FAN5038 Datasheet, PDF (2/15 Pages) Fairchild Semiconductor – Dual Voltage Controller for DSP Power

FAN5038
Pin Assignments
PRODUCT SPECIFICATION
LIN_EN
VREF
IFBH
IFBL
FBSW
VCCA
VFBL
GNDP
1 16
2 15
3 14
4 13
5 12
6 11
7 10
8
9
SWCTRL
CEXT
GNDA
VSCL
LDRV
VCCL
VCCP
SDRV
Pin Descriptions
Pin
Name
LIN_EN
VREF
IFBH
IFBL
FBSW
VCCA
VFBL
GNDP
SDRV
VCCP
VCCL
LDRV
VSCL
Pin
Number
1
2
3
4
5
6
7
8
9
10
11
12
13
Pin Function Description
Linear regulator enable input. Accepts TTL/open collector input levels. A logic level HIGH
on this pin disables the output of the linear regulator.
Voltage reference test point. This pin provides access to the internal precision 1.5V
bandgap reference and should be decoupled to ground using a 0.1µF ceramic capacitor.
No load should be connected to this pin.
High side current feedback for switching regulator. Pins 3 and 4 are used as the inputs
for the current feedback control loop and as the short circuit current sense points. Careful
layout of the traces from these pins to the current sense resistor is critical for optimal
performance of the short circuit protection scheme. See Applications Discussion for details.
Low side current feedback for switching regulator. See Applications Discussion for
details.
Voltage feedback for switching regulator. This input is active when a logic level LOW is
input on pin 16 (SWCTRL). Using two external resistors, it sets the output voltage level for
the switching regulator. See Applications Discussion for details.
Switching Regulator Vcc. Power supply for switching regulator control circuitry and
voltage reference. Connect to system 5V supply and decouple to ground with 0.1µF
ceramic capacitor.
Voltage feedback for linear regulator. Using two external resistors, this pin sets the
output voltage level for the linear regulator. See Applications Discussion for details.
Power Ground. Return pin for high currents flowing in pins 9, 10 and 12 (SDRV, VCCP and
LDRV). Connect to a low impedance ground. See Applications Discussion for details.
FET driver output for switching regulator. Connect this pin to the gate of the N-channel
MOSFET Q1 as shown in Figure 1. The trace from this pin to the MOSFET gate should be
kept as short as possible (less than 0.5"). See Applications Discussion for details.
Switching regulator gate drive Vcc. Power supply for SDRV output driver. Connect to
system 12V supply with R-C filter shown in Figure 1. See Applications Discussion for
details.
Linear Regulator Vcc. Power supply for LDRV output op-amp. Connect to system 12V
supply and decouple to ground with 0.1µF ceramic capacitor.
Output driver for linear regulator. Connect this pin to the base of an NPN transistor.
When pin 1 (LIN_EN) is pulled HIGH, the linear regulator is disabled and pin 12 will be
pulled low internally.
Low side current sense for linear regulator. Connect this pin between the sense resistor
and the collector of the power transistor. The high side current sense is internally connected
to pin 6 (VCCA). Layout is critical to optimal performance of the linear regulator short circuit
protection scheme. See Applications Discussion for details.
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