|Category||Analog & Mixed-Signal Processing => Power|
|Description||Fixed Output Buck Controller|
|Datasheet||Download ADP3156-1.5 datasheet
FEATURES Active Voltage Positioning with Gain and Offset Adjustment Optimal Compensation for Superior Load Transient Response Fixed 1.8 V and 2.5 V Output Versions Dual N-Channel Synchronous Driver On-Board Linear Regulator Controller Total Output Accuracy 1% Over Temperature High Efficiency, Current-Mode Operation Short Circuit Protection Overvoltage Protection Crowbar Protects Loads with No Additional External Components Power Good Output SO-16 Package APPLICATIONS Desktop Computer Supplies ACPI-Compliant Power Systems General Purpose DC-DC Converters GENERAL DESCRIPTIONDual Power Supply Controller for Desktop Systems ADP3156
DELAY NONOVERLAP DRIVE VREF +15% 2R CROWBAR IN OFF CMPI R gm VREF REFERENCE VLDO 1.20V FB OFF-TIME CONTROL VIN SENSE R VT1 VREF +5% VREF 5%
The is a highly efficient synchronous buck switching regulator controller optimized for converting the 5 V main supply into lower supply voltages required on the motherboards of Pentium® III and other high performance processor systems. The ADP3156 uses a current mode, constant off-time architecture to drive two external N-channel MOSFETs at a programmable switching frequency that can be optimized for size and efficiency. It also uses a unique supplemental regulation technique called active voltage positioning to enhance load transient performance. Active voltage positioning results in a DC/DC converter that provides the best possible transient response using the minimum number of output capacitors and smallest footprint. Unlike voltage-mode and standard currentmode architectures, active voltage positioning adjusts the output voltage as a function of the load current so that it is always optimally positioned for a system transient. The ADP3156 provides accurate and reliable short circuit protection and adjustable current limiting. It also includes an integrated overvoltage crowbar function to protect the microprocessor from destruction in case the core supply exceeds the nominal programmed voltage by more than 15%.
The ADP3156 contains a linear regulator controller that is designed to drive an external N-channel MOSFET. This linear regulator is used to generate the auxiliary voltages (AGP, GTL, etc.) required in most motherboard designs, and has been designed to provide a high bandwidth load-transient response. A pair of external feedback resistors sets the linear regulator output voltage.
Pentium is a registered trademark of Intel Corporation. All other trademarks are the property of their respective holders.
Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781/329-4700 World Wide Web Site: http://www.analog.com Fax: 781/326-8703 © Analog Devices, Inc., 1999
Parameter OUTPUT ACCURACY ADP3156-2.5 V OUTPUT VOLTAGE LINE REGULATION INPUT DC SUPPLY CURRENT2 Normal Mode Shutdown CURRENT SENSE THRESHOLD VOLTAGE CT PIN DISCHARGE CURRENT
ILOAD 10 A (Figure 2) VIN 5.25 V VSD = +25°C, VSD 2.0 V VSENSE Forced to VOUT = +25°C VOUT in Regulation VOUT +25°C % Above Output Voltage % Below Output Voltage
OFF-TIME DRIVER OUTPUT TRANSITION TIME POSITIVE POWER GOOD TRIP POINT3 NEGATIVE POWER GOOD TRIP POINT3 POWER GOOD RESPONSE TIME CROWBAR TRIP POINT ERROR AMPLIFIER OUTPUT IMPEDANCE ERROR AMPLIFIER TRANSCONDUCTANCE ERROR AMPLIFIER MINIMUM OUTPUT VOLTAGE ERROR AMPLIFIER MAXIMUM OUTPUT VOLTAGE ERROR AMPLIFIER BANDWIDTH 3 dB LINEAR REGULATOR FEEDBACK CURRENT LINEAR REGULATOR OUTPUT VOLTAGE SHUTDOWN (SD) PIN Low Threshold High Threshold Input CurrenttOFF , tF VPWRGD tPWRGD VCROWBAR ROERR gm(ERR) VCMPMIN VCMPMAX BWERR IFB VO2
VSENSE Forced to VOUT + 3% VSENSE Forced to VOUT 3% CMP = Open
Figure 2, VLDOIN 1.8 V RPROG 1 A Part Active Part in Shutdown
NOTES 1 All limits at temperature extremes are guaranteed via correlation using standard Statistical Quality Control (SQC) methods. Specifications subject to change without notice. 2 Dynamic supply current is higher due to the gate charge being delivered to the external MOSFETs. 3 The trip point is for the output voltage coming into regulation. Specifications subject to change without notice.Mnemonic NC AGND SD FB VLDO SENSE SENSE+ CT CMP PWRGD VCC DRIVE2 DRIVE1 PGND
Function No Connect. Analog Ground. All internal signals of the ADP3156 are referenced to this ground. Shutdown. A logic high will place the ADP3156 in shutdown and disable both outputs. This pin is internally pulled down. Feedback connection for the linear controller. Connect this pin to the resistor divider network to set the output voltage of the linear regulator. Gate Drive for the linear regulator N-channel MOSFET. Connects to the internal resistor divider that senses the output voltage. This pin is also the reference input for the current comparator. input for the current comparator. The output current is sensed as a voltage at this pin with respect to SENSE. External Capacitor CT connection to ground sets the off-time of the device. Error Amplifier output and compensation point. The voltage at this output programs the output current control level between the SENSE pins. Power Good. An open drain signal indicates the output voltage is within ± 5% regulation band. Supply Voltage to ADP3156. Gate Drive for the (bottom) Synchronous Rectifier N-channel MOSFET. The voltage at DRIVE2 swings from ground to VCC. Gate Drive for the buck switch N-channel MOSFET. The voltage at DRIVE1 swings from ground to VCC. Power Ground. The drivers turn off the buck and synchronous MOSFETs by discharging their gate capacitances to this pin. PGND should have a low impedance path to the source of the synchronous MOSFET.
Input Supply Voltage (VCC). +16 V Shutdown Input Voltage. +16 V Operating Ambient Temperature Range. to +70°C Junction Temperature Range. to +150°C JA. 90°C/W Storage Temperature Range. to +150°C Lead Temperature (Soldering, 10 sec). +300°C
*This is a stress rating only; operation beyond these limits can cause the device to be permanently damaged.
CAUTION ESD (electrostatic discharge) sensitive device. Electrostatic charges as high 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although the ADP3156 features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality.
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