- 您现在的位置：买卖IC网 > PDF目录1841 > MAX1856EUB (Maxim Integrated Products)IC PS PWM SLIC SYNCH 10-UMAX PDF资料下载
参数资料
| 型号： | MAX1856EUB |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 11/18页 |
| 文件大小： | 0K |
| 描述： | IC PS PWM SLIC SYNCH 10-UMAX |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 50 |
| 应用： | 控制器，卫星接收机顶盒，xDSL 和线缆调制解调器 |
| 输入电压： | 3 V ~ 28 V |
| 输出数： | 1 |
| 输出电压： | -24V，-72V |
| 工作温度： | 0°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 10-TFSOP，10-MSOP（0.118"，3.00mm 宽） |
| 供应商设备封装： | 10-uMAX |
| 包装： | 管件 |
Wide Input Range, Synchronizable,
PWM SLIC Power Supply
100kHz to 500kHz frequency, which is set by a resistor
(R OSC ) connected from FREQ to GND. The relationship
between f OSC and R OSC is:
between 200μA and 250μA as shown in Figure 1. To
ensure that the MAX1856 regulates both outputs with
the same degree of accuracy over load, select the
R OSC =
50M ? × kHz
? OSC ( kHz )
feedback resistors (R1 and R2) so their current ratio
(I R1 :I R2 ) equals the output power ratio (P OUT1 :P OUT2 )
under full load:
Thus, a 250kHz operating frequency, for example, is
set with R OSC = 200k ? . At higher frequencies, the
I R 1
I R 2
=
V OUT 1 I OUT 1
V OUT 2 I OUT 2
I R 1 = OUT 1 and I R 2 = OUT 2
magnetic components will be smaller. Peak currents
and, consequently, resistive losses will be lower at the
higher switching frequency. However, core losses, gate
charge currents, and switching losses increase with
higher switching frequencies.
Rising clock edges on SYNC/ SHDN are interpreted as
synchronization input. If the sync signal is lost while
SYNC/ SHDN is high, the internal oscillator takes over at
the end of the last cycle, and the frequency is returned
to the rate set by R OSC . If the signal is lost with
SYNC/ SHDN low, the IC waits for 50μs before shutting
down. This maintains output regulation even with inter-
mittent sync signals. When an external sync signal is
used, Idle Mode switchover at the 15mV current-sense
threshold is disabled so that Idle Mode only occurs at
very light loads. Also, R OSC should be set for a fre-
quency 15% below the SYNC clock rate:
Once R3 and the dual feedback currents (I R1 and I R2 )
are determined from the two equations above, use the
following two equations to determine R1 and R2:
V V
R 1 R 2
Selecting the Transformer
The MAX1856 PWM controller works with economical
off-the-shelf transformers. The transformer selection
depends on the input-to-output voltage ratio, output
current capacity, duty cycle, and oscillator frequency.
Table 1 shows recommended transformers for the typi-
cal applications, and Table 2 gives some recommend-
ed suppliers.
Transformer Turns Ratio
R OSC ( SYNC ) =
50 M ? × kHz
0 . 85 ? OSC ( kHz )
The transformer turns ratio is a function of the input-to-
output voltage ratio and maximum duty cycle. Under
steady-state conditions, the change in flux density dur-
Setting the Output Voltage
Set the output voltage using two external resistors form-
ing the on-time must equal the return change in flux
density during the off-time (or flyback period):
= OUT OFF
ing a resistive divider to FB between the output and
REF. First select a value for R3 between 3.3k ? and
100k ? . R1 is then given by:
V IN t ON
N P
V t
N S
R 1 = R 3 ? OUT ?
? V ?
? V REF ?
For a dual output as shown in Figure 1, a split feedback
technique is recommended. Since the feedback volt-
age threshold is 0, the total feedback current is:
For example, selecting a 50% duty cycle for the stan-
dard application circuit (Figure 1) and a +12V input
voltage, the -72V output requires a 1:6 turns ratio, and
the -24V output requires a 1:2 turns ratio. Therefore, a
transformer with a 1:2:2:2 turns ratio was selected.
Primary inductance
The average input current at maximum load can be cal-
I TOTAL = I R 1 + I R 2 = REF
V
R 3
Since the feedback resistors are connected to the ref-
culated as:
I IN ( DC ) =
V OUT I OUT ( MAX )
η V IN ( MIN )
erence, I TOTAL must be <400μA so that V REF is guaran-
teed to be in regulation (see Electrical Characteristics
Table ). Therefore, select R3 so the total current value is
where η = efficiency. For V OUT = -24V, I OUT(MAX) =
400mA, and V IN(MIN) = 10.8V as shown in Figure 1, this
______________________________________________________________________________________
11
相关PDF资料 |
PDF描述 |
|---|---|
| MAX1857EUA47+ | IC REG LDO 4.75V/ADJ .5A 8-UMAX |
| MAX1858EEG+T | IC REG CTRLR BUCK PWM VM 24-QSOP |
| MAX1865TEEP+T | IC PWR SUPPLY CONTROLLER 20QSOP |
| MAX1873REEE+T | IC CNTRLR CHARGE LI+ 16-QSOP |
| MAX1874ETE+ | IC LI+ CHARGER DUAL-IN 16-TQFN |
相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1856EUB+ | 功能描述:电信线路管理 IC Synchronizable PWM SLIC Power Supply RoHS:否 制造商:STMicroelectronics 产品:PHY 接口类型:UART 电源电压-最大:18 V 电源电压-最小:8 V 电源电流:30 mA 最大工作温度:+ 85 C 最小工作温度:- 40 C 安装风格:SMD/SMT 封装 / 箱体:VFQFPN-48 封装:Tray |
| MAX1856EUB+T | 功能描述:电信线路管理 IC Synchronizable PWM SLIC Power Supply RoHS:否 制造商:STMicroelectronics 产品:PHY 接口类型:UART 电源电压-最大:18 V 电源电压-最小:8 V 电源电流:30 mA 最大工作温度:+ 85 C 最小工作温度:- 40 C 安装风格:SMD/SMT 封装 / 箱体:VFQFPN-48 封装:Tray |
| MAX1856EUB-T | 功能描述:电信线路管理 IC RoHS:否 制造商:STMicroelectronics 产品:PHY 接口类型:UART 电源电压-最大:18 V 电源电压-最小:8 V 电源电流:30 mA 最大工作温度:+ 85 C 最小工作温度:- 40 C 安装风格:SMD/SMT 封装 / 箱体:VFQFPN-48 封装:Tray |
| MAX1856EVKIT | 功能描述:电源管理IC开发工具 Evaluation Kit for the MAX1856 RoHS:否 制造商:Maxim Integrated 产品:Evaluation Kits 类型:Battery Management 工具用于评估:MAX17710GB 输入电压: 输出电压:1.8 V |
| MAX1857EUA47 | 功能描述:低压差稳压器 - LDO 500mA Ripple-Rejecting RoHS:否 制造商:Texas Instruments 最大输入电压:36 V 输出电压:1.4 V to 20.5 V 回动电压（最大值）:307 mV 输出电流:1 A 负载调节:0.3 % 输出端数量: 输出类型:Fixed 最大工作温度:+ 125 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-20 |
发布紧急采购，3分钟左右您将得到回复。