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UC3178
Full Bridge Power Amplifier
• Precision Current Control
•±450mA Load Current
• 1.2V Typical Total Vsat at
450mA
• Programmable Over-Current
Control
• Range Control for 4:1 Gain
Change
• Compensation Adjust Pin for
Range Bandwidth Control
• Inhibit Input and UVLO
• 3V to 15V Operation
• 12mA Quiescent Supply
Current
The UC3178 ful l-bridge power amplifier, rated for continuous output current
of 0.45 Amperes, i s intended for use in demanding servo applications. This
device includes a preci sion current sense amplifier that senses load current
with a single resistor in series with the load. The UC3178 is optimized to con sume a minimum of supply current, and is designed to operate in both 5V
and 12V systems. The power output stages have a l ow saturation voltage
and are protected with current limiting and thermal shutdown. When inhibited,
the device will draw less than 1.5mA of total supply current.
Auxiliary functions on this device include a load current sensing and rectification function that can be configured with the device’s over-current comparator
to provide tight control on the maximum commanded load current. The closed
loop transconductance of the configured power amplifier can be switched between a high and l ow ran ge wi th a si ngl e lo gic input. The 4:1 change in gain
can be used to extend the dynamic range of the servo loop. Bandwidth variations that would otherwise result with the gain change can be controlled w ith
a compensation adjust pin.
This device is packaged a power PLCC, "QP" package which maintains a
standard 28-pin outline, but with 7 pins along one edge directly tied to the die
substrate for improved thermal performance.
FEATURES
BLOCK DIAGRAM
DESCRIPTION
UDG-92010
PLCC - 28 (Top View)
QP Package
ABSOLUTE MAXIMUM RATINGS
THERMAL DATA
UC3178
Input Supply Vo ltag e, (VIN(+), VC(+) ). . . . . . . . . . . . . . . . . . 20V
O/C Sense, Logic Input s, and REF Input
Maximum forced vo lta g e. . . . . . . . . . . . . . . . . -0.3V to 10V
Maximum forced cu rr ent . . . . . . . . . . . . . . . . . . . . . . ±10mA
A & B Amplifier Inputs . . . . . . . . . . . . . -0.3V to (V
IN(+) + 1.0V)
O/C Indicate O pen Collector Output Volta ge. . . . . . . . . . . . 20V
A and B Output Cur ren ts(co nt in uous )
Source . . . . . . . . . . . . . . . . . . . . . . . . . . . . Internally Limited
Sink . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.6A
Output Diode Current (pulsed)* . . . . . . . . . . . . . . . . . . . . . 0.5A
O/C Ind Output Cu rrent (c ont inuous) . . . . . . . . . . . . . . . . 20mA
Operating Jun ctio n Tem per atur e. . . . . . . . . . . . . . . . . . +150 °C
Storage Temperature. . . . . . . . . . . . . . . . . . . -65°C to +150 ° C
*Notes: Unless other wise indicat ed , voltag es are refer enc ed to
ground and curre nts are posit ive into , negat ive out of, the specified terminals, "Pu lsed" is defin ed as a less than 10% dut y cycle pulse with a maximum dura tion of 500
µs.
QP package: (see pac kaging sect ion of UICC data book for more
details on therm al perfor m ance )
Thermal Resistance Junction to Leads, θjl . . . . . . . . 15°C/W
Thermal Resistance Junction to Ambient, θja . . . 30-40°C/W
CONNECTION DIAG RAM
PARAMETER TEST CONDITIONS MIN TYP MAX UNITS
Input S u p pl y
V
IN (+)Supply Cur rent 12 16 mA
VC(+) Supply Current IOUT = OA 1.2 2.0 mA
Total Supply Current Supplies = 5V,I
OUT = OA 12 16 mA
Supplies = 12V,I
OUT = OA 13 18 mA
V
IN(+) UVLO Threshold low to high 2.6 2.8 V
UVLO Threshold Hysterisis 300 mV
Over-Cur ren t (O/C) Comp ara tor
Input Bias Current V input = 0.8V -1.0 -.01 µA
Thresholds low to high 0.97 1.0 1.03 V
Threshold Hys terisis 85 100 115 mV
O/C IND Vsat I
OUT = 5mA, V input low 0.2 0.45 V
O/C IND Leakage V
OUT = 20V 5.0 µA
Power Amplifiers A and B
Input Off set Voltage A Amplifier, V
CM = 6V 4.0 mV
B Amplifier, V
CM = 6V 12.0 mV
Input Bias Current V
CM = 6V -500 -50 µΑ
CMRR V
CM = 0.5 to 13V, Supplies = 15V 70 90 dB
PSRR VIN(+) = 4 to 15V, VCM = 1.5V 70 90 dB
Large Signal Volta ge G ain Supplies = 12V, V
OUT = 1V, IOUT = 3 00mA
to V
OUT = 10.5V, IOUT = -300mA 3.0 15.0 V/mV
Unless otherwise stat ed spe cifica tion s hold for TA = 0°C to 70°C, VC(+) = VIN(+) =
12V, REF Input = VIN(+)/2, O/C Inpu t & Inhibit Input = 0V.
