1. Overview and Setup
1.1 Hardware
Si8284-EVB can be used to demonstrate the isolated gate drive capabilities of the installed Si8284CD-IS. The Si8284 includes a DC-
DC converter used to supply isolated power to the gate driver.
Si8284 Low Voltage Side Connections
Supply power to the input side of Si8284 by applying 12 to 24 VDC to VDDP at terminal block J1. LED D6 above terminal block J1
illuminates to show power applied. For interfacing to the low voltage side of Si8284, VDDA supply must be between 3.0 and 5.5 V
DC
.
Either a separate supply can be connected to VDDA terminal on J1 or 5 V
DC
can be derived from VDDP through the regulator circuit
and directed to VDDA through a jumper at JP4. LED D5 below terminal block J1 illuminates to show VDDA power applied.
J6-J11 single pin headers provide access to the IN+, IN-, RSTb, and SH inputs and FLTb and RDY outputs of the Si8284. These sig-
nals can be brought out to an external microcontroller using a ribbon cable (not supplied). FLTb is an open drain output and has a pull-
up resistor to VDDA. The open drain output allows multiple gate drivers FLTb outputs to share the same microcontroller input.
Driver functionality can be exercised without microcontroller by applying a GNDA referenced PWM signal from a function generator to
the IN+ and IN- inputs. Maximum input voltage is VDDA.
DC-DC Operation
The isolated DC-DC converter is set to generate (with respect to VMID) 15 V for VDDB and -9 V for VSSB. LED D8 and D7 illuminates
when VDDB and VSSB are powered respectively. DC-DC operation can be turned off by pulling terminal J11 to VDDA.
Si8284 Isolated Gate Drive Connections
There is a provision for a MOSFET or an IGBT in a TO-247 package (not supplied) at Q1.
From top to bottom, the through holes for the transistor leads are Source, Drain, and Gate. Load transistors are biased by applying
voltage across VPWR and VMID terminals of J2. This voltage should not exceed the rated V
DS
of the transistor or 300 V, whichever is
lower. Supply voltage constraints are summarized in the table below.
Note:
Si8284 can drive the gate of either high-side or low-side MOSFET or IGBT in a bridge configuration. VMID is the same net as the
load when driving the gate of a high side MOSFET or IGBT. For a gate drive for a low side MOSFET or IGBT, VMID is the return for the
load.
Table 1.1. Supply Voltage Constraints
3.0 V ≤ VDDA – GNDA ≤ 5.5 V
12 V ≤ VDDP ≤ 24 V
VSSB ≤ VMID < VDDB
UVLO +
1
< VDDB - VSSB < 30 V
VPWR < VDS (Q)
VPWR < 300 V
|GNDA – VSSB| < 5 kV
Note:
1. UVLO+ for the Si8284CD-IS is 12.3 V.
UG168: Si8284-EVB User's Guide
Overview and Setup
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