adm1203 Analog Devices, Inc., adm1203 Datasheet - Page 5

• Manufacturer Part Number: adm1203
• Description: Simple Tracker? With Circuit Breaker
• Manufacturer: Analog Devices, Inc.

Preliminary Technical Data
UP/DO WN
Figure 3. ADM1203-1 Power-Up and Power-Down Waveforms
UP/STOP
SLEW RATE CONTROL
Voltage tracking is achieved by controlling the slew rate of a
rising or falling supply by an external capacitor on the SLEW
pin. Alternatively, this pin can be overdriven with a supply
which will result in the output following this supply. The gate
responds to maintain ~100mV between the VOUTFB pin and
the SLEW pin
Figure 4. ADM1203-2 Power-Up and Power-Down Waveforms
V OLTAGE S
V OLTAGE S
OUTP UT
OUTP UT
Figure 6. Tracking up Waveforms
3.3V
2.5V
1.5V
3.3V
2.5V
1.5V
Rev. PrD | Page 5 of 8
CURRENT LIMIT CIRCUIT BREAKER FUNCTION
The ADM1203 features a current limiting circuit breaker.
When there is a sudden load current surge, such as a low
impedance fault, the bus supply voltage can drop significantly
to a point where the power to an adjacent card is
affected, causing system malfunctions. The ADM1203 fast
response current RS amplifier instantly limits current by
reducing the external FET GATE pin voltage. This
minimizes the bus supply voltage drop and permits power
budgeting and fault isolation without affecting neighboring
cards. A compensation circuit should be connected to
the GATE pin for current limit loop stability.
CALCULATING CURRENT LIMIT
The nominal fault current limit is determined by a RS
resistor connected between V
given by the equation below:
I
The minimum load current is given by Equation 2:
I
The maximum load current is given by Equation 3:
I
Note: The power rating of the RS resistor should be rated at the
fault current level. The RS resistor power rating must exceed
V
LIMIT(NOM)
LIMIT(MIN)
LIMIT(MAX)
CB(MAX
)
2
= V
/R
= V
= V
RS(MIN).
CB(MIN)
CB(MAX)
CB(NOM)
/ R
/ R
/ R
RS(MAX)
RS(MIN)
RS
CC
(3)
and the RS- pin as
(2)
(1)
ADM1203