Note: The above nu mbers for θjl are maximums for the limiti ng
thermal resist anc e of the packa ge in a standa rd moun ting configuration . The
θ
ja numbers are meant t o be guideline s for the
thermal perfor ma nce of the device/pc- boar d sy stem . All of the
above numbers assume no ambient airflow.
PACKAGE PIN FUNCTION
FUNCTION PIN
Inhibit 1
O/C Force 2
O/C Sen se 3
Range 4
C/S(+) 5
Comp Adj 6
O/C Ind 7
A
IN(+) 8
A
IN(-) 9
V
C(+) Supply 10
A Output 11
Pwr Gnd 12
Pwr Gnd 13
Pwr Gnd 14
Pwr Gnd 15
Pwr Gnd 16
Pwr Gnd 17
Pwr Gnd 18
B Output 19
V
IN(+) 20
B
IN(-) 21
B
IN(+) 22
REF Input 23
C/S(+) 24
C/S Out 25
IDIF Out 26
IDIF REF 27
Ground 28
ELECTRICAL CHARACTERIST ICS :
2
PARAMETER TEST CONDITIONS MIN TYP MAX UNITS
Power Amplifiers A & B (cont.)
Gain Bandwit h Prod uct A Amplifier 2.0 MHz
B Amplifier 1.0 MHz
Slew Rate 1.0 V/µs
High-Side Current Limit 0.45 0.65 A
Output Saturation Voltage High-Side, I
OUT = -100mA 0.75 V
High-Side, I
OUT = -300mA 0.85 V
High-Side, IOUT = -450mA 0.9 V
Low-Side, I
OUT = 100mA 0.2 V
Low-Side, I
OUT = 300mA 0.25 V
Low-Side, I
OUT = 450mA 0.30 V
Total Vsat, I
OUT = 100mA 0.95 1.2 V
Total Vsat, I
OUT = 300mA 1.05 1.4 V
Total Vsat, I
OUT = 450mA 1.25 1.6 V
High-Side Diode, Vf I
D = 450mA 1.30 V
Current Sense Amplifier
Input Offset Voltage V
CM = 6V, Low range mode 2.0 mV
High range mode 4.0 mV
Input Offset Change V
CM = -1V to 13V, Supplies = 12V, Low Range Mode 2000 µV/V
with Common Mode I npu t V
CM = -1V to 13V, Supplies = 12V, High Range Mode 4000 µV/V
Voltage Gain V
DIFF = +1.0 to -1.0V, Vcm = 6V, High Range Mode 0 .485 0.50 0.515 V/V
V
DIFF = +1.0 to -1.0V, Vcm = 6V, Low Range M ode 1.95 2.0 2.05 V/ V
Saturation Voltage Low-Side, I
OUT = 1mA 0.1 0.3 V
High-Side, IOUT = -1mA, Referenced to = VIN(+) 0.1 0.3 V
Input Bias Cu rrent at Ref. Input (REF Input - C/S( +))/48kohm s, Tj = 25°C 152127µA/V
Load Curre nt Sen se and Recti fic atio n
Sense Buffer Off set Voltage REF I nput to IDIF REF, I
OUT =
±
1mA 10 mV
Sense Buff er CMR R I
OUT =
±1mA, REF Input = 2V to 10V
70 90 dB
IDIF REF to IDIF Out Cur ren t IDIF =
± 100
µA, IDIF Out = 1V 0.95 1.0 1.05 A/A
Ratio IDIF =
±1mA, IDIF Out = 1V
0.94 1.0 1.06 A/A
IDIF Out Supply Sen sitivit y IDIF Out =
± 1mA, V
IN
(+)
= 4V to 15V,REF Input = 2V
1.0 5.0 µA/ V
IDIF Out Commo n Mode Sensitivit y IOUT =
±1mA, REF Input = 2V to10V, IDIF Out = 1V
(delta IDIF Out/de lta REF Inpu t) 1.0 5.0 µA/V
Auxi li ar y F u n ctions
Inhibit Input Threshold 0.6 1.1 1.7 V
Inhibit Input Current Inhibit Input = 1.7V -1.0 -0.5 µA
O/C Force Input Threshold 0.6 1.1 1.7 V
O/C Force Input Current O/C Force Input = 1.7V 50 100 µA
Range Input Threshold 0.6 1.1 1.7 V
Range Input Curre nt Range Input = 1.7V 50 100 µA
COMP ADJ Pin Satura tion Range Input = 0V, Pin Current =
±500µA, Referenced
Voltage to A
OUT 0.02 0.1 V
COMP ADJ Leakage Current Range Input = 1.7V, Supplies = 12V
AOUT
-VComp Adj = ±6V 5.0 µA
Total Supply Curren t When Inhib ited V
IN(+) and VC(+) currents 1.0 1.5 mA
Thermal Shutdown Temperature 165 °C
UC3178
Unless otherwise stat ed spe cifica tion s hold for TA = 0°C to 70°C , VC(+) = VIN(+) = 12V,
REF Input = V
IN(+)/2, O/C In p ut & Inhibit Input = 0V.
