PM8851D [STMICROELECTRONICS]
Short propagation delays;
| 型号： | PM8851D |
| 厂家： | 
ST |
| 描述： | Short propagation delays |
| 文件： | 总14页 (文件大小：422K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
PM8851
1 A low-side gate driver with configurable asymmetric sink/source
Datasheet - production data
Description
The PM8851 device is a high frequency single
channel low-side MOSFET driver specifically
designed to work with digital power conversion
microcontrollers, such as the STMicroelectronics
STLUX™ family of products.
SOT23-6L
The PM8851 has complementary output pins to
differentiate sink and source driving with a current
capability of respectively 1 A and 0.8 A.
Features
The input levels of the driver are derived by the
voltage present at the IN_TH pin (between 2 V
and 5.5 V). This pin is typically connected at the
same voltage of the microcontroller supply
voltage.
Low-side MOSFET driver
1 A sink and 0.8 A source capability
Complementary outputs for source and sink
driving
The PM8851 includes both input and output pull-
down resistors.
Ext. reference for input threshold
Wide supply voltage range (10 V ÷ 18 V)
Input and output pull-down resistors
Short propagation delays
UVLO circuitry for input and output stages is
present preventing the IC from driving external
MOSFET in unsafe condition.
Input and output UVLO
Table 1. Device summary
Wide operating temperature range:
-40 °C to 125 °C
Order code
Option
Package
SOT23-6L package
PM8851D
Low input threshold
SOT23-6L
Applications
SMPS
Digital lighting
Wireless battery chargers
Digitally controlled MOSFETs
October 2014
DocID027090 Rev 1
1/14
This is information on a product in full production.
www.st.com
Block diagram
PM8851
1
Block diagram
Figure 1. Block diagram
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PM8851
2/14
DocID027090 Rev 1
PM8851
Pin connection
2
Pin connection
Figure 2. Pin connection
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Table 2. Pinning
Description
Symbol
Pin
IC power supply. A voltage comprised between 10 V and 18 V can be connected
between this pin and GND to supply the IC.
VCC
GND
IN
1
2
3
Reference voltage connection.
Digital input signal for driver.
It is internally pulled down to GND with a 100 k (typ.) equivalent resistor.
Input for IN pin's threshold definition: a voltage can be applied obtaining the
values for VIH and VIL.
IN_TH
SNK
4
5
6
MOSFET gate drive sinking output controlled by the IN pin.
A pull-down equivalent resistor [100 k (typ.)] is present.
MOSFET gate drive sourcing output controlled by the IN pin.
SRC
A pull-down equivalent resistor [100 k (typ.)] is present.
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Maximum ratings
PM8851
3
Maximum ratings
Table 3. Thermal data
Parameter
Symbol
Value
Unit
Thermal resistance junction to ambient
RthJA
250
°C/W
(2-layer FR4 PCB, TA = 27 °C natural convection)
Thermal resistance junction to case
Maximum junction temperature
RthJC
TMAX
TSTG
TJ
130
°C/W
°C
150
Storage temperature range
-40 to 150
-40 to 150
-40 to 125
°C
Junction temperature range
°C
TA
Operating ambient temperature range
°C
Table 4. Absolute maximum ratings
Symbol
Parameter
Value
Unit
Note
IN unconnected, IN_TH = 3.3 V
Maximum IC supply voltage
Max. negative allowed voltage
Max. positive voltage at IN_TH pin
Max. negative allowed voltage
Maximum voltage at IN pin
19
- 0.3
5.5
V
V
VVCC,max
V
VIN_TH,max
- 0.3
5.5
V
V
VIN,max
Max. negative allowed voltage
Maximum RMS output current
Maximum RMS output current
- 0.3
40
V
ISRC,rms
ISNK,rms
mA
mA
60
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DocID027090 Rev 1
PM8851
Electrical characteristics
4
Electrical characteristics
(V = 12 V, V
= 3.3 V, T = - 40 ÷ 125 °C, unless otherwise specified).
