Micrel, Inc.

MIC45205

Pin Description

MIC45205

Pin Number

Pin Name

Pin Function

1

GND

Analog Ground. Connect bottom feedback resistor to GND. GND and PGND should be

connected together at a low impedance point.

2, 3

5VDD

Internal +5V Linear Regulator Output. Powered by VIN, 5VDD is the internal supply bus for the

device. In the applications with VIN<+5.5V, 5VDD should be tied to VIN to by-pass the linear

regulator.

4, 5

PVDD

PVDD. Supply input for the internal low-side power MOSFET driver.

6, 7, 8, 45, 52

PGND

Power Ground. PGND is the return path for the step-down power module power stage. The

PGND pin connects to the sources of internal low-side power MOSFET, the negative terminals of

input capacitors, and the negative terminals of output capacitors.

9 - 12,

30 - 35

SW

The SW pin connects directly to the switch node. Due to the high-speed switching on this pin, the

SW pin should be routed away from sensitive nodes. The SW pin also senses the current by

monitoring the voltage across the low-side MOSFET during OFF time.

13 -19

PVIN

Power Input Voltage. Connection to the drain of the internal high side power MOSFET. Connect

an input capacitor from PVIN to PGND.

20 - 29

VOUT

Output Voltage. Connected to the internal inductor, the output capacitor should be connected

from this pin to PGND as close to the module as possible.

36 - 38

RIA

Ripple Injection Pin A. Leave floating, no connection.

39

RIB

Ripple Injection Pin B. Connect this pin to FB.

40, 41

ANODE

Anode Bootstrap Diode. Anode connection of internal bootstrap diode, this pin should be

connected to the PVDD pin.

42 - 44

BST

Connection to the internal bootstrap circuitry and high-side power MOSFET drive circuitry. Leave

floating, no connection.

46

FB

Feedback. Input to the transconductance amplifier of the control loop. The FB pin is referenced to

0.8V. A resistor divider connecting the feedback to the output is used to set the desired output

voltage. Connect the bottom resistor from FB to GND.

47

PG

Power Good. Open Drain Output. If used, connect to an external pull-up resistor of at least

10kohm between PG and the external bias voltage.

48

EN

Enable. A logic signal to enable or disable the step-down regulator module operation. The EN pin

is TTL/CMOS compatible. Logic high = enable, logic low = disable or shutdown. EN pin has an

internal 1M

Ω (typical) pull-down resistor to GND. Do not leave floating

49

VIN

Internal 5V Linear Regulator Input.

A 1μF ceramic capacitor from VIN to GND is required for

decoupling.

50

FREQ

Switching Frequency Adjust. Use a resistor divider from VIN to GND to program the switching

frequency. Connecting FREQ to VIN sets frequency = 600kHz.

51

ILIM

Current Limit. Connect a resistor between ILIM and SW to program the current limit.

April 15, 2014

3

Revision 1.0