33702 Datasheet, PDF (15/24 Pages) Motorola, Inc – 3.0 A Switch-Mode Power Supply with Linear Regulator

Freescale Semiconductor, Inc.
Watchdog Closed
No Watchdog Clear Allowed
Window Open
for Watchdog Clear
50% of Watchdog Period
Watchdog Period
Timing Selected via 1²C Bus – See Table 1
Window Watchdog
Window Open for Watchdog Clear
Watchdog Period
Timing Selected via I²C Bus – See Table 1
Time-Out Watchdog
Figure 9. Watchdog Operation
Table 1. Watchdog Programming Command Byte
(as a 2nd Command Byte)
Address
Value
01100000
Action
1st Command
01100000
01101000
01101001
WD OFF
(Note 12)
WD 1280 ms
WinOFF
WD 320 ms
WinOFF
01101010
01101011
WD 80 ms
WinOFF
WD 20 ms
WinOFF
01101100
01101101
WD 1280 ms
WinON
WD 320 ms
WinON
01101110
01101111
WD 80 ms
WinON
WD 20 ms
WinON
Notes
12. The Watchdog feature will be turned
ON automatically after receiving any
other valid command byte changing
watchdog time.
When the Window Watchdog function is selected, the timer
cannot be cleared during the Closed Window time, which is
50% of the total watchdog period. When the watchdog is
cleared, the timer is reset and starts a new time-out period. If
the watchdog is not cleared during the Open Window time, the
RESET will become active (LOW) for a time determined by the
RC components of the RT timer plus 10 ms.
EN1 and EN2 Control Pins
These two pins permit positive logic control of the Enable
function and selection of the Power Sequencing mode
concurrently. Table 2 depicts the EN1 and EN2 function and
Power Sequencing mode selection.
Both EN1 and EN2 pins have internal pull-down resistors
and both can withstand a short circuit to the supply voltage,
6.0 V.
Table 2. Operating Mode Selection
EN1
EN2
Operating Mode
0
0
Regulators Disabled
0
1
Standard Power Sequencing
1
0
Inverted Power Sequencing
1
1
Regulators Enabled,
No Power Sequencing
Power Sequencing Modes
The power sequencing of the two outputs of this power
supply IC is in compliance with the Motorola Power QUICC and
other 32-bit microprocessor requirements. When the input
voltage is applied, the switcher and linear regulator outputs
follow the supply rail voltage during power-up and power-down
in the limits given by the microcontroller power sequencing
specification, illustrated in Figures 10 through 12. There are two
possible power sequencing modes, Standard and Inverted, as
explained in more detail below. The third mode of operation is
Power Sequencing Disabled.
3.3 V Input Supply (I/O Voltage)
∆V = 2.0 V
Max. Lead
V Start-Up
Slope
1.0 V/ms
(typ.)
1.8 V Core Voltage
∆V = 2.0 V
Max. Lead
∆V = 0.4 V
Max. Lag
Figure 10. Standard Power Up/Down Sequence
in +3.3 V Supply System
∆V = 2.0 V
Max. Lead
V Start-Up
5.0 V Input Supply
3.3 V I/O Voltage (V_LDO)
1.8 V Core Voltage (V_OUT)
∆V = 0.4 V
Max. Lag
∆V = 0.4 V
Max. Lag
∆V = 2.0 V
Max. Lead
Figure 11. Standard Power Up/Down Sequence
in +5.0 V Supply System
MOTOROLA ANALOG INTEGRATED CI_FRC_oU_rIT_MD_oE_rV_eICE_InD_fA_oT_rA_{mation On This Product,}
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33702
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