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參數(shù)資料
| 型號(hào)： | PC33702DWBR2 |
| 廠商： | MOTOROLA INC |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 6 A SWITCHING REGULATOR, 400 kHz SWITCHING FREQ-MAX, PDSO32 |
| 封裝： | PLASTIC, SOIC-32 |
| 文件頁數(shù)： | 9/24頁 |
| 文件大小： | 647K |
| 代理商： | PC33702DWBR2 |
MOTOROLA ANALOG INTEGRATED CIRCUIT DEVICE DATA
33702
17
Inverted Power Sequencing Control
Comparators monitor voltage differences between the
switcher (VOUT pin) and LDO (LDO pin) outputs as follows:
1. VOUT > LDO + 1.8 V, turn off VOUT . The switcher VOUT
can be forced off. This occurs whenever the VOUT output
voltage exceeds the LDO output voltage by more than
1.8 V.
2. VOUT > LDO + 1.9 V, shunt VOUT to ground. If turning off
the switcher VOUT is insufficient and the VOUT output
voltage exceeds the LDO output voltage by more than
1.9 V, a 1.0
shunt FET is turned on that discharges the
VOUT load capacitor to ground. The shunt FET is used for
LDO output shorts to ground and for power-down in case
of VIN1 ≠ VIN2 with LDO output falling faster than the
VOUT.
3. VOUT < LDO + 1.7 V, cancel (1) and (2) above, re-enable
VOUT. Normal operation resumes when the VOUT output
voltage is less than 1.7 V above the LDO output voltage.
4. VOUT < LDO - 0.2 V, turn off LDO. The LDO can be
forced off. This occurs whenever the VOUT is less than
VLDO - 0.2 V.
5. VOUT < LDO - 0.3 V, turn on the 1.0 LDO sink FET.
This occurs when the LDO output voltage exceeds the
VOUT output by more than 300 mV.
6. VOUT > LDO, reset (4) and (5) above. Normal operation
resumes when VOUT > LDO.
Standard Operating Mode
1. Single 3.3 V Supply, VIN = VIN1 = VIN2 = 3.3 V
The 3.3 V supplies the microprocessor I/O voltage, the
switcher supplies core voltage (e.g., 1.8 V nominal), and the
LDO operates independently (see Figure 10, page 15). Power
sequencing depends only on the normal switcher intrinsic
operation to control the Buck High-Side FET.
Power Up
When VIN is rising, initially VOUT will be below the regulation
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 (VIN)
and the core (VOUT), the switcher must start up at 2.0 V or less
and be able to maintain the 2.0 V or less differential. The
maximum slew rate for VIN is 1.0 V/ms.
Power Down
When VIN is falling, VOUT will be below the regulation point;
therefore the Buck High-Side FET will be on. In the case where
VOUT is falling faster than VIN, the Buck High-Side FET will
attempt to maintain VOUT. In the case where VIN is falling faster
than VOUT, the Buck High-Side FET is also on, and the VOUT
load capacitor will be discharged through the Buck High-Side
FET to VIN. Thus, provided VIN does not fall too fast, the core
voltage (VOUT) will not exceed the I/O voltage (VIN) by more
than a maximum of 0.4 V.
Shorted Load
1. VOUT shorted to ground. This will cause the I/O voltage to
exceed the core voltage by more than 2.0 V. No load
protection.
2. VIN shorted to ground. Until the switcher load
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
VIN.
3. VOUT shorted to supply. No load protection. 33702
protected by current limit and thermal limit.
2. Single 5.0 V Supply, VIN1 = VIN2, or Dual Supply VIN1 ≠
VIN2
The LDO supplies the microprocessor I/O voltage. The
switcher supplies the core (e.g., 1.8 V nominal) (see Figure 11,
Power Up
This condition depends upon the regulator current limit, load
current and capacitance, and the relative rise times of the VIN1
and VIN2 supplies. There are 2 cases:
1. LDO rises faster than VOUT. The LDO uses control
methods (1) and (2) described in the Methods of Control
section, page 16.
2. VOUT rises faster than LDO. The switcher uses control
methods (4) and (5) described in the Methods of Control
section, page 16.
Power Down
This condition depends upon the regulator load current and
capacitance and the relative fall times of the VIN1 and VIN2
supplies. There are 2 cases:
1. VOUT falls faster than LDO. The LDO uses control
methods (1) and (2) described in the Methods of Control
section, page 16.
In the case VIN1 = VIN2, the intrinsic operation will turn on
both the Buck High-Side FET and the LDO external Pass
FET, and will discharge the LDO load capacitor into the VIN
supply.
2. LDO falls faster than VOUT. The switcher uses control
methods (4) and (5) described in the Methods of Control
section, page 16.
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