Pin Description
MAX1917
Tracking, Sinking and Sourcing, Synchronous Buck
Controller for DDR Memory and Termination Supplies
8 _______________________________________________________________________________________
CURRENT LIMIT vs. TEMPERATURE
MAX1917 toc16
TEMPERATURE (°C)
CURRENT LIMIT (A)
806020 400-20
2
4
6
8
10
12
14
16
18
0
-40 100
R
ILIM
= 402kΩ
R
ILIM
= 200kΩ
MAX1917 toc17
V
IN
(V)
INDUCTOR CURRENT (A)
13119753
10
12
14
16
18
8
115
INDUCTOR PEAK AND VALLEY CURRENT
vs. INPUT VOLTAGE AT CURRENT LIMIT
I
PEAK
I
VALLEY
CIRCUIT OF FIGURE 3
R
ILIM
= 400kΩ
Typical Operating Characteristics (continued)
(V+ = 12V, V
OUT
= 1.25V, T
A
= +25°C, unless otherwise noted.)
PIN NAME FUNCTION
1 EN/HSD
Enable/High-Side Drain. Connect to the high-side N-FET drain for normal operation. Leave unconnected or
connect to GND for low-power shutdown.
2 DDR
DDR Reference Input. An applied voltage at DDR sets V
VTT
and V
VTTR
to 1/2V
DDR
. DDR voltage range is
from 0 to 3.6V.
3 POK
Power-OK Output. POK is an open-drain output and is logic high when both VTT and VTTR are within 12%
of regulation. POK is pulled low in shutdown.
4 VTT VTT Feedback Input. Connect to VTT output.
5 ILIM
Current-Limit Threshold Adjustment. Connect a resistor from ILIM to GND to set the current-limit threshold,
or connect ILIM to VL for default setting. See the Setting the Current Limit section.
6 FSEL Frequency Select. Selects the switching frequency of the MAX1917. See Table 1 for configuration of FSEL.
7 REF Reference Bypass. Connect a 0.22µF or larger capacitor from REF to GND.
8 GND Ground
9 VTTR
VTTR Reference Output. Connect a 1µF or larger capacitor from VTTR to GND. VTTR is capable of
sourcing and sinking up to 25mA.
10 V+
Input Supply Voltage. Supply input for the VL regulator and the VTTR regulator. Bypass with a 0.22µF or
larger capacitor.
11 VL
Internal Regulator Output. Connect a 2.2µF or larger capacitor from VL to GND. VL can be connected to
V+ if the operating range is 4.5V to 5.5V.
12 DL Low-Side MOSFET Gate Drive. Connect to the gate of the low-side N-channel MOSFET.
13 PGND Power Ground
14 BST
Bootstrapped Supply to Drive High-Side N-Channel MOSFET. Connect a 0.47µF or larger capacitor from
BST to LX.
15 DH High-Side MOSFET Gate Drive. Connect to the high-side N-channel MOSFET gate.
16 LX Inductor Switching Node
