adm1203 Analog Devices, Inc., adm1203 Datasheet - Page 6

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

ADM1203
TIMER FUNCTION
The TIMER pin handles several key functions with an external
capacitor, C
COMP1 (0.2V) and COMP2 (1.3V). The four timing current
sources are:
The 100µA is a non-ideal current source approximating a 7k
resistor below 0.4V.
INITIAL TIMING CYCLE
When the card is being inserted into the bus connector, the
long pins mate first which brings up the supply VIN at time
point 1 of Figure 7. The ADM1203 is in reset mode as the ON
pin is low. GATE is pulled low and the TIMER pin is pulled low
with a 100µA source. At time point 2, the short pin makes
contact and ON is pulled high. At this instant, a start-up check
requires that the supply voltage be above UVLO, the ON pin
beabove1.3Vand the TIMER pin voltage be less than 0.2V.
When these three conditions are fulfilled, the initial cycle
begins and the TIMER pin is pulled high with 5µA. At time
point 3, the TIMER reaches the COMP2 threshold and the first
portion of the initial cycle ends. The 100µA current source then
pulls down the TIMER pin until it reaches 0.2V at time point 4.
The initial cycle delay (time point 2 to time point 4) is related to
C
t
When the initial cycle terminates, a start-up cycle is activated
and the GATE pin ramps high. The TIMER pin continues to be
pulled down towards ground.
INITIAL
TIMER
•
•
•
•
~= 272.9 x C
by equation:
5µA pull-up
60µA pull-up
2µA pull-down
100µA pull-down
TIMER
. There are two comparator thresholds:
TIMER
ms/uF
(4)
Rev. PrD | Page 6 of 8
V TIMER
I RSENSE
V GATE
V TIMER
V OUT
V GATE
V OUT
V ON
V IN
V ON
V IN
RE SET
MODE
RESET
MODE
Figure 8: Current Limiting at Start-up
Preliminary Technical Data
Figure 7: Normal Start-up
5µA
INITIA L
CY CLE
INITIAL
CYCLE
100µA
S TART -UP
START-UP
CYCLE
CYCLE
60µA
NORM AL
NORMAL
CYCLE
CYCLE
V TH
2µA
100µA