AN603 Controller Datasheet

AN603 Datasheet PDF, Equivalent


Part Number

AN603

Description

Designing With the Si9978DW Configurable H-Bridge Controller

Manufacture

Vishay Siliconix

Total Page 6 Pages
Datasheet
Download AN603 Datasheet


AN603
AN603
Vishay Siliconix
Designing With the Si9978DW Configurable H-Bridge Controller
Wharton McDaniel
Currently, there are a number of fully integrated H-bridges on
the market. Both bipolar and MOS technologies have been
used to create these parts. However, all of them suffer from
problems such as limited current handling capability, large
package size, and difficulty of assembly. The Si9978DW
addresses these problems with an architecture that allows
flexible current handling capability, small size, and ease of
assembly. Instead of trying to integrate the power devices with
the controller on a single piece of silicon, the Si9978DW
approach is to separate the controller from the MOSFETs. The
benefit is efficient manufacture of both the controller and the
MOSFETs, the flexibility to select the optimum MOSFET for the
application, and the ability to use surface-mount parts for both
the controller and MOSFETs which makes assembly easier.
Altogether this means a low cost H-bridge solution.
The Si9978DW is a monolithic controller designed to be used
with LITTLE FOOTR power MOSFETs to create an
all-n-channel H-bridge or two separate half bridges. In addition
to this functional flexibility, the dual function allows
standardization of components and reduces inventory costs.
The Si9978DW features integral high-side drive circuitry and
an internal voltage regulator, which allows operation over a 20-
to 40-V dc input voltage range. Protection features include
cross-conduction protection, current limiting, and undervoltage
lockout. The FAULT outputs indicate when undervoltage or
overcurrent shutdown has occurred. The Si9978DW is
packaged in a 24-pin wide body SOIC.
CONTROL LOGIC
The Si9978 has two modes of operation, full H-bridge, and
independent half-bridge. The mode of operation determines
the function of the input pins and the FAULT outputs. With the
MODE pin at logic 1, which is the default condition, the Si9978
functions as a full H-bridge. With the MODE pin at logic 0, the
Si9978DW functions as two independent half-bridges. The
definitions of the control inputs depend on the mode of
operation. All control inputs are pulled up to VDD. The FAULT
outputs are open drain. Truth Tables have been provided for
each mode of operation.
V+ 24
www.DataSheet4U.com
VDD
1
DIR/INA
QS/INB
PWM/ENB
MODE
BRK
EN/ENA
CL/FAULTB
FAULT/FAULTA
RA/CA
3
5
4
6
7
2
8
9
11
RB/CB
12
Low-Voltage
Regulator
VDD
Low-Side
U.V. Lockout
VDD
VDD
VDD
VDD
VDD
VDD
CAPA
CAPB
High-Side
U.V. Lockout
Input
Logic
One Shot
One Shot
Bootstrap Reg.
Charge Pump
Bootstrap Reg.
Charge Pump
VDD
VDD
23 CAPA
21 GTA
22
SA
19 CAPB
17 GTB
18
SB
20 GBA
16 GBB
15
GND
+ 13 ILA+
+ 14 ILB+
FIGURE 1. The Si9978 is made up of the control logic, the gate drive outputs, VDD regulator, and protection circuitry.
Document Number: 70574
08-Jun-00
www.vishay.com S FaxBack 408-970-5600
1