ELECTRICAL
CHARACTERISTICS (cont.):
3
A & B OUT: Outputs for the A & B power amplifiers,
providing differential drive to the load during normal operation. During a UVLO, Inhibit, or O/C condition both of
these outputs will be in a high, source only state. Highside diodes are i ncluded to ca tch inductive load currents
flowing into these pins, inductive kicks on the low-side are
caught by the high-side output transistors.
A
IN(+): Non-inverting input to the A amp lifier. Normally tied
to the REF In pu t wh en the cu rr ent sen se am plif ier is used.
A
IN(-): Inverting input to the A amplifier. Used as the sum-
ming node to close the loop on the overall power
amplifier.
B
IN(+): Non-inverting input to the B amplifier. This pin nor-
mally sets the reference point for the differential voltage
swing at the load.
B
IN(-): Inverting input to the B amplifier. Used to program
the gain of the B amplifier.
COMP ADJ: The compensation adjust pin allows the user
to provide an auxiliary compensation network f or t h e A amplifier that is only active when the current sense amplifier is
in the low range. With this option, the user can control the
change in bandwidth that would otherwise result from the
gain change in the feedback loop.
C/S(+): The non-inv erting input to the current sense amplifier is typically tied to the load side of the series current
sense resistor. This pin can be pulled below ground during
an abrupt load current change with an inductive load.
Proper operation of the current sense amplifier will result if
this pin does not go below ground by an amount greater
than:
(REF In put / 2 ) - 0. 3V.
C/S(-): The inverting input to the current sense amplifier is
typically tied to the connection between the B amplifier
output and the current sense resistor that is in series with
the load.
C/S Output: The output of the current sense amplifier has
a 1.5mA current source pull-up and an active NPN pulldown. The output will pu ll t o w ithin 0.3V of either rail with
a load current of less than 1mA.
GND: Reference point for the internal reference, O/C
comparator, and other low-level circuitry.
IDIF OUT: Current source output pin. The value of the output current is nominally equal to the magnitude of the
current through the IDIF REF pin.
IDIF REF: Output of the IDIF sense buffer. Voltage on this
pin will track the applied voltage on the REF Input pin.
Current through this pin is full wave rectified and appears
as a current sourced from the IDIF OUT pin.
Inhibit : A high impe dance l ogic input th at di sabl es the A
and B power amplifiers, the IDIF sense buffer, and the
Current Sense amplifier. This input has an internal pull-up
that will inhibit the device if the input is left open.
O/C Force: Logic input that forces the O/C condition.
O/C IND: Open collector ouput that indicates, with an ac-
tive low state, an O/C condition.
O/C Sense: Input to the Over Current Comparator. When
this input is above its 1V threshold the low-side devices of
both the A & B power amplifiers will be disabled forcing a
high, source only , state at both outputs.
PWR GND: Current return for all high level circuitry, this
pin should be connected to the same potential as GND.
Range: When this pin is open or at a logic low potential,
the current sense ampli fier will be in its low range mode.
In this mode the voltage gain o f the amplifier will be 2. If
this pin is brough t to a logic high, the gain of the current
sense amplifier will change into its high range value of
0.5. This factor of four change in gain will vary the overall
transconductance of the power amplifier by the same ratio, with the transconductance being the highest in the
high mode. This feature al lows improved dynamic range
of load curren t control for a give n con trol input range and
resolution.
REF Input: Sets the Reference level at the C/S Output,
and is normally tied to the system reference level for inputs to the power amplifier.
V
IN(+): Provides bias supply to the device. The High-Side
drive to the power stages on both the A and B amplifiers
is referenced to this pin. The High-side saturation voltages, and UVLO are specified and measured with respect
to this supply pin.
V
C(+): Thi s supply pin is the high current supply to the
collectors o f the high-side NPN output devices on the A
and B ampl ifiers. This supply should be powered whenever the A or B amplifiers are to be activated. This pin can
operate approximately 400mV below the V
IN(+) supply
without affecting the voltage available to the load.
UC3178
PIN DESCRIPTIONS:
4
UC3178
UNITRODE INTEGRATED CIRCUITS
7 CONTINENTAL BLVD.• MERRIMACK, NH 03054
TEL (603) 424-2410 • FAX (603) 424-34 60
TYPICAL APPLICATION
Power amplifier transconductance
Go
=
Il
Vs
=
RB
RA
•
1
AV
CS
•
RS
Peak commanded load current
Il
MAX
=
V
o/c
•
RD
RS
•
AV
CS
•
RE
where:
Il
is the load current
Vs
is the input command voltage
AV
CS
is the current sense amplifier gain
= 2.0 in low range mode
= 0.5 in high range mode
V
O/C
is the 1.0V over-current comparator thresh old
UDG-92009
5
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