- 您现在的位置：买卖IC网 > PDF目录15221 > SG1577SZ (Fairchild Semiconductor)IC REG CTRLR BST PWM VM 20-SOP PDF资料下载
参数资料
| 型号： | SG1577SZ |
| 厂商： | Fairchild Semiconductor |
| 文件页数： | 10/14页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BST PWM VM 20-SOP |
| 标准包装： | 1 |
| PWM 型： | 电压模式 |
| 输出数： | 2 |
| 频率 - 最大： | 352kHz |
| 占空比： | 95% |
| 电源电压： | 8 V ~ 15 V |
| 降压： | 是 |
| 升压： | 是 |
| 回扫： | 无 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 无 |
| 工作温度： | -40°C ~ 85°C |
| 封装/外壳： | 20-SOIC（0.295"，7.50mm 宽） |
| 包装： | 标准包装 |
| 产品目录页面： | 1222 (CN2011-ZH PDF) |
| 其它名称： | SG1577SZDKR |
Functional Description
The SG1577 is a dual-channel voltage-mode PWM
controller. It has two sets of synchronous MOSFET
driving circuits. The two channels are running 180-
degrees out of phase. The following descriptions
highlight the advantages of the SG1577 design.
Prevent CLN Noise in SG1577
To prevent noise/spike on CLN from affecting OCP
judgment, SG1577 internal has a 500 ns blanking time
to filter out this noise/spike on CLN at each turn-on
cycle and counts for eight cycles of CLP>CLN, then
OCP is asserted.
Soft-Start
An internal startup current (10 μA) flows out of SS/EN
pin to charge an external capacitor. During the startup
sequence, SG1577 isn’t enabled until the SS/ENB pin is
higher than 1.2 V. From 1.2 V to (1.2 + 1.6 x D ON /
D ON_MAX ) V , PWM duty cycle gradually increases
following SS/ENB pin voltage to bring output rising. After
(1.2 + 1.6 x D ON / D ON_MAX ) V, the soft-start period ends
and SS/ENB pin continually goes up to 4.8 V. When
input power is abnormal, the external capacitor on SS
pin is shorted to ground and the chip is disabled.
240
220
200
180
160
140
120
100
80
60
40
20
V OFFSET of OCP Comparator
T SOFTSTART = C SS/ENB x 1.6 x D ON / D ON_MAX / I SOURCE
(1)
0
4
6
8
10
12
14
16
VCC (V)
Over-Current Protection (OCP)
Over-current protection is implemented by sensing the
voltage drop across the drain and the source of
external high-side MOSFET. Over-current protection is
triggered when the voltage drop on external high-side
MOSFET’s R DS(ON) is greater than the programmable
current limit voltage threshold. 120 μA flowing through
an external resistor between input voltage and the CLP
pin sets the threshold of current limit voltage. When
over-current condition is true, the system is protected
against the cycle-by-cycle current limit. A counter
counts a series of over-current peak values to eight
cycles; the soft-start capacitor is discharged by a 1 μA
current until the voltage on SS pin reaches 1.2 V.
During the discharge period, the high-side driver is
turned off and the low-side driver is turned on. Once
the voltage on SS/ENB pin is under 1.2 V, the normal
soft-start sequence is initiated and the 10 μA current
charges the soft-start capacitor again.
Figure 23. V OFFSET1/2 vs. VCC
Error Amplifier
The IN1 and IN2 pins are connected to the
corresponding internal error amplifier’s inverting input
and the outputs of the error amplifiers are connected to
the corresponding COMP1 and COMP2 pins. The
COMP1 and COMP2 pins are available for control-loop
compensation externally. Non-inverting inputs are
internally tied to a fixed 0.7 V ±1.5% reference voltage.
Oscillator Operation
The SG1577 has a frequency-programmable oscillator.
The oscillator is running at 60 kHz when the RT pin is
floating. The oscillator frequency can be adjusted from
60 kHz up to 320 kHz by an external resistor R RT
between RT pin and the ground. The oscillator
generates a sawtooth wave that has 90% rising duty.
I L(OCP) = [(R SENSE x I OCSET + V OFFSET ) / R DS(ON) -
(V IN - V OUT ) x V OUT / (f OSC x L OUT x V IN x 2) ]
(2)
Sawtooth wave voltage threshold is from 1.2 V to 2.8 V.
The frequency of oscillator can be programmed by the
following equation:
where, V OFFSET (=10 mV) is the offset voltage
contributed by the internal OCP comparator.
f OSC , RT(kHz) = 60kHz + 8522 / R RT (k ? )
(3)
Design Notes
V CC noise/spike affects the offset voltage of the OCP
comparator Figure 23 shows the V OFFSET1/2 vs. V CC
variation curve, which is a simulation result by IC
internal circuitry. Calculate the OCP variation between
V CC =12 V and V CC =4 V. For Ch1 or Ch2, V OFFSET /
R DS(ON) = 172 mV / 9 m ? = 19 A is affected. V CC >10 V is
the recommended range; lower, and the comparator’s
offset voltage is large.
? 2009 Fairchild Semiconductor Corporation
SG1577 ? Rev. 1.0.6
10
Output Driver
The high-side gate drivers need an external
bootstrapping circuit to provide the required boost
voltage. The highest gate driver’s output (15 V is the
allowed) on high-side and low-side MOSFETs forces
external MOSFETs to have the lowest R DS(ON) , which
results in higher efficiency.
Over-Temperature Protection (OTP)
The device is over-temperature protected. When chip
temperature is over 150 ° C, the chip enters tri-state
(high-side driver is turned off). The hysteresis is 20 ° C.
www.fairchildsemi.com
相关PDF资料 |
PDF描述 |
|---|---|
| EYM22DTBS | CONN EDGECARD 44POS R/A .156 SLD |
| EBM25DTAT | CONN EDGECARD 50POS R/A .156 SLD |
| UPB2C680MHD | CAP ALUM 68UF 160V 20% RADIAL |
| EYM22DTAS | CONN EDGECARD 44POS R/A .156 SLD |
| EEM40DTAN | CONN EDGECARD 80POS R/A .156 SLD |
相关代理商/技术参数 |
参数描述 |
|---|---|
| SG15A | 制造商:BILIN 制造商全称:Galaxy Semi-Conductor Holdings Limited 功能描述:FAST RECOVERY RECTIFIERS |
| SG15B | 制造商:BILIN 制造商全称:Galaxy Semi-Conductor Holdings Limited 功能描述:FAST RECOVERY RECTIFIERS |
| SG15D | 制造商:BILIN 制造商全称:Galaxy Semi-Conductor Holdings Limited 功能描述:FAST RECOVERY RECTIFIERS |
| SG15G | 制造商:BILIN 制造商全称:Galaxy Semi-Conductor Holdings Limited 功能描述:FAST RECOVERY RECTIFIERS |
| SG15J | 制造商:BILIN 制造商全称:Galaxy Semi-Conductor Holdings Limited 功能描述:FAST RECOVERY RECTIFIERS |
发布紧急采购，3分钟左右您将得到回复。