- 您现在的位置：买卖IC网 > PDF目录296253 > ISL6426CB (INTERSIL CORP) Triple 3-Input Positive-NAND Gates 14-SOIC -40 to 85 PDF资料下载
参数资料
| 型号： | ISL6426CB |
| 厂商： | INTERSIL CORP |
| 元件分类： | 稳压器 |
| 英文描述： | Triple 3-Input Positive-NAND Gates 14-SOIC -40 to 85 |
| 中文描述： | SWITCHING CONTROLLER, 770 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封装： | PLASTIC, MS-012-AC, SOIC-16 |
| 文件页数： | 5/18页 |
| 文件大小： | 541K |
| 代理商： | ISL6426CB |
13
One of the parameters limiting the converter’s response to
a load transient is the time required to change the inductor
current. Given a sufficiently fast control loop design, the
ISL6406, ISL6426 will provide either 0% or 100% duty
cycle in response to a load transient. The response time is
the time required to slew the inductor current from an initial
current value to the transient current level. During this
interval the difference between the inductor current and the
transient current level must be supplied by the output
capacitor. Minimizing the response time can minimize the
output capacitance required.
The response time to a transient is different for the
application of load and the removal of load. The following
equations give the approximate response time interval for
application and removal of a transient load:
where: ITRAN is the transient load current step, tRISE is the
response time to the application of load, and tFALL is the
response time to the removal of load. The worst case
response time can be either at the application or removal of
load. Be sure to check both of these equations at the
minimum and maximum output levels for the worst case
response time.
Input Capacitor Selection
Use a mix of input bypass capacitors to control the voltage
overshoot across the MOSFETs. Use small ceramic
capacitors for high frequency decoupling and bulk capacitors
to supply the current needed each time Q1 turns on. Place the
small ceramic capacitors physically close to the MOSFETs
and between the drain of Q1 and the source of Q2.
The important parameters for the bulk input capacitor are the
voltage rating and the RMS current rating. For reliable
operation, select the bulk capacitor with voltage and current
ratings above the maximum input voltage and largest RMS
current required by the circuit. The capacitor voltage rating
should be at least 1.25 times greater than the maximum
input voltage and a voltage rating of 1.5 times is a
conservative guideline. The RMS current rating requirement
for the input capacitor of a buck regulator is approximately
1/2 the DC load current.
The maximum RMS current required by the regulator may be
closely approximated through the following equation:
For a through hole design, several electrolytic capacitors may
be needed. For surface mount designs, solid tantalum
capacitors can be used, but caution must be exercised with
regard to the capacitor surge current rating. These capacitors
must be capable of handling the surge-current at power-up.
Some capacitor series available from reputable manufacturers
are surge current tested.
MOSFET Selection/Considerations
The ISL6406, ISL6426 requires two N-Channel power
MOSFETs. These should be selected based upon rDS(ON),
gate supply requirements, and thermal management
requirements.
In high-current applications, the MOSFET power dissipation,
package selection and heatsink are the dominant design
factors. The power dissipation includes two loss components;
conduction loss and switching loss. The conduction losses are
the largest component of power dissipation for both the upper
and the lower MOSFETs. These losses are distributed between
the two MOSFETs according to duty factor.
The switching losses seen when sourcing current will be
different from the switching losses seen when sinking current.
When sourcing current, the upper MOSFET realizes most of
the switching losses. The lower switch realizes most of the
switching losses when the converter is sinking current (see
equations on next page). These equations assume linear
voltage-current transitions and do not adequately model power
loss due the reverse-recovery of the upper and lower
MOSFET’s body diode.
The gate-charge losses are dissipated by the ISL6406,
ISL6426 and don't heat the MOSFETs. However, large gate-
charge increases the switching interval, tSW which increases
the MOSFET switching losses. Ensure that both MOSFETs are
within their maximum junction temperature at high ambient
temperature by calculating the temperature rise according to
package thermal-resistance specifications. A separate heatsink
may be necessary depending upon MOSFET power, package
type, ambient temperature and air flow.
Given the reduced available gate bias voltage (5V), logic-
level or sub-logic-level transistors should be used for both N-
MOSFETs. Caution should be exercised with devices
exhibiting very low VGS(ON) characteristics. The shoot-
through protection present aboard the ISL6406, ISL6426
may be circumvented by these MOSFETs if they have large
parasitic impedances and/or capacitances that would inhibit
the gate of the MOSFET from being discharged below its
tRISE =
L x ITRAN
VIN - VOUT
tFALL =
L x ITRAN
VOUT
IRMS
MAX
VOUT
VIN
--------------
IOUT
MAX
2
1
12
------
VIN VOUT
–
Lfs
×
-----------------------------
VOUT
VIN
--------------
×
2
×
+
×
=
PLOWER = Io2 x rDS(ON) x (1 - D)
Where: D is the duty cycle = VOUT / VIN,
tSW is the combined switch ON and OFF time, and
fs is the switching frequency.
Losses while Sourcing current
Losses while Sinking current
PLOWER
Io
2
rDS ON
()
×
1D
–
()
×
1
2
--- Io
VIN
×
tSW fs
×
+
=
PUPPER
Io
2
rDS ON
()
×
D
×
1
2
--- Io
VIN
×
tSW fs
×
+
=
PUPPER = Io2 x rDS(ON) x D
ISL6406, ISL6426
相关PDF资料 |
PDF描述 |
|---|---|
| ISL6426CBZ | Single Synchronous Buck Pulse-Width Modulation (PWM) Controller |
| ISL6426CR | Single Synchronous Buck Pulse-Width Modulation (PWM) Controller |
| ISL6426CRZ | Single Synchronous Buck Pulse-Width Modulation (PWM) Controller |
| ISL6426CRZ-T | Single Synchronous Buck Pulse-Width Modulation (PWM) Controller |
| ISL6426CV | Single Synchronous Buck Pulse-Width Modulation (PWM) Controller |
相关代理商/技术参数 |
参数描述 |
|---|---|
| ISL6426CR | 制造商:Rochester Electronics LLC 功能描述:- Bulk 制造商:Intersil Corporation 功能描述: |
| ISL6426CV | 制造商:Rochester Electronics LLC 功能描述:- Bulk 制造商:Intersil Corporation 功能描述: |
| ISL6426IB | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
| ISL6426IB-T | 制造商:Rochester Electronics LLC 功能描述:- Tape and Reel |
| ISL6426IR | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
发布紧急采购，3分钟左右您将得到回复。