IR35203 Datasheet, PDF (26/56 Pages) International Rectifier – 6+1 Dual Output Digital Multi-Phase Controller

6+1 Dual Output Digital Multi-Phase Controller
IR35203
Figure 20 Input Current Sensing
PIN_ALERT
The IR35203 The IR35204 has a PIN_ALERT# pin to
alert the system when the input power has exceeded
a preset threshold. The pin is an open drain output
that is high until the input power threshold is exceeded
at which point it pulls low. The output stays low until
the input power drops below 90% of the Pin_Alert
threshold. The PIN_ALERT# pin will de-assert
100mS after the input power drops below 90% of the
PIN_ALERT threshold. In an Intel system the
Pin_alert pin is pulled up with a 4.99kohm resistor to
3.3 Vdc. The PIN is filtered by a 2KHz BW filter. The
PIN_ALERT# pin assertion will be belayed by up to
300uS.
OUTPUT CURRENT SENSING
The IR35203 provides per-phase output current
sensing to support accurate Adaptive Voltage
Positioning (AVP), current balancing, and over-current
protection. The differential current sense scheme
supports both lossless inductor DCR and R_{DS (}ON) (or
per-phase series precision resistor) current sensing
techniques.
For DCR sensing, a suitable resistor-capacitor
network of R_sen and C_sen is connected across the
inductor in each phase as shown in Figure 21 below.
The time constant of this RC network is set to equal
the inductor time constant (L/DCR) such that the
voltage across the capacitor C_sen is equal to the
voltage across the inductor DCR.
Figure 21: DCR Current Sensing
A current proportional to the inductor current in each
phase is generated and used for per-phase current
balancing. The individual phase current signals are
summed to arrive at the total current.
The phase currents and total current are quantized by
the monitoring ADC and used to implement the
current monitoring and OCP features. The total
current is also summed with the VID DAC output to
implement the AVP function.
The recommended value for C_sen is 220nF, with an
NPO type dielectric. To prevent undershooting of the
output voltage during load transients, the R_sen resistor
can be calculated by:
1.05 * L _ out
R_sen  _{Csen  DCR}
Note: Use thick film resistor (0603) for Rsen.
12V
VCC_Core
PWM
V cc
V in
P WM
BOOT
I Iphase
+
-
IS EN
IRTN
R1
10K
2.49K
R2
IR3555
S witch
IO UT
REF IN
L_out
Figure 22 RDS (ON) Current Sense
Additionally, the current sense inputs to the IR35203
can also be directly fed the current information from a
26 ^{www.irf.com | © 2016 International Rectifier}
February 8, 2016 | V1.5