Datasheet LTM8027 (Analog Devices) - 9

LTM8027
PIN FUNCTIONS PACKAGE ROW AND COLUMN LABELING MAY VARY GND (Bank 2):
Tie these GND pins to a local ground plane
AMONG µModule PRODUCTS. REVIEW EACH PACKAGE
below the LTM8027 and the circuit components.
LAYOUT CAREFULLY. RT (Pin B1):
The RT pin is used to program the switching
VIN (Bank 3):
The VIN pins supply current to the LTM8027’s frequency of the LTM8027 by connecting a resistor from internal regulator and to the internal power switch. These this pin to ground. The Applications Information section of pins must be locally bypassed with an external, low ESR the data sheet includes a table to determine the resistance capacitor (see Table 2). value based on the desired switching frequency. Minimize
V
capacitance at this pin.
OUT (Bank 1):
Power Output Pins. Apply the output filter capacitor and the output load between these and
SYNC (Pin C1):
The SYNC pin provides an external clock the GND pins. input for synchronization of the internal oscillator. The
AUX (Pin A7):
Low Current Voltage Source for BIAS1 RT resistor should be set such that the internal oscillator and BIAS2. In many designs, the BIAS pin is connected frequency is 10% to 25% below the external clock fre- to V quency. This external clock frequency must be between OUT by way of the AUX pin. The AUX pin is internally connected to V 100kHz and 500kHz. If unused, tie the SYNC pin to GND. OUT and is placed near the BIAS pins to ease printed circuit board routing. Although this pin is internally For more information see Oscillator Sync in the Application connected to V Information section of this data sheet. OUT, do NOT connect this pin to the load. If this pin is not tied to BIAS1 and BIAS2, leave it floating.
ADJ (Pin A2):
The LTM8027 regulates its ADJ pin to 1.23V.
BIAS1 (Pin A6):
The BIAS1 pin connects to the internal Connect the adjust resistor from this pin to ground. The power bus. Connect to a power source greater than 8.5V. value of RADJ is given by the equation: If the output is greater than 8.5V, connect it to this pin. If RADJ = 613.77/(VOUT – 1.23) the output voltage is less, connect this to a voltage source between 8.5V and 15V. where RADJ is in kΩ.
BIAS2 (Pin A3):
Internal Biasing Power. Connect to AUX
SS (Pin A5):
The soft-start pin is used to program the (if 24V or less) or a voltage source above 3V. Do not leave supply soft-start function. Use the following formula to BIAS2 floating. calculate CSS for a given output voltage slew rate:
RUN (Pin A4):
Tie the RUN pin to ground to shut down CSS = 2µA(tSS/1.231V) the LTM8027. Tie to 1.4V or more for normal operation. The pin should be left unconnected when not using the The RUN pin is internally clamped to 5V, so when it is soft-start function. pulled up, be sure to use a pull-up resistor that limits the current into the RUN pin to less than 1mA. If the shutdown feature is not used, tie this pin to the VIN pin through a pull-up resistor. 8027fd For more information www.linear.com/LTM8027 9 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Order Information Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Typical Applications Package Photograph Package Description Revision History Typical Application Related Parts