mc33702 Freescale Semiconductor, Inc, mc33702 Datasheet - Page 17

• Manufacturer Part Number: mc33702
• Description: 3.0 A Switch-mode Power Supply With Linear Regulator
• Manufacturer: Freescale Semiconductor, Inc

Inverted Power Sequencing Control
switcher (V
Standard Operating Mode
1. Single 3.3 V Supply, V
switcher supplies core voltage (e.g., 1.8 V nominal), and the
LDO operates independently (see
sequencing depends only on the normal switcher intrinsic
operation to control the Buck High-Side FET.
Power Up
point and the Buck High-Side FET will be on. In order not to
exceed the 2.0 V differential requirement between the I/O (V
and the core (V
and be able to maintain the 2.0 V or less differential. The
maximum slew rate for V
Power Down
therefore the Buck High-Side FET will be on. In the case where
V
attempt to maintain V
MOTOROLA ANALOG INTEGRATED CIRCUIT DEVICE DATA
OUT
1. V
2. V
3. V
4. V
5. V
6. V
Comparators monitor voltage differences between the
The 3.3 V supplies the microprocessor I/O voltage, the
When V
When V
can be forced off. This occurs whenever the V
voltage exceeds the LDO output voltage by more than
1.8 V.
the switcher V
voltage exceeds the LDO output voltage by more than
1.9 V, a 1.0
V
LDO output shorts to ground and for power-down in case
of V
V
V
voltage is less than 1.7 V above the LDO output voltage.
forced off. This occurs whenever the V
V
This occurs when the LDO output voltage exceeds the
V
resumes when V
is falling faster than V
OUT
OUT
OUT
OUT
OUT
OUT
OUT
LDO
OUT
OUT
OUT
IN1
IN
IN
.
. Normal operation resumes when the V
OUT
load capacitor to ground. The shunt FET is used for
- 0.2 V.
> LDO + 1.8 V, turn off V
> LDO + 1.9 V, shunt V
< LDO + 1.7 V, cancel (1) and (2) above, re-enable
< LDO - 0.2 V, turn off LDO. The LDO can be
< LDO - 0.3 V, turn on the 1.0
output by more than 300 mV.
> LDO, reset (4) and (5) above. Normal operation
is rising, initially V
is falling, V
V
OUT
pin) and LDO (LDO pin) outputs as follows:
IN2
), the switcher must start up at 2.0 V or less
OUT
shunt FET is turned on that discharges the
with LDO output falling faster than the
OUT
OUT
is insufficient and the V
OUT
IN
. In the case where V
> LDO.
IN
is 1.0 V/ms.
IN
will be below the regulation point;
= V
, the Buck High-Side FET will
OUT
IN1
Figure
OUT
will be below the regulation
Freescale Semiconductor, Inc.
OUT
= V
For More Information On This Product,
to ground. If turning off
IN2
. The switcher V
10, page 15). Power
= 3.3 V
OUT
LDO sink FET.
IN
OUT
is falling faster
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is less than
OUT
OUT
output
output
output
OUT
IN
)
than V
load capacitor will be discharged through the Buck High-Side
FET to V
voltage (V
than a maximum of 0.4 V.
Shorted Load
2. Single 5.0 V Supply, V
switcher supplies the core (e.g., 1.8 V nominal) (see
page 15).
Power Up
current and capacitance, and the relative rise times of the V
and V
Power Down
capacitance and the relative fall times of the V
supplies. There are 2 cases:
1. V
2. V
3. V
1. LDO rises faster than V
2. V
1. V
2. LDO falls faster than V
V
The LDO supplies the microprocessor I/O voltage. The
This condition depends upon the regulator current limit, load
This condition depends upon the regulator load current and
In the case V
both the Buck High-Side FET and the LDO external Pass
FET, and will discharge the LDO load capacitor into the V
supply.
IN2
exceed the core voltage by more than 2.0 V. No load
protection.
capacitance is discharged, the core voltage will exceed
the I/O voltage by more than 0.4 V. By the intrinsic
operation of the switcher, the load capacitor will be
discharged rapidly through the Buck High-Side FET to
V
protected by current limit and thermal limit.
methods (1) and (2) described in the
section, page 16.
methods (4) and (5) described in the
section, page 16.
methods (1) and (2) described in the
section, page 16.
methods (4) and (5) described in the
section, page 16.
IN2
OUT
OUT
IN
IN
OUT
OUT
OUT
.
IN
shorted to ground. Until the switcher load
supplies. There are 2 cases:
OUT
, the Buck High-Side FET is also on, and the V
. Thus, provided V
shorted to ground. This will cause the I/O voltage to
shorted to supply. No load protection. 33702
rises faster than LDO. The switcher uses control
falls faster than LDO. The LDO uses control
) will not exceed the I/O voltage (V
IN1
= V
IN2
, the intrinsic operation will turn on
IN1
OUT
IN
OUT
= V
does not fall too fast, the core
. The switcher uses control
. The LDO uses control
IN2
, or Dual Supply V
Methods of Control
Methods of Control
Methods of Control
Methods of Control
IN1
IN
and V
) by more
Figure
IN2
IN1
OUT
33702
11,
IN1
IN
17