參數(shù)資料
型號(hào): FN4496
廠商: Intersil Corporation
元件分類(lèi): 基準(zhǔn)電壓源/電流源
英文描述: Advanced PWM and Dual Linear Power Control
中文描述: 先進(jìn)的雙PWM和線性功率控制
文件頁(yè)數(shù): 9/14頁(yè)
文件大小: 323K
代理商: FN4496
218
For an equation for the output inductor ripple current see the
section under component guidelines titled ‘Output Inductor
Selection’.
OUT1 Voltage Program
The output voltage of the PWM converter is programmed to
discrete levels between 1.8V
DC
and 3.5V
DC
. This output is
designed to supply the microprocessor core voltage. The
voltage identification (VID) pins program an internal voltage
reference (DACOUT) through a TTL-compatible 5-bit
digital-to-analog converter. The level of DACOUT also sets
the PGOOD and OVP thresholds. Table 1 specifies the
DACOUT voltage for the different combinations of
connections on the VID pins. The VID pins can be left open
for a logic 1 input, because they are internally pulled up to
+5V by a 10
μ
A (typically) current source. Changing the VID
inputs during operation is not recommended. The sudden
change in the resulting reference voltage could toggle the
PGOOD signal and exercise the over-voltage protection.
All VID pin combinations resulting in an INHIBIT disable the
IC and the open-collector at the PGOOD pin.
Application Guidelines
Soft-Start Interval
Initially, the soft-start function clamps the error amplifier’s
output of the PWM converter. After the output voltage
increases to approximately 80% of the set value, the
reference input of the error amplifier is clamped to a voltage
proportional to the SS pin voltage. Both linear outputs follow
a similar start-up sequence. The resulting output voltage
sequence is shown in Figure 6.
The soft-start function controls the output voltage rate of rise
to limit the current surge at start-up. The soft-start interval is
programmed by the soft-start capacitor, C
SS
. Programming
a faster soft-start interval increases the peak surge current.
The peak surge current occurs during the initial output
voltage rise to 80% of the set value.
Shutdown
The PWM output does not switch until the soft-start voltage
(V
SS
) exceeds the oscillator’s valley voltage. Additionally,
the reference on each linear’s amplifier is clamped to the
soft-start voltage. Holding the SS pin low with an open drain
or collector signal turns off all three regulators.
The VID codes resulting in an INHIBIT as shown in Table 1
also shuts down the IC.
Layout Considerations
MOSFETs switch very fast and efficiently. The speed with
which the current transitions from one device to another
causes voltage spikes across the interconnecting
impedances and parasitic circuit elements. The voltage
spikes can degrade efficiency, radiate noise into the circuit,
and lead to device over-voltage stress. Careful component
UGATE
OCSET
PHASE
OVER-
CURRENT1
+
-
GATE
CONTROL
VCC
OC1
200
μ
A
V
DS
i
D
V
SET
R
OCSET
V
IN
= +5V
OVER-CURRENT TRIP: V
DS
> V
SET
(i
D
x r
DS
(ON) > I
OCSET
R
OCSET
)
I
OCSET
+
+
FIGURE 9. OVER-CURRENT DETECTION
PWM
V
PHASE
= V
IN
- V
DS
V
OCSET
= V
IN
- V
SET
DRIVE
HIP6017
VCC
LGATE
PGND
TABLE 1. V
OUT1
VOLTAGE PROGRAM
PIN NAME
NOMINAL
OUT1
VOLTAGE
DACOUT
VID4
VID3
VID2
VID1
VID0
0
1
X
X
X
INHIBIT
0
0
1
1
X
INHIBIT
0
0
1
0
1
1.80
0
0
1
0
0
1.85
0
0
0
1
1
1.90
0
0
0
1
0
1.95
0
0
0
0
1
2.00
0
0
0
0
0
2.05
1
1
1
1
1
INHIBIT
1
1
1
1
0
2.1
1
1
1
0
1
2.2
1
1
1
0
0
2.3
1
1
0
1
1
2.4
1
1
0
1
0
2.5
1
1
0
0
1
2.6
1
1
0
0
0
2.7
1
0
1
1
1
2.8
1
0
1
1
0
2.9
1
0
1
0
1
3.0
1
0
1
0
0
3.1
1
0
0
1
1
3.2
1
0
0
1
0
3.3
1
0
0
0
1
3.4
1
0
0
0
0
3.5
NOTE: 0 = connected to GND or V
SS
, 1 = open or connected to 5V
through pull-up resistors, X = don’t care
HIP6017
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