参数资料
| 型号： | ISL1801IVZ |
| 厂商： | Intersil |
| 文件页数： | 16/29页 |
| 文件大小： | 0K |
| 描述： | IC CONV SOLAR PWR 48TSSOP |
| 标准包装： | 390 |
| 应用： | 转换器，太阳能 |
| 输入电压： | 9 V ~ 90 V |
| 输出数： | 4 |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 48-TFSOP（0.240"，6.10mm 宽） |
| 供应商设备封装： | 48-TSSOP |
| 包装： | 管件 |
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ISL1801
F SW1 ≈ -----------------------------------------
? R ON1
– 11 (EQ. 3)
? R ON2
1.05e
t ON2 = ---------------------------------------------
Detailed Operation
Dual Synchronous Buck Switching
Regulators With Constant On-Time Control
There are two synchronous Buck switching regulators in the
ISL1801. The high voltage switching regulator, VR1, can be
connected to a power source up to 90V. The low voltage
switching regulator, VR2, supports input voltages up to 14V.
Typically, VR2 is connected to the output of VR1. Both switching
regulators include integrated MOSFETs.
Both VR1 and VR2 employ a constant on-time PWM control
architecture with input voltage feed-forward. The constant
on-time PWM control architecture relies on the output ripple
voltage to provide the PWM ramp signal; thus the output filter
capacitor's ESR acts as a current-feedback resistor. For some
When V IN1 is much larger than 1V, the switching frequency of
VR1 is almost independent of its input voltage:
V OUT1
2.7e
For a 10V output the switching frequency of VR1 is about 370kHz
with R ON1 = 1M ? .
For low voltage VR2, the TON2 pin is tied to an internal 0.5V
reference and the width of the ON-time one shot is:
– 11
(EQ. 4)
V IN2 – 0.5
V IN2 is the input voltage for VR2, while R ON2 is the resistor from
V IN2 to the TON2 pin.
? R ON2 ? V IN2
applications with ceramic capacitors, the output voltage ripple is
small due to very low ESR. In order to achieve the stable
operation for very low voltage ripple applications, one internal
ramp is generated and add to the FB signal to emulate the
output voltage ripple. The high-side switch ON time is determined
The switching frequency of VR2 is:
V OUT2 ? ( V IN2 – 0.5 )
– 11
F SW2 = --------------------------------------------------------------
1.05e
(EQ. 5)
by a one-shot whose period is inversely proportional to input
voltage and directly proportional to output voltage. Another one-
When V IN2 is much larger than 0.5V, the switching frequency of
VR2 is almost independent of its input voltage:
F SW2 ≈ ---------------------------------------------
? R ON2
1.05e
shot sets a minimum OFF time (300ns typical for VR1 and 150ns
typical for VR2). The ON time one-shot triggers when the
following conditions are met: the error comparator's output is
V OUT2
– 11
(EQ. 6)
high, the synchronous rectifier current is below the current-limit
threshold, and the minimum OFF time one-shot has timed out.
The controller utilizes the valley point of the output ripple to
regulate and determine the OFF time.
SWITCHING FREQUENCY OF VR1 AND VR2
Each PWM core includes a one-shot that sets the ON time for the
high-side switch of each voltage regulator. Each fast, low-jitter,
adjustable one-shot includes circuitry that varies the ON time in
response to the input voltage and output voltage. This algorithm
results in a nearly constant switching frequency despite the lack
of a fixed-frequency clock generator.
The high-side switch ON time is inversely proportional to the
input voltage as measured by the TON1 and TON2 pins for VR1
and VR2 respectively. Both TON1 and TON2 pins are tied to an
internal voltage reference and the current flowing into these pins
is monitored to generate the ON time one shot.
For a 3.3V output the switching frequency of VR2 is about
314kHz with R ON2 = 1M ? .
CURRENT LIMITING OF VR1 AND VR2
To prevent the output current from becoming too high a new
ON-time pulse can start only when the current through the
synchronous MOSFET is below the current limiting threshold. This
limits the valley of the output inductor current to a fixed value,
typically 140mA for VR1 and 200mA for VR2.
The maximum peak current through the output inductor is the
sum of the current limiting threshold and the current ripple
determined by the ON-time, inductor value and the input/output
voltage.
DIODE EMULATION OPERATION
To improve the efficiency for light loads, the synchronous
? R ON1
2.7e
t ON1 = -----------------------------------------
For high voltage VR1 the TON1 pin is tied to an internal 1V
reference and the width of the ON-time one shot is:
– 11
V IN1 – 1
(EQ. 1)
MOSFET is turned off when its current drops to 0. This prevents
negative current through the output inductor emulating diode
operation.
With diode emulation operation under light load conditions the
output voltage may drop slowly after the synchronous MOSFET
V IN1 is the input voltage for high voltage VR1, while R ON1 is the
resistor from V IN1 to the TON1 pin.
The switching frequency of VR1 is:
turns OFF. It may take a long time for the output voltage to drop
below the reference voltage to start a new switching cycle. This
will have the effect of reducing the switching frequency under
light load conditions.
? R ON1 ? V IN1
V OUT1 ? ( V IN1 – 1 )
– 11
F SW1 = -----------------------------------------------------------
2.7e
16
(EQ. 2)
OVERVOLTAGE PROTECTION
The feedback voltage for VR1 and VR2 is continuously monitored
to prevent the output voltage from going too high.
When the VR1 output voltage feedback FB1 is higher than 120%
of VREF1, the Overvoltage Protection (OVP) is triggered. When
this condition occurs, the lower side MOSFET of VR1 is turned on
FN8259.0
June 29, 2012
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| ISL1801IVZ-T | 功能描述:IC CONV SOLAR PWR 48TSSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - 专用型 系列:- 标准包装:43 系列:- 应用:控制器，Intel VR11 输入电压:5 V ~ 12 V 输出数:1 输出电压:0.5 V ~ 1.6 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:48-VFQFN 裸露焊盘 供应商设备封装:48-QFN（7x7） 包装:管件 |
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