AN603
AN603
Vishay Siliconix
Full H-Bridge Operation
When operating as a full H-bridge, the control inputs become
DIR, QS, PWM, BRK, and EN. When connecting the bridge for
anti-phase operation, the DIR input is driven by the control
system PWM signal. When connected for sign-magnitude
operation, the DIR input controls direction, and the system
PWM signal drives the PWM input.
Independent Half-Bridge Operation
In the independent half-bridge mode, the control inputs
become the independent controls for each half-bridge, INA,
ENA, INB, ENB. The BRK input is not functional in this mode
of operation.
Gate Drive Outputs
Each half-bridge output is driven by a pair of n-channel
MOSFETs. These are controlled by a low- and a high-side gate
driver. They have been designed to drive a 600-pF load with
a 110-ns rise time and a 50-ns fall time.
The low-side gate is driven directly from the commutation logic
and is powered by VDD. This means that VDD must be
decoupled with a 1-mF capacitor; otherwise the turn-on surge
current can cause VDD to drop to the level of an undervoltage
condition. The high side is a floating circuit powered from a
combination bootstrap/charge pump supply. The bootstrap
capacitor is charged to VDD when ever the low-side MOSFET
is turned on. At all other times, the charge pump keeps the
bootstrap capacitor charged, replacing the charge used in
powering the high-side circuitry and in turning on the MOSFET.
The value of the bootstrap capacitor is a function of the
MOSFET being driven. The bootstrap voltage should not drop
more than 1 V as the result of a MOSFET turn-on. For a 60-V
dual n-channel MOSFET like the Si4946EY, 30 nC (Qg) is
required for turn-on at a Vgs of 10 V. Using the equation C =
Qg/VGS, 30 nF is required to provide sufficient charge for
turn-on. To meet the criterion of dropping only 1 V at turn-on,
the capacitor needs to be 10 times as large, making the
equation CBOOT = 10(Qg/VGS). This makes the minimum value
of CBOOT equal to 0.039 mF. Table 3 gives minimum
recommended values for several MOSFETs that might be
used with the Si9979. This minimum recommended value is
one standard value above the minimum calculated value.
MODE
1
DIR/
INA
1
11
www.DataSh1eet4U.co0m
10
1X
1X
1X
1X
EN/
ENA
1
1
1
1
1
0
1
X
TABLE 1. HĆBRIDGE MODE
QS/ PWM/
INB ENB BRK ILA+
1 0L
ILB+
X
GTA
H
GBA
L
GTB
L
GBB
CL/
FAULTB
1
FAULT/
FAULTA
1
0
0L X
LL
11
1
0L XL
HL
1
1
0 0L XL
L1
1
XX
XX
1L
XL
X LHLH
X LLLL
1
1
1
1
XX
0
X LLLL
XX
XX
X LLLL
1
0
Condition
Normal
Operation
Brake
Disable
Over-current
Undervoltage
on VDD
MODE
0
0
0
0
0
0
0
DIR/
INA
1
0
X
X
X
X
X
EN/
ENA
1
1
0
0
1
X
X
QS/
INB
X
X
1
0
X
X
X
TABLE 2. HALFĆBRIDGE MODE
PWM/
ENB
0
0
1
1
BRK
X
X
X
X
ILA+
L
L
L
L
ILB+
L
L
L
L
GTA
H
L
L
L
GBA
L
H
L
L
GTB
L
L
H
L
GBB
L
L
L
H
CL/
FAULTB
1
1
1
1
FAULT/
FAULTA
1
1
1
1
XX
X L L XX
1
1 XX
XX L L
1
XXX
X LLLL
0
0
Condition
Normal
Operation
Over-current
on A
Over-current
on B
Undervoltage
on VDD
www.vishay.com S FaxBack 408-970-5600
2
Document Number: 70574
08-Jun-00


Features AN603 Vishay Siliconix Designing With t he Si9978DW Configurable H-Bridge Contr oller Wharton McDaniel Currently, there are a number of fully integrated H-bri dges on the market. Both bipolar and MO S technologies have been used to create these parts. However, all of them suff er from problems such as limited curren t handling capability, large package si ze, and difficulty of assembly. The Si9 978DW addresses these problems with an architecture that allows flexible curre nt handling capability, small size, and ease of assembly. Instead of trying to integrate the power devices with the c ontroller on a single piece of silicon, the Si9978DW approach is to separate t he controller from the MOSFETs. The ben efit is efficient manufacture of both t he controller and the MOSFETs, the flex ibility to select the optimum MOSFET fo r the application, and the ability to u se surface-mount parts for both the con troller and MOSFETs which makes assembl y easier. Altogether this means a low cost H-bridge solution. T.
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