Preliminary Datasheet ADP1074 (Analog Devices) - 10

ADP1074 Preliminary Technical Data PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
Figure 3. Pin Configuration
Table 6. Pin Function Descriptions Pin No. Mnemonic Description
1 NGATE Driver output for main power MOSFET on the primary side. Multiple function pin. Connect a resistor from NGATE to PGND1 to setup the predetermined dead time between PGATE and SR2. 2 PGATE Driver for the active clamp MOSFET of the forward topology. This pin is referenced to PGND1. 3 PGND1 Power ground on primary side. Star connect this pin to AGND1. 4 AGND1 Analog ground on primary. Star connect this pin to PGND1. Use this pin to differentially sense the primary current sensed with the sense resistor between the CS and AGND1 pins. 5 VREG1 8 V output for MOSFET drivers. Connect 1uF or greater at this pin. It is recommended to not put an external load on this pin in any way. This pin is referenced to PGND1. 6 VIN Input voltage. Connect a 4.7µF capacitor at this pin. The size of this capacitor can be reduced if the input voltage to this pin is guaranteed to be stable. This pin is referenced to PGND1. 7 EN Precision enable input. The controller is enabled when the voltage at EN pin is above the EN threshold voltage. Soft stop is enabled when EN drops below the EN threshold voltage. This pin also has a programmable EN hysteresis. This pin is referenced to AGND1. 8 CS Input current sensing. This pin senses the input pulse width modulated current. Place a current sense resistor between the source terminal of the power MOSFET and PGND1. This current sense resistor sets up the input current limit. This pin is also used for external slope compensator. Connect a resistor from CS to the current sense resistor to generate a voltage ramp for the slope compensation. This pin is referenced to AGND1. It is recommended to connect a 33-100pF capacitor at this pin which acts as an RC filter along with the slope compensation resistor. 9 RT Connect two resistors in series that sum up to the appropriate resistor from RT to AGND1 to set the switching frequency. Also see DMAX pin. See RT and duty cycle section for formula. 10 SYNC Connect an external clock to the SYNC pin to synchronize the internal oscillator to this external clock frequency. Connect SYNC to AGND1 if this feature is not used. It is recommended that the SYNC frequency be within 10% of the frequency set by the RT pin. 11 SS1 Connect a capacitor at this pin to set up the open loop soft start time. This pin is referenced to AGND1. 12 DMAX Maximum duty cycle control. Connect DMAX to the center tap of the resistor divider at the RT pin to setup the maximum duty cycle. See RT and duty cycle section for formula. 13 MODE Light load mode setting. Connect MODE to AGND2 to disable discontinuous conduction mode (DCM) operation, or to a high logic (2.5 V or higher such as VREG2 pin) to force a LLM operation, or to a resistor to setup a fixed light load mode (LLM) threshold voltage. 14 PGOOD Power Good bar. Open drain output. Connect a pull-up resistor from PGOOD to VREG2. 15 SS2 Soft start on secondary. Connect a capacitor from SS2 to AGND2 to setup the soft start time on the secondary. 16 COMP Compensation node on the secondary. This pin is the output of the gm amplifier. This pin is referenced to AGND2. Rev. PrB | Page 10 of 14 Document Outline FEATURES APPLICATIONS GENERAL DESCRIPTION TABLE OF CONTENTS TYPICAL APPLICATION CIRCUITS SPECIFICATIONS REGULATORY INFORMATION ABSOLUTE MAXIMUM RATINGS THERMAL RESISTANCE ESD CAUTION PIN CONFIGURATION AND FUNCTION DESCRIPTIONS SIMPLIFIED BLOCK DIAGRAM APPLICATIONS INFORMATION INSULATION LIFETIME OUTLINE DIMENSIONS