CC
IN_TH
J
Table 5. Electrical characteristics
Symbol
Pin
Parameter
Test condition
Min. Typ. Max. Unit
IC SUPPLY
VCC
VCC Operating range
VCC Turn-on threshold
10
9
18
11
V
V
VCC,on
10
1
VUVLO,hyst VCC UVLO hysteresis
0.5
V
IST-UP
ICC,0
VCC Start-up current
VCC = VCC,on - 0.5 V
40
40
µA
µA
VCC Static supply current
VCC Operating supply current
IN = 0 V
ICC,op
See Figure 4 and Figure 5
IN_TH
VIN_TH
IN_TH Operating range
2
5.5
40
V
V
VIN_TH,UV IN_TH IN_TH UVLO
IIN_TH
IN_TH IN_TH pin bias current(1)
INPUT
IN_TH short with IN, rising edge
1.5
µA
(2)
(2)
VIH/VIN_TH
VIL/VIN_TH
VIN_Hyst
IIN
IN
IN
IN
IN
IN
IN
IN
Relative input high level threshold
Relative input low level threshold
Hysteresis
36
25
7
58
46
25
%
%
%
IN pin bias current
VIN = 5 V
50
µA
k
ns
ns
RINPD
Input pull-down resistance
IN to GD propagation delay
IN to GD propagation delay
VIN = VIN_TH
100
TD_LH
IN low to high, no load
IN high to low, no load
30
30
TD_HL
OUTPUT
Isrc = 100 mA, TJ = 25°C
Isrc = 100 mA, TJ =- 40 ÷ 125 °C(1)
Isnk =100 mA, TJ = 25°C
Isnk =100 mA, TJ =- 40 ÷ 125 °C(1)
VSRC = VCC / 2
11.4
11.4
0.53
0.53
940
1.1
V
V
SRC pin high level (when invoked
by IN pin)
VSRC,H
SRC
SNK
SRC pin low level (when invoked
by IN pin)
VSNK,L
ISRC
ISNK
tR
SRC Source current(1)
SNK Sink current(1)
SRC Rise time
mA
A
VSNK = VCC / 2
COUT = 470 pF
20
20
ns
ns
tF
SNK Fall time
COUT = 470 pF
SRC
RGPD
Pull-down resistor
SNK
100
k
1. Not tested in production.
2. Overlapping prevent by hysteresis VIN_Hyst
.
DocID027090 Rev 1
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14
Electrical characteristics
PM8851
Figure 3. Timings
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Figure 4. Operating supply current (no load)
Figure 5. Operating supply current
(C = 470 pF)
OUT
Figure 6. V power dissipation (PD) when no load is applied
CC
6/14
DocID027090 Rev 1
PM8851
Typical applications
5
Typical applications
Figure 7. Test circuit
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DocID027090 Rev 1
7/14
14
Typical applications
PM8851
Figure 9. Digitally controlled flyback converter
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Figure 10. Digitally controlled inverse buck converter (e.g.: LED controller)
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8/14
DocID027090 Rev 1
PM8851
Application guidelines
6
Application guidelines
6.1
Power supply
The PM8851 driver is intended to drive power MOSFETs used in power conversion
topologies at high speed. The accurate supply voltage definition guarantees an effective
driving in every condition. The voltage present at the IN_TH pin is used for the threshold
definition. It could be the same voltage used to supply the device providing the signal
applied to the IN pin, or it can be derived by the VCC pin, eventually using a voltage divider.
It is mainly suggested to provide IN_TH voltage starting from VCC voltage.
For example, an auxiliary, unregulated voltage can be used to be connected to both
PM8851 VCC pin and the input of a linear regulator that provides a well regulated supply
voltage for logic circuitry. The same low voltage is then provided to the IN_TH pin of the
PM8851.
If the IN_TH is derived directly by the VCC pin, the structure illustrated in Figure 12 can be
used.
Figure 11. Shared supply configuration
Figure 12. Independent supply configuration
It is mandatory to properly connect a 100 nF ceramic cap as close as possible to the VCC
pin to bypass the current's spikes absorbed by VCC during the gate charging.
Also IN_TH voltage should be filtered with a ceramic capacitor (10 nF to 100 nF), especially
when long traces are used to supply it; when derived by VCC a lighter filtering is allowed.
6.2
Layout suggestions
The small package of the PM8851 allows to place it very close to the gate of the driven
MOSFET: this reduces the risk of injecting high frequency noise produced by the driving
current running between the OUT pin and the MOSFET's gate pin.
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Application guidelines
PM8851
6.3
Driving switches
The IN pin truth table is reported in Table 6.
Table 6. PM8851 truth table (levels refer to unloaded condition of SNK and SRC)
PM8851
IN
SRC
SNK
High
Low
Vcc
Hi-Z
Hi-Z
GND
Differential MOSFET's driving strength is seldom necessary in topologies such as flybacks
or boost controlled in the peak current mode. A lower driving current is used to turn-on the
MOSFET in order to reduce the EMI produced by the Miller capacitance activation, while
a stronger turn-off action is suggested to minimize the turn-off delay and, consequently the
deviation between theoretical and practical behaviors.
The same asymmetrical driving strength is required when the IGBT switch is used: in fact
the driving strength control is mandatory to avoid latch-up phenomena intrinsically related
with this kind of the switch. The asymmetrical driving can be realized using different values
for the resistances placed between the MOSFET's gate and the SRC and SNK pins.
When low switching frequencies are required and propagation delays can be compensated,
it is possible to drive contemporary the IN pin and the IN_TH pin to exploit the relevant
UVLO threshold of the device (typ. 1.5 V) using the PM8851 as a fixed threshold device
without any external component: care has to be taken to consider additional propagation
delay (typ. 300 ns) after the falling edge of the input signal.
6.4
Power dissipation
Overall power dissipation can be evaluated considering two main contributions: the device
related consumption (PD) and the gate driving power demand (PG):
Equation 1
P
= P + P
D G
Tot
The device power consumption can be found in Figure 6 on page 6, it represents the power
required by the device to supply internal structures and pull-downs resistors.
The gate driving power dissipation is the power required to deliver to and from the
MOSFET's gate the required gate charge:
Equation 2
P = Q x V x f
sw
G
g
gs
The Q value can be found depicted into the MOSFET's datasheet for any applied V : V
g
gs
gs
can be considered equal to VCC.
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PM8851
Package information
7
Package information
In order to meet environmental requirements, ST offers these devices in different grades of
®
ECOPACK packages, depending on their level of environmental compliance. ECOPACK
specifications, grade definitions and product status are available at: www.st.com.
ECOPACK is an ST trademark.
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Package information
PM8851
Figure 13. SOT23-6L package outline
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Table 7. SOT23-6L package mechanical data
Dimensions(1)
Symbol
mm
inch
Typ.
Min.
Typ.
Max.
Min.
Max.
A
0.9
0
1.45
0.1
0.035
0
0.057
0.0039
0.0512
0.02
A1
A2
0.9
0.35
0.09
2.8
1.5
1.3
0.035
0.014
0.004
0.11
b
0.5
c
0.2
0.008
0.120
0.0689
D
3.05
1.75
E
0.059
e
0.95
0.037
H
2.6
0.1
0°
3
0.102
0.004
0°
0.118
0.024
10°
L
0.6
10°
(degrees)
1. Dimensions per JEDEC MO178AB.
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PM8851
Revision history
8
Revision history
Table 8. Document revision history
Date
Revision
Changes
23-Oct-2014
1
Initial release.
DocID027090 Rev 1
13/14
14
PM8851
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