MIC2594-1YM Micrel Inc, MIC2594-1YM Datasheet - Page 14

• Manufacturer Part Number: MIC2594-1YM
• Description: Negative Voltage Hot-Swap Controller -
• Manufacturer: Micrel Inc
• Type: Hot-Swap Controllerr

Specifications of MIC2594-1YM

• Applications: General Purpose
• Internal Switch(s): No
• Voltage - Supply: -19 V ~ -80 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (0.154", 3.90mm Width)
• Family Name: MIC2594
• Package Type: SOIC
• Operating Supply Voltage (min): -19V
• Operating Supply Voltage (max): -80V
• Operating Temperature (min): -40C
• Operating Temperature (max): 85C
• Operating Temperature Classification: Industrial
• Product Depth (mm): 3.94mm
• Product Height (mm): 1.48mm
• Product Length (mm): 4.93mm
• Mounting: Surface Mount
• Pin Count: 8
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Applications Information
Optional External Circuits for Added Protection/Perfor-
mance
In many telecom applications, it is very common for circuit
boards to encounter large-scale supply-voltage transients
in backplane environments. Because backplanes present a
complex impedance environment, these transients can be
as high as 2.5 times steady-state levels, or 120V in worst-
case situations. In addition, a sudden load dump anywhere
on the circuit card can generate a very high voltage spike
at the drain of the output MOSFET which, in turn, will ap-
pear at the DRAIN pin of the MIC2588/MIC2594. In both
cases, it is good engineering practice to include protective
measures to avoid damaging sensitive ICs or the hot swap
controller from these large-scale transients. Two typical
scenarios in which large-scale transients occur are de-
scribed below:
September 2005
MIC2588/MIC2594
1. An output current load dump with no bypass (charge
bucket or bulk) capacitance to V
if L
resulting peak short-circuit current prior to the
MOSFET turning off would reach:
If there is no other path for this current to take
when the MOSFET turns off, it will avalanche the
drain-source junction of the MOSFET. Since the
total energy represented is small relative to the
sturdiness of modern power MOSFETs, it’s unlikely
that this will damage the transistor. However, the
actual avalanche voltage is unknown; all that can
be guaranteed is that it will be greater than the
V
BD(D-S)
LOAD

56V 0.7 s
5 H

= 5µH, V
of the MOSFET. The drain of the transistor

-48V RTN
System
Reset
-48V

100V
*D1

IN

IN
*R7
10kΩ
7.8A
0.47µF
Figure 6 Optional Components for Added Performance/Protection
= 56V and t
C1
12.4kΩ
R3
1%
* Optional components (See Applications Information for more details)
An SOT-363 is recommended for M2.
D2 is a 68V, 1W Zener diode.
D2 is
EE
*M2
698kΩ
OFF
1%
R1
. For example,
11.8kΩ
1%
R2
C2
0.22uF
= 0.7µs, the
47kΩ
*R5
1
2
3
4
/PWRGD
VEE
OV
UV
MIC2588-2BM
0.47uF
R
0.01Ω
*C6
SENSE
5%
14
SENSE
For many applications, the use of additional circuit compo-
nents can be implemented for optimum system performance
and/or protection. The circuit, shown in Figure 6, includes
several components to address some the following system
(dynamic) responses and/or functions: 1) suppression of
transient voltage spikes, 2) elimination of false “tripping” of the
circuit breaker due to undervoltage and overcurrent glitches,
and 3) the implementation of an external reset circuit.
It is not mandatory that these techniques be utilized, how-
ever, the application environment will dictate suitability. For
protection against sudden on-card load dumps at the DRAIN
pin of the MIC2588/MIC2594 controller, a 68V, 1W, 5% Zener
diode clamp (D2) connected from the DRAIN to the VEE of
the controller can be implemented, as shown. To protect
the controller from large-scale transients at the card input,
a 100V clamp diode (D1, SMAT70A or equivalent) can be
used. In either case, very short lead lengths and compact
layout design is strongly recommended to prevent unwanted
transients in the protection circuitry. Power buss inductance
often produces localized (plug-in card) high-voltage transients
during a turn-off event. Managing these repeated voltage
stresses with sufficient input bulk capacitance and/or tran-
sient suppressing diode clamps is highly recommended for
maximizing the life of the hot swap controller(s).
DRAIN
GATE
VDD
2.7kΩ
*R6
2. If the load’s bypass capacitance (for example,
8
7
6
5
is connected to the DRAIN pin of the MIC2588/
MIC2594, and the resulting transient does have
enough voltage and energy to damage this, or any,
high-voltage hot swap controller.
the input filter capacitors for DC-DC converter
module(s)) are on a board from which the board
with the MIC2588/MIC2594 and the MOSFET can
be unplugged, the same type of inductive transient
damage can occur to the MIC2588/MIC2594.
0.33uF
C3
*D2
68V
10Ω
SUM110N10-09
R4
M1
10kΩ
R
FDBK
C
10nF
100V
47uF
FDBK
C5
-48V RTN
0.1uF
C4
-48V
OUT
M9999-083005
Micrel