MAX1717 Maxim, MAX1717 Datasheet - Page 10

• Manufacturer Part Number: MAX1717
• Description: Dynamically Adjustable / Synchronous Step-Down Controller for Notebook CPUs
• Manufacturer: Maxim

Dynamically Adjustable, Synchronous
Step-Down Controller for Notebook CPUs
10
(Circuit of Figure 1, components of Table 1, V+ = +12V, V
PIN
1
2
3
4
5
6
7
______________________________________________________________________________________
SKP/SDN
NAME
TIME
FBS
V
CC
V+
FB
CC
A
B
C
300kHz VOLTAGE POSITIONED, CIRCUIT 2,
PWM MODE, NO LOAD
A = V
B = INDUCTOR CURRENT, 10A/div
C = SKP/SDN, 5V/div
OUT
Battery Voltage Sense Connection. Connect V+ to input power source. V+ is used only for PWM one-shot
timing. DH on-time is inversely proportional to input voltage over a range of 2V to 28V.
Combined Shutdown and Skip-Mode Control. Drive SKP/SDN to GND for shutdown. Leave SKP/SDN open for
low-noise forced-PWM mode, or drive to V
causes inductor current recirculation at light loads and suppresses pulse-skipping operation. SKP/SDN can also
be used to disable over/undervoltage protection circuits and clear the fault latch by forcing it to 12V < SKP/SDN
< 15V (with otherwise normal PFM/PWM operation). Do not connect SKP/SDN to > 15V.
Slew-Rate Adjustment Pin. Connect a resistor from TIME to GND to set the internal slew-rate clock. A 470kΩ
to 47kΩ resistor sets the clock from 38kHz to 380kHz, ƒ
Fast Feedback Input. Connect FB to the junction of the external inductor and output capacitor for nonvolt-
age-positioned circuits (Figure 1). For voltage-positioned circuits, connect FB to the junction of the external
inductor and the positioning resistor (Figure 3).
Feedback Remote-Sense Input. For nonvoltage-positioned circuits, connect FBS to V
load. FBS internally connects to the integrator that fine tunes the DC output voltage. For voltage-positioned
circuits, connect FBS directly to FB near the IC to disable the FBS remote-sense integrator amplifier. To dis-
able all three integrator amplifiers, connect FBS to V
Integrator Capacitor Connection. Connect a 100pF to 1000pF (470pF typ) capacitor from CC to GND to set
the integration time constant. CC can be left open if FBS is tied to V
Analog Supply Voltage Input for PWM Core. Connect V
series 20Ω resistor. Bypass to GND with a 0.22µF (min) capacitor.
, 1V/div
SHUTDOWN WAVEFORM
100µs/div
Typical Operating Characteristics (continued)
DD
= V
CC
CC
= SKP/SDN = +5V, V
for normal pulse-skipping operation. Low-noise forced-PWM mode
FUNCTION
CC
.
CC
SLEW
A
B
C
to the system supply voltage (4.5V to 5.5V) with a
300kHz VOLTAGE POSITIONED, CIRCUIT 2,
PWM MODE, I
A = V
B = INDUCTOR CURRENT, 10A/div
C = SKP/SDN, 5V/div
OUT
= 150kHz
OUT
= 1.6V, T
, 1V/div
SHUTDOWN WAVEFORM
CC
OUT
.
·
= 12A
120kΩ / R
100µs/div
A
= +25°C, unless otherwise noted.)
Pin Description
TIME
OUT
.
directly at the