công cụ tìm kiếm bảng dữ liệu linh kiện điện tử |
|
ADM1051AJR bảng dữ liệu(PDF) 6 Page - Analog Devices |
|
ADM1051AJR bảng dữ liệu(HTML) 6 Page - Analog Devices |
6 / 10 page REV. 0 ADM1051/ADM1051A –6– GENERAL DESCRIPTION The ADM1051/ADM1051A are dual, precision, voltage regulator controllers intended for power rail generation and active bus ter- mination in AGP and ICH applications on personal computer motherboards. They contain a precision 1.2 V bandgap ref- erence and two almost identical channels consisting of control amplifiers driving external power devices. The main difference between the two channels is the regulated output voltage, defined by the resistor ratios on the voltage sense inputs of each channel. Channel 1 has an output of nominally 1.515 V, but can be switched to a 3.3 V output, while Channel 2 has a nominal output of 1.818 V. Channel 1 is also optimized for driving MOSFETs with lower on-resistance and higher gate capaci- tance, as explained later. Each channel has a shutdown input to turn off amplifier output and protection circuitry for the external power device. The shutdown input of Channel 1 has additional functionality as described later. The ADM1051A has some minor differences from the ADM1051 to support power-supply sequencing and voltage requirements of some I/O control hub chipsets, which dictate that the 1.818 V rail must never be more than 2 V below the 3.3 V rail. The ADM1051/ADM1051A operates from a 12 V VCC supply. The outputs are disabled until VCC climbs above the Power-On Reset threshold (6 V–9 V). POR does not apply to Channel 2 of the ADM1051A. This output will begin to rise as soon as there is sufficient gate drive to turn on the external MOSFET. The outputs from the ADM1051/ADM1051A are used to drive external N-channel MOSFETs, operating as source-followers. This has the advantage that N-channel devices are cheaper than P-channel devices of similar performance, and the circuit is easier to stabilize than one using P-channel devices in a common- source configuration. The external power devices are protected by a “Hiccup Mode” circuit that operates if the circuit goes out of regulation due to an output short-circuit. In this case the power device is pulsed on/off with a 1:40 duty-cycle to limit the power dissipation until the fault condition is removed. Again, to prevent Channel 2 falling more than 2 V below Channel 1, Hiccup Mode does not operate on Channel 2 of the ADM1051A. CIRCUIT DESCRIPTION CONTROL AMPLIFIERS The reference voltage is amplified and buffered by the control amplifiers and external MOSFETs, the output voltage of each channel being determined by the feedback resistor network between the sense input and the inverting input of the control amplifier. The two control amplifiers in the ADM1051/ADM1051A are almost identical, apart, from the ratios of the feedback resistor networks on the sense inputs. A power-on reset circuit disables the amplifier output until VCC has risen above the reset thresh- old (not Channel 2 of ADM1051A). Each amplifier output drives the gate of an N-channel power MOSFET, whose drain is connected to the unregulated supply input and whose source is the regulated output voltage, which is also fed back to the appropriate sense input of the ADM1051/ ADM1051A. The control amplifiers have high current-drive capability so they can quickly charge and discharge the gate capacitance of the external MOSFET, thus giving good transient response to changes in load or input voltage. In particular, Channel 1 is optimized to drive MOSFETs with very low on resistance and correspondingly higher gate capacitance such as the PHD55N03LT from Philips. This is to minimize voltage drop across the MOSFET when Channel 1 is used in 3.3 V mode, as explained later. SHUTDOWN INPUTS AND TYPEDET COMPATIBILITY Each channel has a separate shutdown input, which may be controlled by a logic signal, and allows the output of the regula- tor to be turned on or off. If the shutdown input is held high or not connected, the regulator operates normally. If the shutdown input is held low, the enable input of the control amplifier is turned off and the amplifier output goes low, turning off the regulator. The SHDN1 input on Channel 1 has additional functionality that can be controlled by the TYPEDET signal on PC motherboards. The AGP bus on a PC motherboard can have two different modes of operation, requiring different regulated voltages of 3.3 V or 1.5 V. These two modes are signaled by the TYPEDET signal on the PC motherboard, as follows: TYPEDET = 0 V – Regulated Voltage 1.5 V (4 × AGP Graphics) TYPEDET Floating – Regulated Voltage 3.3 V (2 × AGP Graphics) 5VSB – V 1.855 1.555 3.7 3.9 4.1 4.7 1.805 1.755 1.655 1.455 1.605 5.3 1.505 1.705 1.405 1.355 1.305 4.3 4.5 4.9 5.1 25 C VCH2 V's 5VSB ILOAD 500m 70 C 0 C TPC 13. ADM1051A Channel 2 Output Voltage vs. 5 VSB Voltage. Test Circuit as Figure 7, ILOAD = 500 mA 5VSB – V 1.855 1.555 3.7 3.9 4.1 4.7 1.805 1.755 1.655 1.455 1.605 5.3 1.505 1.705 1.405 1.355 1.305 4.3 4.5 4.9 5.1 25 C 0 C 70 C VCH2 V's 5VSB ILOAD 1 TPC 14. ADM1051A Channel 2 Output Voltage vs. 5 VSB Voltage. Test Circuit as Figure 7, ILOAD = 1 A |
Số phần tương tự - ADM1051AJR |
|
Mô tả tương tự - ADM1051AJR |
|
|
Link URL |
Chính sách bảo mật |
ALLDATASHEET.VN |
Cho đến nay ALLDATASHEET có giúp ích cho doanh nghiệp của bạn hay không? [ DONATE ] |
Alldatasheet là | Quảng cáo | Liên lạc với chúng tôi | Chính sách bảo mật | Trao đổi link | Tìm kiếm theo nhà sản xuất All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |