs, Watchdog Timer, NPOR, and FF0/FF1
DESCRIPTION
FEATURES AND BENEFITS
• Automotive AEC-Q100 qualified
The A4408 is power management IC that uses a buck or
buck-boost pre-regulator to efficiently convert automotive
battery voltages into a tightly regulated intermediate voltage,
complete with control, diagnostics, and protections. The
output of the pre-regulator supplies a 5 V/115 mAMAX
tracking/protected LDO, a 3.3 V/ 165 mAMAX LDO, a
5V/325 mAMAX LDO, and an adjustable output synchronous
buck regulator (1.25 VTYP/700 mADC). Designed to supply
CAN or microprocessor power supplies in high-temperature
environments, the A4408 is ideal for underhood applications.
• 2.8 to 36 VIN operating range, 40 VIN maximum
• Buck or buck-boost pre-regulator (VREG)
• Adjustable PWM switching frequency: 250 kHz to 2.4 MHz
• PWM frequency can be synchronized to external clock
• Adjustable synchronous buck regulator (1.25 VNOM
• 3.3V (3V3) and 5V (V5) internal LDO regulators with
foldback short-circuit protections
)
• 5V (V5P) internal tracking LDO regulator with foldback
short-circuit and short-to-battery protections
• TRACK sets either 3V3 or V5 as the reference for V5P
• Power-on reset (NPOR) with fixed delay of 15 ms
• Programmable watchdog timer with activation delay
Enable inputs to the A4408 include a logic-level (ENB) and
two high-voltage (ENBAT1 and ENBAT2) inputs. TheA4408
provides flexibility by including a TRACK pin to set the
reference of the tracking regulator to either the 5V or the 3.3 V
output, so theA4408 can be adapted across multiple platforms
with different sensors and supply rails. The MODE pin selects
the NPOR undervoltage threshold for the V5 and V5Poutputs.
• Active-low watchdog timer enable pin (WDENn
)
• Dual bandgaps for increased reliability: BGVREF, BGFAULT
• MODE pin sets the NPOR undervoltage threshold for V5
and V5P
• Fixed POK5V undervoltage threshold for V5 and V5P
• Logic enable input (ENB) for microprocessor control
• Two ignition enable inputs (ENBAT1 and ENBAT2)
Diagnostic outputs from the A4408 include a power-on-reset
output (NPOR). POK5V indicates the status of the 5 V and
5 V protected LDOs. Fault Flag 0 (FF0) and Fault Flag 1 (FF1)
retainthelastfaulttoresetthemicrocontroller. Dualbandgaps,
one for regulation and one for fault checking, improve long-
term reliability of the A4408.
Continued on next page...
APPLICATIONS
□ Electronic Power Steering (EPS)
□ Transmission Control Units (TCU)
□ Advanced Braking Systems (ABS)
□ Emissions Control Modules
TheA4408 contains a watchdog timer that can be programmed
to accept a wide range of clock frequencies (WDADJ). The
watchdog timer has a fixed activation delay to accommodate
processorstartup. Thewatchdogtimerhasanenable/disablepin
(active low, WDENn) to facilitate initial factory programming
or field reflash programming.
□ Other automotive applications
PACKAGE: 38-Pin eTSSOP (suffix LV)
Protection features include under- and overvoltage lockout on
all four CPU supply rails. In case of a shorted output, all linear
regulatorsfeaturefoldbackovercurrentprotection.Inaddition,
Continued on next page...
Not to scale
3.3 V LDO
(3V3)
5.35 V
(VREG)
Buck-Boost
Pre-Regulator
1.25 V
(1V25)
Synchronous Buck
Regulator
Programmable
5 V LDO
(V5)
with Foldback
Protection
5 V LDO
(V5P)
Watchdog Timer
with Tracking,
Foldback, and
Short to VBAT
Protection
with Foldback
with Activation
Delay
Protection
3V3
V5
FF0 / FF1,
UV, HIC,
TSD, WD
Tracking
Control
2:1 MUX
Dual
Bandgaps
Charge
Pump
POK5V
Output
NPOR
Output
REF
Figure 1: A4408 Simplified Block Diagram
A4408-DS, Rev. 1
January 27, 2017
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